# Poorman's guide to Vacuum Testing



## Four Paws (Jan 18, 2007)

Well, I have learned a thing or two from this site, so I figured I would give something back. We all talk about vacuum testing crankcases to determine if a saw has an air leak. Seems as if the "how do I vacuum test my saw" question gets asked quite often here, so I put together a step-by-step pictorial guide. 

The first thing you need is a vacuum bleeder. Since we are doing this on the cheap, you probably don't want to fork out the money for a Mity-Vac, so this model from Harbor Freight works just fine, and is currently on sale for $17, normally $25.







Now, you will need to determine how you are going to hook the vacuum bleeder up to your saw. I made this handy adapter to hook into my impulse hose on the saw I am working on. Cost me $2.50 - $1.25 for each nipple, and I had the connector laying around in my box of parts.






Okay, now you need to block the intake and exhaust ports. This step requires some disassembly of the saw, but I am assuming that if you are vacuum testing your crankcase, you feel comfortable taking your saw apart. I used some rubber from a rim strip - covers the spoke nipples on the inside of a dirtbike wheel - you can also use an old bicycle inner-tube, gasket paper, etc. Cut the pieces to length, use your exhaust and intake gaskets as a template to transfer the bolt holes to the rubber, and use a punch or leather working tool (like I used) to punch holes in the rubber. 






Now, this piece of rubber will be insterted, as a gasket would, on your intake/exhaust ports. The only difference is the rubber covers the ports. Now, install your muffler and intake boot and sandwich the rubber gasket between the ports and the muffler/intake boot. You can see the rubber gaskets I made, installed as I described, in the pictures below. If you have a spigot mount carb, you can use a piece of innertube and a hose clamp to seal the intake. 











Now, make sure your spark plug is installed and hook up your vacuum bleeder to the impulse hose. 






Looks like you are ready to go to work. Pump the vacuum bleeder until you reach your desired vacuum. 






Go have a beer  then come back in 5 minutes or so, and check to see if your vacuum gauge is reading the same as when you left it...hopefully it is. Now, rotate the crank slowly by hand. Do this 5 times or so...is your vacuum still holding? If it is, GREAT! Now, port that big bore kit you bought, get it installed, file your chain and go make some chips!


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## KMB (Jan 18, 2007)

Thank you and good job. Nice clear pics, easy instructions, and done on a poor man's budget  . I've added the link to my favorites and will be referring back to it to do my 044 once I get all the parts and get it back together.

Kevin


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## kd460 (Jan 18, 2007)

Yes, very nice work and very nice pics. 

This one will be saved in my "chainsaw" files. 

Very timely as I am working on an 028 project saw, this will be a big help, thanks for taking the time to do this. KD


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## Lakeside53 (Jan 18, 2007)

GREAT JOB!!!!! I'm rep'd out for the day, but I'll hit you tomorrow!


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## Urbicide (Jan 18, 2007)

Nice job paws! Excellent pics!


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## Scooterbum (Jan 18, 2007)

Great step by step!!! Thanks :hmm3grin2orange: :hmm3grin2orange:


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## ASEMASTER (Jan 18, 2007)

real nice job thanks for taking the time to do so.


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## Justsaws (Jan 18, 2007)

Very nice!


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## 046 (Jan 18, 2007)

good job!


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## GASoline71 (Jan 18, 2007)

Thanks for that post FP!!! Nice clear pictures too!   

Gary


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## troutfisher (Jan 18, 2007)

VERY Impressive!!! Posts like that are the reason I visit this site daily, THANK YOU!!!!


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## Lakeside53 (Jan 18, 2007)

I know some of you are thinking "why rotate the crank 5 times..."


Many seals can be fine in one crank postion, but not another. I rotate them left and right a few times, and sometimes gently poke the seal when under vac. Don't exceed 0.4-0.6 bar though... you may get fake results.


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## Four Paws (Jan 18, 2007)

Thanks for the compliments guys! Just trying to help out. 

Andy, thanks for mentioning why I rotated the crank - I guess I took the reason for doing that for granted. For those that aren't good with conversions, .4 -.6 Bar = 11.8 -17.7 in-Hg.


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## Trigger-Time (Jan 18, 2007)

Thank you! rep is on the way


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## par38lamp (Jan 18, 2007)

*Rent a vacuum pump?*

Autozone rents vacuum pumps for free. That is a real poor man's way!


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## Sethro (Jan 18, 2007)




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## Urbicide (Jan 18, 2007)

John Dolmar said:


>


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## RiverRat2 (Jan 18, 2007)

*Fp!!!!!!*

Great post,,,, repped all good!!!!!!:rockn: :rockn: :rockn:


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## rahtreelimbs (Jan 18, 2007)

Hey Four Paws,

Did you pressure check as well???


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## Four Paws (Jan 18, 2007)

rahtreelimbs said:


> Hey Four Paws,
> 
> Did you pressure check as well???



Not this particular saw. It was just something I had apart on the bench and figured I would do a quick "how-to" write-up. The saw ran sweet, and there was no reason to suspect an air leak. Pressure testing is kind of like a security blanket, as 9 times out of 10, the saw will leak under vacuum before it leaks under pressure. "Poorman's guide to pressure testing" - Sounds like a good idea for a future write-up, LOL.


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## Tzed250 (Jan 19, 2007)

*Under pressure*

Yeah...I like to pressure test a 2-stroke CC just to get a second opinion. Nothing like some piece of mind.


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## mattinky (Jan 19, 2007)

You Rock Four paws, Thanks! Matt


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## Lakeside53 (Jan 19, 2007)

The only problem with a vac-only test is that it's often really hard to find where it's leaking.

Pressure testing is real good to find big or hard-to-see leaks... just keep pumping and get your ear down to the saw, or squirt with soapy water. I aways pressure test first, then vac.

When vac testing, and you have a slight leak that's hard to find, flip the saw on its side and drop light oil into the seal area. If it vanishes or stops leaking, that's your problem..

I also have a low pressure regulator to feed 3-5psi air to the saw under test - much easier to find the leaks that way than pumping - you can even dump the entire power head into to a 5 gallon bucket of water!


