# stihl ts420's and husqvarna k760's and k750 total rebuilds. best parts to use for $ other than OEM?



## ginsenger (Feb 19, 2017)

I am working for a masonry crew with about 20 or more saws. I am a retired master diesel mech, I know there are a few little things I need to know/learn about saws, at least I know that. The company has at least 10 Stihl ts420's and 10 husky k760's and a few k750's. The company doesn't want to spend the $ for OEM rebuild's. right now I have 5 huskys and 2 stihls that need total rebuilds. what is the best way to go for the money and still have a good solid saw that will take a beating and not make me look bad from all my work on them.? Cross performance, hyway, sterns or what. HLsupply is out of the total kits, does anyone else sell total rebuild kits with the tuneup included, at a good price? Or should I buy the stuff separate? Thanks for any help....


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## chainsawman2011 (Feb 19, 2017)

i have had the best luck with the cross kits they seem to hold up the best and come with caber rings 


Sent from my iPhone using Tapatalk


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## ginsenger (Feb 19, 2017)

chainsawman2011 said:


> i have had the best luck with the cross kits they seem to hold up the best and come with caber rings
> 
> 
> Sent from my iPhone using Tapatalk


so to do that I buy everything else seperate, ,, i don't know who makes the best stuff,,, quality for the money on the seals, bearings, gaskets filters, decompress valve and so on.
.


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## alexcagle (Feb 20, 2017)

Cross makes very good kits for both saws.
H.L. Supply has a good gasket set for both as well. Although I use a thin coating of yamabond 4 on the Stihl metal base gaskets, as I have seen them leak in the past.
I only use oem air filters on the Stihls. Same goes for decompression valves. I usually plug them, and use an elastostart with the black rope. The black rope is as durable as the husqvarna blue duraline. 
I highly discourage aftermaket air filters, as they simply do not filter anywhere close to oem. It's like comparing a Harbor freight tool to a Klein brand quality.
The TS420 tune-up kits are a good deal, if you can get an industrial dealer to sell them at a reasonable price.


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## ginsenger (Feb 21, 2017)

alexcagle said:


> Cross makes very good kits for both saws.
> H.L. Supply has a good gasket set for both as well. Although I use a thin coating of yamabond 4 on the Stihl metal base gaskets, as I have seen them leak in the past.
> I only use oem air filters on the Stihls. Same goes for decompression valves. I usually plug them, and use an elastostart with the black rope. The black rope is as durable as the husqvarna blue duraline.
> I highly discourage aftermaket air filters, as they simply do not filter anywhere close to oem. It's like comparing a Harbor freight tool to a Klein brand quality.
> The TS420 tune-up kits are a good deal, if you can get an industrial dealer to sell them at a reasonable price.


I have seen very few masons use the decompression valve, most just yank the cord till it breaks,,, lol,, plugging it might be the cheapest way to go.. wouldn't a leaky one make the saw run lean???


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## ginsenger (Feb 21, 2017)

chainsawman2011 said:


> i have had the best luck with the cross kits they seem to hold up the best and come with caber rings
> 
> 
> Sent from my iPhone using Tapatalk


Thanks, cross is what I was thinking from what I have been reading. I don't really know the little things to check on the finishes of the jugs yet, so that would cover me somewhat.
. For a few dollars more the claim to quality seemed to make sense to me.


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## ginsenger (Feb 21, 2017)

ginsenger said:


> I have seen very few masons use the decompression valve, most just yank the cord till it breaks,,, lol,, plugging it might be the cheapest way to go.. wouldn't a leaky one make the saw run lean???


searching on the internet one cant hardly get past the HL supply. the y are out of the kits,, after i spent many hrs searching and trying to make the right choice, dam,, back to the pc again.


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## ginsenger (Mar 20, 2017)

Husky K760 rebuild, New jug spark plug seat has pits that wont seal?? what to do?? I preasure tested with home made seals, Intake side wouldnt quite seal but pressure tested with soapy water around seals and gaskets while it had preasure in it ( although it would not hold pressure for required time) and found no other leaks. what should I do? try copper spark plug washer?, High temp gasket material or aerobic gasket eliminator?, pull the jug and lower the seat past the pits?, send the jug and kit Back?, it is a cross kit...


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## ginsenger (Mar 20, 2017)

I have idea for better block seal. just 2 flat plates for intake and exhaust with flat rubber and just clamp both at the same time with c- clamp or c-clamp vice grips. ought to work. 40 dollar for seal kit on ebay.


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## alexcagle (Mar 20, 2017)

ginsenger said:


> Husky K760 rebuild, New jug spark plug seat has pits that wont seal?? what to do?? I preasure tested with home made seals, Intake side wouldnt quite seal but pressure tested with soapy water around seals and gaskets while it had preasure in it ( although it would not hold pressure for required time) and found no other leaks. what should I do? try copper spark plug washer?, High temp gasket material or aerobic gasket eliminator?, pull the jug and lower the seat past the pits?, send the jug and kit Back?, it is a cross kit...


If the pits are real deep I'd send it back.
I put a little drop of oil on the threads of new spark plug. It aids in sealing in a new dry thread. A bit of red silicone in the pit first may help seal it too.
*
If you have a timesert spark plug insert kit, that would fix it, as it resurfaces the crush seal ring area with a cutter.
The kits are expensive, ($160), but worth it if you do 10 or so a year like I do. 
If you hang the saw upside down, it's possible to install an insert without removing the cylinder. You just have to be careful to get all the shavings out.
*
As to the intake seal problem; make sure that you are aware that there are two intake designs. Feb 2013 they changed the air intake area of the intake ports and corresponding flange. They are wider, and if an old flange is installed on a newer cylinder, it wil leak, and vice versa.
*
If you are having leak problems at the intake, make sure the bottom pivot flange isn't bent outward from somebody forcing it. It should be straight.
A light coating of WD40 on the face of the rubber sealing surface helps during assembly. If the surface is boogered up it needs to be replaced.
*
One thing about the K760 that is a pain,
is that you can't inspect the crankshaft bearings because of the skirts on the counterweights block visual access to the bearings. The seals have to be pulled in order to see the bearings condition.
A simple looseness test doesn't always cut it.
Be wary of a bent crankshaft if you find a bad crank bearing. The clutch is so close to the belt cover that it's quite easy for a dropped saw to get a bent crank. That and other tools being throw on top of them in a truck can cause this too.
It makes them wobble.
At 9,200 rpm it doesn't take long to damage bearings, or the crank bearing pockets.


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## alexcagle (Mar 20, 2017)

This flange off a dead saw works well for testing for me.
This one is for testing cylinders for leaks. I saw a bunch of aftermarket cylinders that would leak from the bore holes for installing the cylinder base bolts, that would gouge a hole into the transfer ports, causing a leak that is hard to see.


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## ginsenger (Mar 20, 2017)

Thanks,,,got dead stihl but not husky yet. but could use the rubber tubes off the saw I am working on. that would test the rubber tubes too as well as the intake seals. I can make the plates, just a matter of doing it. I got 2 more together last night, ready to test too. They are wanting me to hurry up. I been collecting the things I need to do a good slick job. need to learn the carbs and what to look for before the powerhead too.


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## ginsenger (Mar 20, 2017)

I use a very fine wet stone for sharpening knives and give the gasket surfaces a light decking. They are all pulled around the bolt holes. not much but a little. I stop decking just before All the color of old gasket is gone and then finish with scotch brite pad by hand.


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## alexcagle (Mar 20, 2017)

Yamabond-4 works great, if you re-use the TS420 cylinder base gasket. Thin coat, both sides. 
The aftermarket base gaskets aren't as good at sealing as the Oem ones. If the plastic coating is lifted you should replace it. 
Generally speaking, the crank seals don't leak unless a bearing is loose, or a bearing cage comes apart. If it is leaking, there should be a clump of dust & fuel around the leak like flies around a turd.
The only boot leaks I've seen were from boots being pulled from the aluminum flange from the factory, dropped/ran over, or somebody poked it with a screwdriver accidently. They are very durable.


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## alexcagle (Mar 20, 2017)

ginsenger said:


> I use a very fine wet stone for sharpening knives and give the gasket surfaces a light decking. They are all pulled around the bolt holes. not much but a little. I stop decking just before All the color of old gasket is gone and then finish with scotch brite pad by hand.


What gasket are you talking about? The base gasket is black.


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## ginsenger (Mar 20, 2017)

alexcagle said:


> What gasket are you talking about? The base gasket is black.


so far I totally rebuild them if they got low compression. the guys dont quit till the saw is dead and wont start, parts can be flapping in the breeze and as long as it will run they keep going., bearings, seals, jug and piston................ The jug gasket surface and case halves is what I was referring to. my Intake leak i mentioned was from a rubber gasket I trimmed to fit the intake flange and then worked a small hole in the impulse hole with a rattail jewelers file. Just used the exhaust muffler and another piece of 3/16th neoprene
rubber I have a bit of. the gaskets have sofar left some dark coloring on the mating parts jug match to block and both halves


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## ginsenger (Mar 20, 2017)

I did do have one that crank bearing are out, but on flywheel side... it burnt the crank cup too... another one piston came apart and damaged the cups from parts of the piston hitting it.