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## yawning_dog (Jan 23, 2007)

*Excellent!*

Four Paws, great job! Thanks for taking the time to put this together. I've been wondering if a brake bleeder would work and you've answered my question! So another one... where can you buy the little nipples that you've used to connect the bleeder hose to the impulse hose. Harbor Freight as well? Home Depot? Thanks!


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## Four Paws (Jan 24, 2007)

yawning_dog said:


> where can you buy the little nipples that you've used to connect the bleeder hose to the impulse hose. Harbor Freight as well? Home Depot? Thanks!



Yes, you can buy them at HF, Home Depot, any industrial tool supply store. Any place that sells air compressors/air tools should have them.


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## lumberjackchef (Jan 24, 2007)

Thanks for all of the detailed info. Now I know what I'm off to do for the day. I've got an old 1716 skilsaw that has all of the syptoms of an airleak. Watch out now cause I'm armed and dangerous. The best thing to do with that first cup of coffee, a side order of AS. First cup  , second cup:biggrinbounce2: ,now after a side of AS :hmm3grin2orange:


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## pioneerguy600 (Mar 8, 2008)

Really good job on the post Four Paws,very clear instructions. If the saw you are working on does not have an impulse line you may need another way to connect the vac or pressure line up to.I use a fitting that screws into the spark plug hole,it is homemade from an old spark plug base and a hose nipple just made them fit together and soldered them,brass to clean steel. Also use two air hold fittings that are meant to hold valves closed on four strokes if seals or springs need replacing and you don`t want to pull the head.A air hose coupler makes connecting the low pressure air supply line easy. Pioneerguy600


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## nicklt040 (Mar 8, 2008)

Hey 
I just bought one of those pumps from the parts store today. Got the fittings and kinda gave up after that. This is the best == THE BEST post i've seen on here yet.     :blob4:


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## Freakingstang (Mar 8, 2008)

Good Job Josh! Great productive post! We seem to have lost a lot of that lately...


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## brncreeper (Mar 9, 2008)

Nice work!


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## cmetalbend (Mar 9, 2008)

Four Paws said:


> Yes, you can buy them at HF, Home Depot, any industrial tool supply store. Any place that sells air compressors/air tools should have them.



Including most Wally worlds.


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## Poley4 (Mar 9, 2008)

Great job Josh! I need to vacuum test my 306A because it runs real erratic even after I rebuilt the carb. I already have a Mity-Vac, so a few fittings and I will be good to go. Thanks for the info!


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## Modifiedmark (Mar 9, 2008)

Poley4 said:


> Great job Josh! I need to vacuum test my 306A because it runs real erratic even after I rebuilt the carb. I already have a Mity-Vac, so a few fittings and I will be good to go. Thanks for the info!



By all means check it, but I had a 306a that was my main firewood saw for over 20 years and it always acted like it had a air leak when laid over on its right side. 

Had to feather it to keep it running for a second then it was fine. I checked if for leaks and even replaced the crank seals. No leaks were ever found and it ran forever that way. 

I think it was something in the Tilly carbs as I have a Jred 49sp that I just went through with a Tilly carb that still acts screwy when laid on its side also. 

Wish I knew


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## ale (Mar 9, 2008)

thanks for the write up and pics...this is why I love this site. Learning all I can about working on saws. great job.


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## oneadam12 (Mar 9, 2008)

Great info FourPaws


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## Airecon (Mar 9, 2008)

Seems like I've seen similar pumps that can pressure and vacuum test, but I may be wrong. Anyone know for sure?


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## masiman (Mar 9, 2008)

Airecon said:


> Seems like I've seen similar pumps that can pressure and vacuum test, but I may be wrong. Anyone know for sure?



Mityvac is one.


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## Poley4 (Mar 9, 2008)

Modifiedmark said:


> By all means check it, but I had a 306a that was my main firewood saw for over 20 years and it always acted like it had a air leak when laid over on its right side.
> 
> Had to feather it to keep it running for a second then it was fine. I checked if for leaks and even replaced the crank seals. No leaks were ever found and it ran forever that way.
> 
> ...



Thanks, I will check it out. I really like the way this saw cuts, but I hate it when you have to stay on the trigger just to keep it running and constantly needing to adjust the carb.


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## milkie62 (Mar 9, 2008)

How do you go about pressure testing the crankcase.Do all saws have the impulse line as stated in this thread to vaccum test ????


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## pioneerguy600 (Mar 11, 2008)

milkie62 said:


> How do you go about pressure testing the crankcase.Do all saws have the impulse line as stated in this thread to vaccum test ????



Hi milkie62; Not all saws have an impulse line. To connect the saws that do not have impulse lines you have to come up with a fitting that screws into the sparkplug hole. There may be a fitting that can be purchased with a hose barb fitting already on it but I made mine from a old spark plug . First break out the white porcelain insulator material,a couple cracks with a hammer works well, then clean up the area where the porcelain meets the metal base. Take a hose barb, the ones I use are made of brass ,and with a little filing or a lite grind make it fit into the base where the porcelain came out and then just solder together, use flux and 50/50 solder and any torch to just melt the solder and it will join tightly. Once done you have a fitting to connect your hose up to.For pressure testing you can just run a line from a compressor or any air supply but you will have to reduce the pressure to a couple of lbs as you don`t want to blow anything apart . I have a regulator from one of my paint guns that will regulate down to zero and set it for 2-3 lbs then apply air and then check for leaks .If you have a good ear you can hear where it is leaking, apply soapy water with a spray bottle to the crank seals ,the gaskets around the carb and spacers or boots ,the crankcase halves and the base gasket under the cylinder or the head gasket if there is one,
if they are leaking it will bubble and you have found your leak.
If you just want to test the crankcase to see if it holds pressure you would also need to have a hand pump,gauge and release valve, these can be bought as a kit and connect to the saw the same as above. Pump up some pressure ,10-12 lbs works for me and see how long it will hold, the longer the better but if it is not all leaked out in 20 seconds the saw will run all right. The vacuum test works better for me as this is what the saw is subject to under operation. If it does not hold vacuum then I apply air to find the leak.
This may answer your question , it is the way I do it, other mechanics may have a different method but it all serves to find one of the most common problems with small engines. Pioneerguy600


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## pdqdl (Feb 4, 2009)

*An update !*

I was referred to this post by another helpful member, and I thought I would update this thread.

I made a Word document that captures the images and text; now you can print it and save it for future reference. Unfortunately, I cannot upload it to AS, the file is too big!

I could break it into two parts, but that seems like a waste of time. Surely there is a better way. I tried zipping it, but there was not much difference in size.

Any suggestions on how this might be done?


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## 046 (Feb 4, 2009)

here's the lucky way.... craigslist.. $50
betcha that won't happen again...


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## teacherman (Feb 4, 2009)

I have found that Gorilla® brand duct tape is a quick and effective port sealer for this purpose. Goes right on the rubber manifold and the exhaust port of the cylinder. Clean area first, press it on hard, and it holds. Little or no residue deposits left behind. Nothing to fit or bolt.

(just waiting for Spacemule to twist these words around......):greenchainsaw:


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## teacherman (Feb 4, 2009)

pdqdl said:


> I was referred to this post by another helpful member, and I thought I would update this thread.
> 
> I made a Word document that captures the images and text; now you can print it and save it for future reference. Unfortunately, I cannot upload it to AS, the file is too big!
> 
> ...


Take a screen snapshot or two or three, and save them as jpegs and post them so they pop up automatically. Macs use Preview for the screenshot, not sure how a PC does it. Pretty quick and easy.

Or, anyone wishing to print it can do the same with the original post.


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## stihl only (Feb 4, 2009)

As was mentioned here before, make sure to do both a pressure and vac. Just because it will hold vacuum, doesn't guarantee it will hold pressure. Had an 038 MAG II here the other day that would hold vacuum for a month of Sundays, but the clutch side seal was leaking so bad you couldn't even pump the thing fast enough to get a reading.

For a real problem saw like this one, what Lake suggested with the regulator and a compressor is the ticket!


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## JONSEREDFAN6069 (Feb 4, 2009)

thanx for the tip, gonna put it to use on my 630.


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## teacherman (Feb 4, 2009)

stihl only said:


> As was mentioned here before, make sure to do both a pressure and vac. Just because it will hold vacuum, doesn't guarantee it will hold pressure. Had an 038 MAG II here the other day that would hold vacuum for a month of Sundays, but the clutch side seal was leaking so bad you couldn't even pump the thing fast enough to get a reading.
> 
> For a real problem saw like this one, what Lake suggested with the regulator and a compressor is the ticket!



I thought it was the other way around. Thanks for clearing that up.


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## AOD (Feb 4, 2009)

Some leaks/seals may hold under a vacuum but not under pressure, and vice versa. In A/C systems, they're pressurized to 200# to check for any leaks and hen drawn into a deep vacuum, at least 25" Hg, before being charged with refrigerant. These are far more extremes than anything found in the small engine world. Is a little leaking in a crankcase seal to be expected. In open drive refrigeration and A/C compressors a crankshaft seal is used and these can at best be called "leak resistant", they all leak some and its only a matter of time until they need replacement.


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## heimannm (Feb 4, 2009)

Thanks 4 Paws, should be just the inspiration I needed to go ahead and get the pump. 

I actually have two of the McCulloch 10 series parts kits for pressure/vacuum testing with the various plates, rubber seals, bushings, fittings, etc.

I also have a very suspicious John Deere/Echo saw on the shelf right now, a little testing should help conclude where the issues are or perhaps are not.

Mark

I assume if you don't remove and block the muffler you have to make sure the piston has the exhaust port covered?


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## pdqdl (Feb 4, 2009)

teacherman said:


> Take a screen snapshot or two or three, and save them as jpegs and post them so they pop up automatically. Macs use Preview for the screenshot, not sure how a PC does it. Pretty quick and easy.
> 
> Or, anyone wishing to print it can do the same with the original post.



Well... sure. But that doesn't serve the purpose I started with: Since printing from a thread gives clutter, tiny print, and poor control over the output, I tried to give folks something they could save and re-use.

There is no real gain in re-posting what was well done to begin with. By the way, I have incorporated some of the very good comments added by other people, so this file would be a small improvement on the original post.

If anyone wants this, private message me and I'll send it along. _(Unless I get thousands of requests!)_


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## skid row (Feb 4, 2009)

stihl only said:


> As was mentioned here before, make sure to do both a pressure and vac. Just because it will hold vacuum, doesn't guarantee it will hold pressure. Had an 038 MAG II here the other day that would hold vacuum for a month of Sundays, but the clutch side seal was leaking so bad you couldn't even pump the thing fast enough to get a reading.
> 
> For a real problem saw like this one, what Lake suggested with the regulator and a compressor is the ticket!



:agree2: :agree2:


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## briantutt (Apr 14, 2009)

pdqdl said:


> I was referred to this post by another helpful member, and I thought I would update this thread.
> 
> I made a Word document that captures the images and text; now you can print it and save it for future reference. Unfortunately, I cannot upload it to AS, the file is too big!
> 
> ...



Send the file to me at [email protected] I will get it up as a pdf.


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## Evan (Apr 29, 2009)

to the the top.

i did search and this theard didnt come up. not sure what good the search function is when old threads like this dont come up

bet it does now


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## briantutt (Apr 29, 2009)

pdqdl said:


> I was referred to this post by another helpful member, and I thought I would update this thread.
> 
> I made a Word document that captures the images and text; now you can print it and save it for future reference. Unfortunately, I cannot upload it to AS, the file is too big!
> 
> ...



:hmm3grin2orangeONE:hmm3grin2orange:


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## pdqdl (Apr 30, 2009)

That's great.

Four paws' excellent technical instructions, my own pretty good compilation of the notes he posted, and your nice conversion to a PDF.

Teamwork in action. 

You guys that read this need to save that PDF for the day when you need it.


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## Brian VT (Apr 30, 2009)

I just got a Mighty-Vac MV7000 at Sears for $35. I comes with all sorts of fittings, etc. I didn't need to buy any pieces/parts. Works great. 
Even better news is that my "problem saw" (MS360 Pro) seems to be tight. The mystery continues, but I'm narrowing down the suspects.
Good thread here. So much great info on this site.


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## milkie62 (Mar 9, 2010)

*working or not*

I picked up the tester from HF a couple of weeks ago.I put my finger over the fitting and gave it a few pumps but did not pull any vacuum on the guage.Do I assume the unit is no good ?