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## ginsenger (Mar 20, 2017)

I have seen them drop a saw from a six foot scaffold, got two that were either dropped from a good bit higher or ran over with the sky trac fork truck. broke ears of the blocks and squashed the fuel tank ect. was going to make 21 out of 2 as opposite sides of block was broke. I put them together and the block surface for the jug matches perfect. I have read to replace both halves together but I have seen each side sold seperat new.


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## ginsenger (Mar 20, 2017)

one out of the two, ,, i wish 21, lol


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## ginsenger (Mar 20, 2017)

The color I spoke of was not the gasket itself but what is there when old gasket is removed


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## ginsenger (Mar 20, 2017)

If they want me fixing these saws, on nights and weekends, after doing a youngs mans job all day, and me 60, (on days of working with 12 inch block most of them young guys are wore out), They are going to buy me new parts and tools to do a good job.. lol


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## alexcagle (Mar 21, 2017)

The carb seals diectly against the boots that are seated into the three bolt aluminum intake flange.
The intake gasket between the tank and carb is the only gasket.
They are in a new gasket set, even aftermarket sets.
*
If you reuse the crankcase gasket at the split, just push up slightly right before the gap closes tight. Then cut it off flat at the deck with a razor. If you do reuse them, you need sealer. They will leak with vibration between the longer stretch between the two bottom bolts. Something gasoline resistant like Yamabond 4, hondabond, 3bond. Silicone will leak. 
A minor case leak becomes more pronounced as the saw gets hot, and makes the saw lose power. 
*
Make sure you put a slight wedge between the crank counterweights when you pull the halves together with screws, so you don't bend the crank.
The bearing pockets and outer surface need to be oil free when put together or you'll see the bearing pockets waller out after a while. Lacquer thinner works great on a paper towel. A drop of green loctite "press fit" bearing retaining compound is a good idea too.


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## alexcagle (Mar 21, 2017)

ginsenger said:


> I use a very fine wet stone for sharpening knives and give the gasket surfaces a light decking. They are all pulled around the bolt holes. not much but a little. I stop decking just before All the color of old gasket is gone and then finish with scotch brite pad by hand.


There is only one bolt thread that doesn't have a dowel on the crankcase split on a TS420, and the cylinder base threads are in the cylinder itself..... what pulled threads are you referring to?


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## ginsenger (Mar 21, 2017)

The pulled boles are the ones in the block to pull down the head (jug) , and the block halves draw together bolts. actually so far I just have done the k760s. the place I ordered the bearings from gave me all one size so I just went to working on the huskies and haven't got back to the stihls yet. It is probably only a thousandth or so, maybe less, but they clean off first at the holes every time when I deck them. I pull the dowels out first. The stone is a super fine whetstone in new condition,it won't take off much very fast. but it covers me for the block having been hit or banged up or warped. I bought a set of these pullers in the photo and another set for putting the bearings in the case, to keep from hitting bearings or bending cranks as you say. I have a small lathe and made a seal driver, lol out a small aluminum flashlight that was already close to the right size. I already had pullers that it takes to get the bearings off the crank. I have a heat gun already. I had to weld the metric bolts on to 3/8th bolts to get the right length for the puller for the k760 with out spending on them too. I got metal to make the block splitter and got a templet from on here to make it for the stihls. But I am going to try to modify it to fasten each half the puller to a flat slotted snap-on puller bar. I would be adjustable to fit different widths then..I will have to get the blue loctite, all i got is red.. On the trucks and such I used to work on we went to the aerobic gasket eliminator instead of silicone. too much of the silicone goes inside and plugs up oil and water holes. I don't use it much. But I will check out the yamabond you suggest (thanks, I never heard of it before) . I try not to use old gaskets, the company got the money and I like to do a good clean job. but I haven't been throwing them away either.


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## ginsenger (Mar 21, 2017)

GREEN loctite I don't have either.


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## alexcagle (Mar 21, 2017)

Sounds like you're getting it figured out.
*
You might think about getting some extra long 5mm helicoils 2D and 3D to repair exhaust flange and cylinder base threads. Schinese make a good cheap 5m thru 22m helicoil kit on ebay for around$35- $40 that is great for repairing cutoff saws.