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## ric5141 (Mar 9, 2010)

I did the vacuum test on a Husky that was giving me lots of issues. Could not get any vacuum. Cobbled some more fittings (my compression tester has a screw in plug adapter with 1/4 coupling...sweet) put the bicycle pump and a fuul pump pressure tester on it and couldn't get it to hold any. Popped the flywheel and looked through the seal at the crank bearing! Man I have never seen a seal ripped up like that. 

Thanks for the info and tech advice. 

BTW Bearings and seals (units) are on their way


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## Arrowhead (Mar 9, 2010)

milkie62 said:


> I picked up the tester from HF a couple of weeks ago.I put my finger over the fitting and gave it a few pumps but did not pull any vacuum on the guage.Do I assume the unit is no good ?



I would say its junk.


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## stihl_ (Jun 28, 2010)

*Vacuum Tester*

You are lucky to get the vacuum tester for $17, they are about $170 in Australia.


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## Jbevs (Sep 1, 2010)

Thanks to four paws and the guys that made it in to a PDF.


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## teatersroad (Sep 1, 2010)

I was just here a couple days ago, yup, thanks fourpaws. 

Poorer man's test kit ended up being: I had a gauge, picked up a 60mL syringe at the feed store for a buck fiddy, some hose and a tee fitting for another buck. Pulls 6" of vacuum and pushes 5 psi on my 60cc saw.


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## pippin5267 (Sep 1, 2010)

This is one of the most informative and easy to read posts I've ever read on this site. Its very easy to understand and has good clear pictures. Heres a rep for you.


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## Jaberwky (Oct 14, 2010)

*For Stihl saws?*

The exhaust seal is simple, but on my Stihl 460 I can't bolt the intake seal on like in the photos. I'm stuck with the big long carb-mounting studs with only the ends threaded. I need some kind of plate/washer and super long sleeves to go over the studs enough to press the seal and also allow me to tighten the bolts down.

Suggestions from Stihl owners?


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## USMC0802 (Oct 14, 2010)

Jaberwky said:


> The exhaust seal is simple, but on my Stihl 460 I can't bolt the intake seal on like in the photos. I'm stuck with the big long carb-mounting studs with only the ends threaded. I need some kind of plate/washer and super long sleeves to go over the studs enough to press the seal and also allow me to tighten the bolts down.
> 
> Suggestions from Stihl owners?



I went to the local hardware store and picked up a pair of these. I think I took the tank handle or even the entire saw carcass with me to check the size (length and diameter of the opening) for the carb studs. I also grabbed a few washers. Picking up some aluminum stock would be a good idea as well. It's easy to cut with a hacksaw and it's cheap.


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## briantutt (Oct 14, 2010)

Jaberwky said:


> The exhaust seal is simple, but on my Stihl 460 I can't bolt the intake seal on like in the photos. I'm stuck with the big long carb-mounting studs with only the ends threaded. I need some kind of plate/washer and super long sleeves to go over the studs enough to press the seal and also allow me to tighten the bolts down.
> 
> Suggestions from Stihl owners?



maybe cut off an aluminum arrow shaft?


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## kam (Oct 14, 2010)

Jaberwky said:


> The exhaust seal is simple, but on my Stihl 460 I can't bolt the intake seal on like in the photos. I'm stuck with the big long carb-mounting studs with only the ends threaded. I need some kind of plate/washer and super long sleeves to go over the studs enough to press the seal and also allow me to tighten the bolts down.
> 
> Suggestions from Stihl owners?





In electronics, they use stand offs to lift a circuit board away
from a metal chassis. Buy from electronics parts stores, or possibly Home Depot hardware section. Or salvage from discarded equipment.

Mine are pictured between the two gauges. (silver tubes)


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## RENNIE (Nov 2, 2010)

USMC
What the hell is that between the 2 & 2 1/2" mark??????


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## K5krawler (Jul 1, 2011)

Four Paws said:


> Go have a beer  then come back in 5 minutes or so, and check to see if your vacuum gauge is reading the same as when you left it.



It takes you 5 minuets to drink a beer lol! J/K!!! Do you or anybody else here have any type of condemning limits for a leak down test. As in a drop of XXX in/Hg over X:XX ? 

K5


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## mifirewoodguy (Jul 22, 2011)

Lakeside53 said:


> The only problem with a vac-only test is that it's often really hard to find where it's leaking.
> 
> Pressure testing is real good to find big or hard-to-see leaks... just keep pumping and get your ear down to the saw, or squirt with soapy water. I aways pressure test first, then vac.
> 
> ...


 
Gosh! I love you guy! lol!


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## o8f150 (Sep 2, 2011)

fantastic thread,, i just learned something too


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## thook (Sep 14, 2011)

Great thread!

I gotta a question not covered here in the thread.

I don't have an impulse line on my Makita 520i. So, I'm gonna have to rig something up to test vac and pressure. I'd just recently installed a new ring because the piston and cylinder scored. Not a lot of transfer....easily cleaned up. The cylinder's smooth as silk except just below the exhaust port on one corner. Even then, barely noticeable.

I'm still reading and learning as to why this may have happened and what to do to prevent it from happening, again. I read somewhere about the saw running lean. So, I figure check the vac and press. test to make sure no seals were leaking.(It was having some running problems before getting serious and not running hardly at all). But, I just put in the new ring. Should I break in the new ring first before running the tests, or just go ahead do it?


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## thook (Sep 15, 2011)

Well, since no one answered and I couldn't find any definitive info, I thought about it and I'm gonna guess it doesn't matter. Ring or no ring, neither vac or press. should be leaking past any seals in the case or cylinder head. Given part of the instruction is to rotate the crank several times over, the ring question is moot. Is this correct?