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## ginsenger (Mar 22, 2017)

I got the 5mm helicoil drill, tap, and install tool. got all kind of sizes for other stuff too. How long a thread insert should I get for the saws??? Fastenal had some different sizes but wish they had longer ones.......exhaust on stihl mostly and starter housings on the k760 so far.


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## ginsenger (Mar 22, 2017)

one of the stihls I did the exhaust on did not hold . I thought of using a tiny wire to put in the hole to help lock it down. I have done that on stripped holes in aluminum without a helicoil. but what do you know about it other than long helicoils. It is near imposiable to double them up as the threads wont line up and match. At least I haven't had much luck at that in the past on bigger stuff.


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## ginsenger (Mar 22, 2017)

Made this little piece to cap the exhaust on k760 tonight, some billet aluminum I had laying around, was just the right width got in a hurry and didnt centerpunch the boltholls so one is a tiny bit off. no big deal, just a few thousands. still got to get something rigged for the intake side.,,, How can I tell whats wrong if the block holds preasure.


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## alexcagle (Mar 22, 2017)

ginsenger said:


> Made this little piece to cap the exhaust on k760 tonight, some billet aluminum I had laying around, was just the right width got in a hurry and didnt centerpunch the boltholls so one is a tiny bit off. no big deal, just a few thousands. still got to get something rigged for the intake side.,,, How can I tell whats wrong if the block holds preasure.
> View attachment 566870


*
What exactly do you mean by the question in the last line?
*
These vacuum & pressure testing techniques may help.


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## alexcagle (Mar 22, 2017)

In reference to the muffler threads problems, here is an old thread I made on the issue.
*
http://www.arboristsite.com/community/threads/ts420-muffler-hack.299522/
*
The longer helicoils can be obtained on ebay by searching:
either 5m 2D helicoil
or 5m 3D helicoil
The 2d equates to length being 2 times the dimentional diameter. etc..


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## ginsenger (Mar 22, 2017)

What exactly do you mean by the question in the last line?I mean that I tore down several saws,that had burnt pistons without preasure testing them before I tore them down. Now after I totally rebuild them and if they pass a vac. and pressure test, What do I need to double check to make sure their right. If I give a saw back, they will run it into the ground before they quit. If it can be made to start and run they will make it go no mater what it does. I can't be there to keep an eye on each and every saw. So how or what do I do to make sure its right when done.


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## ginsenger (Mar 22, 2017)

alexcagle said:


> In reference to the muffler threads problems, here is an old thread I made on the issue.
> *
> http://www.arboristsite.com/community/threads/ts420-muffler-hack.299522/
> *
> ...


Thanks Alex


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## alexcagle (Mar 22, 2017)

Just recheck for leaks with soapy water to isolate a leak.
Things that can burn up a piston.....
Check tank vent operation.
Operator vest (clothing) sucking and blocking off cooling airflow on starter.
Partially clogged carb screen.
Restricted fuel filter.
Collapsing fuel pickup hose.
Water in fuel.
Diesel mixed with gasoline.
Boat 2-stroke oil.
Stale old fuel (detonation).
Low octane fuel.
Impulse hose pinhole.
Wrong heat spark plug.
Plugged cooling fins.
Intake leak.
Crank bearing seal leak.
Dirt or dust passing the air filter.
Incorrectly adjusted carburetor.(lean)


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## ginsenger (Mar 26, 2017)

Alex, my supposed leak under my home-made intake seal for testing the k760 was not the intake rubber, it was the jug gasket right under that. I found some hondabond 4, pulled the jug and put a thin sticky coating on each side. used green loctite on jug bolts.... It lost (1) pound of pressure in 5 or 10 min, I think that was from spark plug as I sprayed the soapy water on everything and all seemed good. It seemed to have sealed better after turning it in and out a bunch of times, and sitting a few days. I may still put a tiny bit of red hightemp on the spark plug seal before finishing.
??
I didn't put honda bond on crankcase half gasket. Should I leave it as is or what at this point??
??
Should I pull the crank case bolts one at a time and put loctite on them.??
?
If I take carb apart to check the screen should I use new gaskets or, put a kit in it,, Or is there a test to check all that without taking it apart.?


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## alexcagle (Mar 26, 2017)

That leak is acceptable. 
What about vacuum testing?
How did you put the crankcase together.
Heat, or long bolts to pull it together?
You don't need loctite on the spark plug, or the crankcase split gaskets.
You won't need to replace the carb gaskets, but you need to check for contamination, and put back together clean, then test it.