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## 72thing (Sep 15, 2011)

thook, I'm new at the vac/press testing thing, too. But, having just tested my 036, I'm confident in doing it again. If all you're doing is testing the crankcase, it won't matter if there's even a piston in it, lol--as long as the cylinder is sealed tightly to the case. Definitely pressure test it first to make sure you don't have any leaks with your blockoffs, etc. And don't forget to look for leaks around the sparkplug!! Mine leaked around the plug and it threw off my test until I discovered it. I used soapy water (LOTS of Dawn) to spray around everything. If it pressure tests ok, _then_ vacuum test it. Make sure you have the clutch assy, etc and the flywheel off so you can actually _see_ the oil seals. I know that's pretty obvious, just sayin'. :deadhorse:

Will


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## thook (Sep 15, 2011)

72thing said:


> thook, I'm new at the vac/press testing thing, too. But, having just tested my 036, I'm confident in doing it again. If all you're doing is testing the crankcase, it won't matter if there's even a piston in it, lol--as long as the cylinder is sealed tightly to the case. Definitely pressure test it first to make sure you don't have any leaks with your blockoffs, etc. And don't forget to look for leaks around the sparkplug!! Mine leaked around the plug and it threw off my test until I discovered it. I used soapy water (LOTS of Dawn) to spray around everything. If it pressure tests ok, _then_ vacuum test it. Make sure you have the clutch assy, etc and the flywheel off so you can actually _see_ the oil seals. I know that's pretty obvious, just sayin'. :deadhorse:
> 
> Will



Right'o. I'd figured all that, but I do appreciate the feedback, Will. Thanks!


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## SkippyKtm (Sep 15, 2011)

Good 'ol four paws, what ever happened to him? He hasn't been here for nearly a year and a half.

Truly a great thread, he is a lost asset to Arboristsite...


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## Edge & Engine (Sep 15, 2011)

We have a Mityvac pressure/vacuum pump available now for $45.95.
Mityvac [MVC MV8255] Mityvac Selectline MV8255 Vacuum/Pressure Pump - $45.95

We've been using this model in our shop for the past 8 months or so, it's a nice unit..


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## thook (Sep 17, 2011)

*Makita dcs520i: Vacuum/pressure test*

So, I finally got around to doing the deed today. I took all the info supplied in this thread into account when figuring my methodology. 

I used the bicycle inner tube gaskets......only, instead of going the somewhat more involved route of modifying a spark plug as the testing point, I cut the valve stem section of the tube and used the valve stem to hook up the testing tools.

First, I tried installing the valve stem/gasket at the intake port with the valve stem protruding through the carb boot, but that proved to be inadequate in two ways. One simply because I didn't have the right length of bolt needed to mount the carb boot over the gasket.....and consequently stripped some threading in the cylinder head.....though not beyond being able to still mount the carb. Two, and more importantly, the inner tube is thicker around the valve stem. Being that the intake port is so small, the carb boot would not sit flush enough to give a proper seal. So, I moved it to the exhaust port and made a block off plate of aluminum stock drilling a hole in the center so the valve stem would protrude. On the intake side, I simply made a flat gasket of the tube and installed the entire carb ass'y over it. As well, per Stumpyhusky's suggestion , I applied a light coat of grease to both mating flanges. It all sealed very well. 

To pressurize everything, I used an old, but functional, Rock Shox suspension fork pump. It's rather slender, lightweight, and has a gauge and pressure release valve. One full pump and the case/cylinder was up to 50psi.(No...nothing blew up). So, I let some air out, and after 1 minute no pressure had escaped even after several rotations of the crank.

Then, I removed the pump, removed the inner valve from the stem, and applied the vac pump. Again, after 1 minute and several rotations, no air had escaped. All's good with Makita!

I used a schrader type valve stem. I figure, though, one could get a bit fancier and use a presta type valve with a schrader adapter if using a schrader fitting on the pressurizing tool. The presta valve would allow one to actually fasten the valve stem to a block off plate via the circular nuts normally used to tighten the valve stem to bicycle rim. Fancy, but not really necessary.

Anyway, my little addition. Thanks for the great write up!


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## ft. churchill (Feb 29, 2012)

Thank you for this post as it gives ya all the needed ideas an know how to do this important check.


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## Dan Forsh (Mar 13, 2012)

I've been reading this thread for a while now with the intention of getting set up to do pressure/vac testing. I never used to pay too much attention to those who would always reply to any running issue with "pressure and vac test it". 

Now I realise this is really good advice and a very simple common sense starting point when working on a saw, especially for those of us who buy them broken, history unknown.

So initially I was thinking that the Mityvac was the way to go, but unfortunately these aren't the most common here in the UK and sellers seem to know this and certainly price the pressure/vac model like they're rocking horse manure.

I didn't want to have two different set ups so I found a new compound gauge with a 4" dial on ebay quite cheap and our friendly maintenance fitter at work supplied the fittings I have up to now.






Not exactly compact but I won't have any trouble reading the dial. I've bought one of those bulb type blood pressure pumps on ebay but this is gonna be a while as it's coming from China, so I should be geared up for pressure. The one thing I haven't yet worked out is what I'm going to use for vacuum.

Any ideas on a cheap vacuum pump anyone? I suppose I could look for a really cheap brake bleeder maybe? When I type in hand vacuum pump on ebay most of what comes up seems to be a pump attached to a clear plastic cylinder with inches marked on the side "From United States", go figure?

I'll post a pick of the finished assembly once I have it all together.


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## Eccentric (Mar 13, 2012)

Dan Forsh said:


> I've been reading this thread for a while now with the intention of getting set up to do pressure/vac testing. I never used to pay too much attention to those who would always reply to any running issue with "pressure and vac test it".
> 
> Now I realise this is really good advice and a very simple common sense starting point when working on a saw, especially for those of us who buy them broken, history unknown.
> 
> ...



There's gotta be some kind of hand opperated vacuum pump available to you folks in the UK. The Mityvac is what we get here in the States. Must be an equivelant on your side of the water. Go to a UK automotive enthusiast site and see what they're using.........or you could just into your local car repair shop and ask them what they use and where they got it.


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## captoaklog (Mar 13, 2012)

Niiiiiice work....thank you for the time


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## SkippyKtm (Mar 14, 2012)

This is a wee bit off topic but does anyone know what happened to Four Paws? He just kind of vanished back in January of 2009...


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## kev1n (Mar 14, 2012)

That's a nice gauge, I have on similar and would like to buy a new one. Did the seller have more available or was it a one time deal? Mine is a bulb type pump that you just flip around to do vacuum. I'd like to find a new one of those as well, Here is something similar to the one I have.

Kevin
Heathrow Scientific HD20631B Vacuum/Pressure Bulb without Tubing, 85mL Capacity, Rubber:Amazon:Industrial & Scientific


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## Dan Forsh (Mar 14, 2012)

Eccentric said:


> There's gotta be some kind of hand opperated vacuum pump available to you folks in the UK. The Mityvac is what we get here in the States. Must be an equivelant on your side of the water. Go to a UK automotive enthusiast site and see what they're using.........or you could just into your local car repair shop and ask them what they use and where they got it.



I'm not saying I can't buy Mityvac, I could now just buy the basic vacuum model without a gauge (roughly about 45-50 USD), but I'm being kind of pig headed now; I decided to not buy the bells and whistles Mityvac and opted to try to build my own for cheap, so I would feel like I caved if I bought one now (still might though:msp_smile.



kev1n said:


> That's a nice gauge, I have on similar and would like to buy a new one. Did the seller have more available or was it a one time deal? Mine is a bulb type pump that you just flip around to do vacuum. I'd like to find a new one of those as well, Here is something similar to the one I have.
> 
> Kevin
> Heathrow Scientific HD20631B Vacuum/Pressure Bulb without Tubing, 85mL Capacity, Rubber:Amazon:Industrial & Scientific



Sorry Kevin, I just checked and the seller doesn't have any other gauges for sale, I think it was a 1 off, new old stock. Thanks for the lead on the bulb pump though, that might be an option if I can source similar over here.


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## Eccentric (Mar 15, 2012)

Wow. We can get the 'bells&whistles' Mityvac for $40 USD or less.


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## heimannm (Mar 15, 2012)

A large syringe from a farm fleet place or animal health supply works pretty well for most jobs and cna create pressure or vacuum depending on where the plunger is when you connect it. 

Think large as in horses, cows, or I suppose water buffalo and elephants if you're in Asia some where.

As other have reported, $1.50 each or a three pack for $4 depending on where you find them.

Mark


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## K5krawler (Apr 28, 2012)

*Regulator & Gauge*

This is my set up which includes a the quick connect at both ends so I can put this inline and have regulated pressure to my small blow gun. The small blow gun works great for fitting into the impulse lines on most saws. I've used it once and it works really nice and once the regulator is set, all I have to do it plug it in and verify that I am at 10 PSI and we are golden.


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## nstueve (Aug 14, 2012)

Just got the MV8500 kit online cause i found it cheap and un-used... Needed one for a while but I'm still not seeing any specific info in this thread about leak/vac limits. 

Guessing 6-12psi to pressure test will get the job done and help find leaks... Should the amount of pressure you use depend on the saw or will 6-12psi be good for just about any saw?

Also, is there a bleed rate when you vaccuum check that we should be looking for? A bench mark number to go by? ie: after 1min leak is >4psi you need to find and fix leak?

Another idea for attaching your vac pump to a saw with no impulse line is to get a plastic piston stop. Drill a hole down the length of it. Add a o-ring between the top and the threads to stop air leak. Screw in a brass connector like seen in other photos, to the top of the piston stop (to attach the vac hose). You can also chop the bottom of the stop off to allow the crank to rotate. Cheap and easy way to make a spark plug adaptor. I recommend a drill press for drill the hole down the length of the piston stop.


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## heimannm (Aug 14, 2012)

I just knocked the insulator out of a spark plug and tapped the base for a 1/4" pipe fitting and installed a barbed connector. Works slick.

K5 - you have to disconnect the air supply and make sure it will hold pressure, testing the crankcase for vacuum or pressure has to be static, not dynamic. Your rig would work for a leak down if you included a flow meter, but even a simple one costs about $175.

Mark


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## arrow13 (Sep 29, 2012)

*Pressure and Vac testing methods*

Outstanding info. Thanks everyone. This will undoubtedly help me keep my saws running well. Currently working on an 076 Super with what I believe is an air leak. Got one of the Stihl vac/pressure testers via ebay recently to use for this project, and my other saws.
Will


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## sawlog1992 (Sep 29, 2012)

*WOW- I wish this could be put somewhere it woul be easy to find*

Now I am off to see what "SQUISH" is


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## Moparmyway (Dec 21, 2012)

sawlog1992 said:


> Now I am off to see what "SQUISH" is


If you dont have the manual to determine the correct bolt torque, then Squish is "when you think its squished enough, squish it a little more" ......................If you have the manual, follow it !


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## Fish (Dec 21, 2012)

sawlog1992 said:


> Now I am off to see what "SQUISH" is



That is how I got married the first time!


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## Fish (Dec 21, 2012)

Fish said:


> That is how I got married the first time!



Well, maybe more.....


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## PogoInTheWoods (Dec 21, 2012)

Fish said:


> That is how I got married the first time!



Evidently without the latest torque specs.


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## president (Jul 11, 2013)

kudo's will be on top drawer in the whitehouse secret file drawer


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## mikerecike (Jan 10, 2015)

Where will i find the four paws vac test pdf? Thanks


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## tntblaster14 (Feb 16, 2015)

So I'm sorta new to vac testing. Got my 346 sealed up, it will pass pressure but not vacuum. So obviously a leak somewhere. How do you find the vac leak? Smoke? Dunk the whole saw in water (really don't wanna do this one), or something else?


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## gunnusmc03 (Feb 16, 2015)

I spray the suspected leak areas with windex and look for bubbles.


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## PogoInTheWoods (Feb 16, 2015)

I use a dish soap and water spray mix to look for bubbles. I _have_ dunked a whole case in a tank of water before to identify a particularly mysterious and pesky leak. (Not an uncommon practice, btw.) With the carb removed, block everything off and apply low pressure _before_ immersion to minimize water getting in anywhere. I found the leak right away, though a little water did manage to get into the oil tank through the oil passage (which I forgot to block). The saw happened to be a 55 Rancher with the notorious intake issues, which is indeed where the leak was. My fault, actually, as I managed to pinch the impulse tube putting the intake assembly into position on the cylinder. Fixed that, blew out the cylinder and case with compressed air afterward for good measure, and headed on down the road with another leak-free (and very clean!) saw.


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## heimannm (Feb 16, 2015)

Post #99 - if the problem is a vacuum leak you may want to avoid dunking it...perhaps a drop of oil on the seals one at a time and see if that does it, at least then you will know where to investigate.