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## ginsenger (Mar 27, 2017)

alexcagle said:


> That leak is acceptable.
> What about vacuum testing?
> How did you put the crankcase together.
> Heat, or long bolts to pull it together?
> ...



I heated the housings and put the bearings, (froze bearings in freezer), pulled in with a threaded puller I bought for that and then used another threaded puller to pull the crank into the halves. used the modified flashlight to install the seals below the block surface. I forget now how many thousandths but I found the depth somewhere and made it as it was called for. when the outside of the driver hits the block the seal is maybe 4 mm below the surface.

The carb,,, I went ahead and took it off and used a new gasket....I used gas and a brush and air pressure to clean the whole carb at first then brake clean to clean inside, while holding the butterflies open, and then the whole thing again. 

A while back I fixed another one that the concrete dust had built up on the side of carbs so bad the butterflies wouldn't open up and wouldnt start. cleaned it and lubed the shafts and kept working it till it moved freely and they are still using it so far.


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## alexcagle (Mar 27, 2017)

I was taught that carb cleaners and compressed air are potential check valve killers. The caustic carb cleaner can distort the rubber disc, and high pressure can break the mylar ones. 
I was also taught the best flush and internal cleaner is a lubricant like WD40, as it is clean and it wets the tiny check valves.
I use lacquer thinner when finished on the carb's exterior to remove the oily residue to keep the dust from sticking to it.


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## alexcagle (Mar 27, 2017)

I'm a little unclear on what your seal depth should be, but it should be flush with with the case. If you drive them below deck too far it will eat up the bearing from contact.


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## ginsenger (Mar 27, 2017)

Replacing the seal on the flywheel side Mod. 500, 540Mod. 650, 700 Dismantle all parts on the flywheel side so that the seal is accessible. Remove the draw key for the flywheel by means of diagonal cutting pliers. Screw down the seal extractor as far as possible in the seal and pull off the seal. Lubricate the shaft with a few drops of oil and place a new seal in position with the shell plate facing outwards. Press down the seal with a suitable drift to the correct position in the crankcase, 1 mm (.04") below the crankcase plane. Fit the other parts in the reverse order to dismantling. 

this is from Partner_Workshop_manual.pdf


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## ginsenger (Mar 27, 2017)

there is a small bevel in the hole for the seal, it takes it down almost to the inner lower edge of the bevel. That's why I made the seal driver so it would stop at the 1mm below edge. With a driver that did NOT stop at the edge it would be near impossible to stop at a specific spot if the seal needed to be below the surface any at all. Hope I haven't screwed up on this..

I didnt blow directly in the holes of the carb but I should have held my finger on the fuel tubes on the outside. thanks though I will be even more careful in future.


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## ginsenger (Mar 27, 2017)

Replacing the seal on the clutch side Mod. 650, 700 In order to gain access to the seal the washer which lies inside the clutch drum must also be dismantled. This has a forced fit on the shaft and may be difficult to dismantle without being damaged. Use two screwdrivers first to bend out the washer far enough so that extractor 504 90 90-02 can be used. Dismantle the seal with an extractor 504 91 40-01. Fit the new seal by means of drift 502 50 82-01. Remove and install the seal ring in the same way as described for changing the seal ring on the flywheel side.
NOTE! Press the seal in the crankcase until the plate shell is flush with crankcase.

so I may have screwed up dag gone it. This is all the info I could find when I first started studying this. I have a newer shop service manual that didn't say anything other than use tool bla bla xxx


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## ginsenger (Mar 27, 2017)

You won't need to replace the carb gaskets, but you need to check for contamination, and put back together clean, then test it.
???
what do you mean here by test it. How do I test what??


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## alexcagle (Mar 27, 2017)

A carb test:
Pump it up to 8psi.
Bump the carb lightly in a wood surface. It should not lose pressure.
Then put your palm on the back of the carb while pulling light vacuum with your mouth. Then watch the gauge. Short drops should stop and hold without bleeding on down. That's not in any manual...... lol

The seal depth
Sounds good. 
It probably applies to any saw.

I got an early Partner K1200 behemoth in a tote with a new piston.


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## ginsenger (Mar 28, 2017)

alexcagle said:


> A carb test:
> Pump it up to 8psi.
> Bump the carb lightly in a wood surface. It should not lose pressure.
> Then put your palm on the back of the carb while pulling light vacuum with your mouth. Then watch the gauge. Short drops should stop and hold without bleeding on down. That's not in any manual...... lol
> ...