Mark


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## Moparmyway (Feb 16, 2015)

heimannm said:


> Post #99 - if the problem is a vacuum leak you may want to avoid dunking it...perhaps a drop of oil on the seals one at a time and see if that does it, at least then you will know where to investigate.
> 
> Mark


I agree 100% and have never dunked anything. Oil will get sucked in to a leak and is a great way to find a pesky leak under vacuum. If the oil disappears or the vacuum holds, you have found your leak.


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## PogoInTheWoods (Feb 16, 2015)

Not trying to be difficult or contentious here, but...

I agree with the oil (or grease) approach for a vac leak as well -- depending on the convenience/practicality of applying the method to a given suspected area. Seals are obviously easy as are most cylinder bases and case gasket areas. Intakes on some saws can sometimes be a bit more difficult to navigate due to visual restriction with even the soapy water method for a pressure test, let alone the oil/grease method for a vac test. Realizing that a one-way leak is a bit more tricky as it actually represents a 'valve' in its function, on a saw, a vac leak will usually translate into a pressure leak under the right circumstances with enough pressure -- which doesn't necessarily mean crank up the compressor until the seals pop. Rotate the crank, flex the intake assembly, twist the handle/tank against the case mounts, etc. You'll usually find a pressure leak if there's a vac leak and usually with the soapy water method.

Also make sure your vac and pressure levels are appropriate and not way into overkill land....., and ensure that any home brew testing rig itself isn't the problem and providing erroneous results. Personally, I use a MityVac 8500. Paid around 50 bux for it. Does vac or pressure with the flip of a knob.

I'm just saying if all else fails for me, I'll dunk a case any day to find a leak fully realizing the risks and considerations and not look back. The key is already having pressure in the case when doing so and ensuring the integrity of the case and cylinder afterward relative to moisture/water infiltration. It's a last resort method for sure, but one that is effective if carefully implemented and been successful for me. Mileage may vary for others.

But in this case, I'd be suspecting the decomp anyway since it is indeed a valve by design and enough pressure would tend to 'close' it and enough vac would tend to 'open' it....or dislocate enough carbon or other small debris in either direction in the valve to simulate same.

Good luck 'tnt'. Be interested to learn what you end up doing and what you discover.

Just tryin' to help.


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## heimannm (Feb 16, 2015)

vacuum leaks suck

Mark


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## PogoInTheWoods (Feb 16, 2015)

And pressure leaks blow.....

And all too often we overlook the simplest and most obvious causes and solutions.


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## tntblaster14 (Feb 16, 2015)

Yea i'm a little bit slow on the repairs right now, been spending pretty much everyday outside w/ the cattle, or equipment has been breaking down in this wicked cold weather (spent 6 hours outside straight bare handed today fixing tractor).. or w/e is busted in this cold weeather. It never goes down in nice 40F days no... on the 4F days haha...

so the chainsaw repairs are like.. back burner right now since I have mild tingling in most of my fingers all night right now lol. I picked up a 1991 and 1999 346xp really cheap and am practicing taking them apart.. slowly ! One has a scored piston so obviously an air leak, and I have the Mityvac 8500.. and it is pretty sweet device. Can even bleed brake lines easily


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## JWG (May 24, 2015)

Four Paws said:


> Well, I have learned a thing or two from this site, so I figured I would give something back. We all talk about vacuum testing crankcases to determine if a saw has an air leak. Seems as if the "how do I vacuum test my saw" question gets asked quite often here, so I put together a step-by-step pictorial guide.
> 
> The first thing you need is a vacuum bleeder. Since we are doing this on the cheap, you probably don't want to fork out the money for a Mity-Vac, so this model from Harbor Freight works just fine, and is currently on sale for $17, normally $25.
> 
> ...





KMB said:


> Thank you and good job. Nice clear pics, easy instructions, and done on a poor man's budget  . I've added the link to my favorites and will be referring back to it to do my 044 once I get all the parts and get it back together.
> 
> Kevin


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## president (May 24, 2015)

gunnusmc03 said:


> I spray the suspected leak areas with windex and look for bubbles.


you must have watched that great big fat greek wedding movie 
and dad with his windex fetish


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## gomoto69 (May 24, 2015)

here's everything i used for my first vac/pressure test performed recently on a jred 2171. My vac pump was leaky, so i tee'd in the mac vac/pressure guage, and would pinch off the line to the vac pump after pumping it up to avoid losing vacuum thru the pump. I already had an air line brazed to a spark plug bidy i had used years ago ti replace valvesprings on a 340 mopar i have without removing the heads. Used innertube to block carb, and innertube plus a blockoff plate for exhaust. First prrssure test i couldn't find a leak, but i think i was expecting a much bigger, louder sound of escaping air. Would only hol vac with crankshaft in one position, bled off quickly when turned. Only then did i remove clutch and flywheel, and next pressure test showed obvious leakage (bubbles) around both seals. Replaced seals, good to go now!


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## PeterM (Oct 2, 2015)

I can not see the images, but the only one I need to see the "handy adapter to hook into my impulse hose" 
I see other images on the website, but these all have generic icon . 
Anyway, I need to check the pressure and vacuum on my saw as I have replaced piston and still can not start the saw. On the first pull, it sounds like it wants to start, but then nothing. I could pull the cord until I am blue in the face. 
Thanks!


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## Four Paws (Oct 2, 2015)

All of my original images were lost. The post above yours shows all that you need. 

Figure out a way to hook into your impulse hose and connect to your vacuum pump. I use a brass barbed fitting.


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## PeterM (Oct 2, 2015)

Thanks for the reply, I hope to stop at hf on the way home tonight. 
If you could explain what the impulse hose actually does, I would be very grateful. They call it a suction hose and valve. I noticed it when I was replacing the piston and cylinder, and could not find any information on it, nor could technical support be any help. I really appreciate your feedback and this website is great!


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## Four Paws (Oct 2, 2015)

What saw?

Impulse hose is open to the crankcase and transmits a positive or negative pressure to the carburetor to pump fuel.


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## PeterM (Oct 3, 2015)

it is a Blue Max, 18". The suction hose itself (it is black) appears intact, there is a asbestos sleeve around it that has been singed in a couple of spots. This hose connects to a brass valve one end and on the other end, to the carburetor. I did try to see if it were clogged, and I blew into it, an also was able to draw air by sucking. 
I called Blue Max earlier this week, and they eventually said I should replace the valve, even though the engineer at NATI Tools there wasn't any way to test it.
What do you think? 
I also put my thumb on the end of the hose and gave the saw a couple of pulls and could feel nothing, so then I checked here to see if I could learn a way to fix it.
thanks for your help!


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## xPosTech (Oct 6, 2015)

mikerecike said:


> Where will i find the four paws vac test pdf? Thanks


I too would like to find that PDF. It should have all of the images of the OP.

This was one post I was happy to see brought back from the past.

Thanks Four Paws for a great how to.

Ted


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## JonCraig (Dec 16, 2015)

Sorry to bump this, but any chance it could be updated with pics? Or does anyone have this pdf with the original pics?

I've never been satisfied with my vac/pressure setup and would like to see how it's done properly. Thank you!

--JC


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## PogoInTheWoods (Dec 16, 2015)

MityVac 8500 is the way to go. Various block-off plates and setups are up to you for your particular application, but a spark plug adapter for testing from the top down is very handy to have as an alternate approach in any number of situations, especially if you only want to check your case and seals. Gorilla Tape at the intake and exhaust on clean surfaces provides more than an adequate seal for both vac and pressure tests of a case.


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## JonCraig (Dec 16, 2015)

Guerilla tape! Genius! Many thanks!

I have a mighty vac 8000 (the one that only does vacuum for brakes). Might have to upgrade to make the pressure test easy. 

When using the spark plug adaptor, the piston would need to be at the bottom of its stroke, right? That way the transfer ports are exposed/open?


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## briantutt (Dec 16, 2015)

I used Gorilla tape last time I blocked an intake. Works good.

Brian


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## PogoInTheWoods (Dec 17, 2015)

JonCraig said:


> Guerilla tape! Genius! Many thanks!
> 
> I have a mighty vac 8000 (the one that only does vacuum for brakes). Might have to upgrade to make the pressure test easy.
> 
> When using the spark plug adaptor, the piston would need to be at the bottom of its stroke, right? That way the transfer ports are exposed/open?



Can't take credit for the Gorilla tape. Read it somewhere else and just happened to have some to try. Was surprised, though it works better for vac than pressure for obvious reasons. For pressure testing, there are easy ways of doing that from a bicycle pump or a blood pressure bulb to just cranking the regulator down to around 5~10psi on an air compressor.

As for the piston position when using a spark plug adapter, I'm usually testing without a piston during a rebuild just to make sure the case and seals are tight before I even commit to installing the piston. Otherwise, I'm not sure it matters where the piston is. You should rotate the crank when doing a vac check looking for intermittent leaks on older seals anyway. Then again I've heard that not having the crank at BDC using a plug adapter renders the test useless. Not sure why it would. Guess it doesn't matter if you're using a block-off plate with a barb on the intake for testing or the impulse passage, tho.


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## CoreyB (Dec 19, 2015)

Interesting and youake it seem simple enough.


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## cruxmon (Nov 26, 2016)

There are several different pressure/vacuum test kits available for chainsaws on eBay, including OEM.


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## Deleted member 135597 (Nov 26, 2016)

cruxmon said:


> There are several different pressure/vacuum test kits available for chainsaws on eBay, including OEM.


Let me guess, you have some for sale and that's why your pulling up all these old threads. One thread would have been enough


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## SeMoTony (Nov 27, 2016)

tntblaster14 said:


> So I'm sorta new to vac testing. Got my 346 sealed up, it will pass pressure but not vacuum. So obviously a leak somewhere. How do you find the vac leak? Smoke? Dunk the whole saw in water (really don't wanna do this one), or something else?


water dunk is 2 show pressure leak, vacum would pull water into crank or other area ya don't want(-; my $.02


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## Big_6 (Nov 27, 2016)

I just picked up the harbor freight model, $25.


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## Baconaman (Feb 28, 2018)

cruxmon said:


> There are several different pressure/vacuum test kits available for chainsaws on eBay, including OEM.




I haven't looked through the entire thread, but the original pictures are no longer showing up in the beginning. Does anyone know how to access them?


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## Okie (Feb 28, 2018)

Baconaman said:


> I haven't looked through the entire thread, but the original pictures are no longer showing up in the beginning. Does anyone know how to access them?



I also noticed some more of his 11 year old pic's are not showing.
Did the Kodak instamatic film go bad/evaporate? (anyone got any good negatives they can re-post the pic's/)


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## HarleyT (Feb 28, 2018)

All of the old pics and vids are long gone.


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## teacherman (Mar 1, 2018)

tntblaster14 said:


> So I'm sorta new to vac testing. Got my 346 sealed up, it will pass pressure but not vacuum. So obviously a leak somewhere. How do you find the vac leak? Smoke? Dunk the whole saw in water (really don't wanna do this one), or something else?


I use Gorilla tape on the carb flange and the exhaust port, and put the vac pump on the imppulse line. A bit of vaseline on the impulse connection if that is suspect. If it leaks, I'd say the seals are the next step. Any opinions?


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## Paragon Builder (Mar 1, 2018)

teacherman said:


> I use Gorilla tape on the carb flange and the exhaust port, and put the vac pump on the imppulse line. A bit of vaseline on the impulse connection if that is suspect. If it leaks, I'd say the seals are the next step. Any opinions?



If it leaks, find the leak. Often pressurizing and some soapy water will tell you. Sometimes pressure holds and vac doesn’t. Lay the saw on its side and pour a little 2stoke oil on the seal. Either vac leak will stop, or it’ll suck the oil in. 

On occasion case gasket fails between oil and crankcase.


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## Okie (Mar 1, 2018)

teacherman said:


> I use Gorilla tape on the carb flange and the exhaust port, and put the vac pump on the imppulse line. A bit of vaseline on the impulse connection if that is suspect.* If it leaks, I'd say the seals are the next step. Any opinions?[/QUOTE]
> 
> If the saw is not holding pressure/vacuum, I do not just assume it is the crank seals. I try to confirm exactly where and how many leaks.
> If it is leaking I go to pressure and use soap and look for bubbles. I've found leaks in several places other than crankshaft seals.
> *


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## kz1000 (Mar 1, 2018)

Four Paws has moved on to become the resident vacuumologist at Husqvarna since the posting of this thread and all pictures have been archived at the United Nations museum for the preservation of chain saws.


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