**
Where do I hook up on carb to pump up the 8 psi?
Do I pull the vacuum with my mouth at the same place?
**
What is your method of determining if a crankshaft is bent?
**
Is there an exact measurement or way to know without guessing if a rod bearings is worn too much?? 
As a beginner I can't quite tell. I know if it has up and down play, any is too much. but the slight side rocking is more than I know. I haven't the experience with a bran new one to judge by it. 
&
I really am grateful for your efforts to guide me. Art


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## alexcagle (Mar 30, 2017)

8 psi at the 45° inlet barb.

With it under 8 psi pressure, and holds, pull vacuum on either end of the carb throat with palm sealing off the other end.

A bent crank can be detected by rotating the flywheel, and observing the clutch pulley while held still from spinning.
A dial indicator works too.
The flywheel can be seen wobbling while rotating the clutch as well, or with a drill on the crankshaft, like on the youtube video below.


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## ginsenger (Mar 31, 2017)

alexcagle said:


> 8 psi at the 45° inlet barb.
> 
> With it under 8 psi pressure, and holds, pull vacuum on either end of the carb throat with palm sealing off the other end.
> 
> ...



Ok thanks. That won't work if the crank bearing is froze up. I guess if bearing is burned out and wont turn or anything that might have hurt the crank is found, after it is tore down, I should put it in the lathe and dial indicate it.
**
I used some green locktite on a bearing when installed. some must have gotten in the bearing and from the heat it setup and stuck. when it cooled down it was froze up. I got it freed but it still feels a little rough. What should I do???????????????? Never mind , I kept working it and wd40 and air, it finally cleaned up and turns smooth.


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## ginsenger (Apr 1, 2017)

Alex I have two stihls ts420 that have broken blocks. Broken on opposite halves. im looking at using half from each saw and making a one out of the 2. ,,What do you think of that?,,, they were fairly new.
What should I look for as far as if to use one of the pistons and jugs over with new rings?? Or should I just buy a new piston and rings and use one of the jugs over??


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## ginsenger (Apr 1, 2017)

I did a carb test. This is on a husky k760...8psi on inlet taped it on wood and the pressure dropped a little every time I tapped it??
when I did a palm test it dropped all the way.
** I did pressure test by a pdf service manual and it pumped up only to 18 psi and fell to 14psi. the other pressure tests seemed ok as best I could tell.
this saw is fresh built, it seemed to wallow just a little on a rev. Another one I just did revved better, smother right on up to top rpm. It just sounded better with more pep than this one.. that is why I pulled carb back off this one.


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## alexcagle (Apr 1, 2017)

The green only needs to be like two drops, and spread around the pocket.
I use it only on the TS420 because of the plastic rings not liking heat.
When I use long bolts to draw a crankcase together it lubricates too. - But make sure to lightly wedge something centered between the counter weights of the crank first, so it won't stress the point at which the crankshaft was heated and joined together at the factory.
*
Service manuals on the K760 carb say to have the lever just below the deck, but if the diaphragm is malformed slightly, or moves at an angle, it can cause it to leak when it when it's bumped. I usually have the fulcrum contact point set a little lower if it leaks when bumped.
At 8psi, pulling slight vacuum, try to make it drop 3psi and stop.
It should hold with no bleeddown after the three psi drop.
If it bleeds on down, either the diaphragm needs replaced, the needle spring is weak or incorrect.
If it fails this test, try removing the diaphragm and cover, and pump it up to 8psi, the lightly touch the fulcrum an see if it stops positive. If it does, then the diaphragm's center round aluminum contact may be wrong in thickness to work correctly. A carb kit must have a mated fulcrum and the center contact of the diaphragm design to work in the carburetor it was designed for.
Like these Tillotson and Walbro versions.


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## alexcagle (Apr 3, 2017)

The best settings I've found on the K760 is just shy of 1-1/2 turns out on both high and low needles.
These saws have a rev limiter on the coil. That's why they miss at wot when under "no load" conditions.
At idle they normally sound like a cammed out race car.


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## ginsenger (Apr 8, 2017)

alexcagle said:


> The best settings I've found on the K760 is just shy of 1-1/2 turns out on both high and low needles.
> These saws have a rev limiter on the coil. That's why they miss at wot when under "no load" conditions.
> At idle they normally sound like a cammed out race car.


**
I took another carb from another saw , it passed the test, and used it. The benefits of them all belonging to the same person. I think I will get a kit and learn a little from putting it in while not feeling as much rush.. They needed saws now. I been slow trying to learn instead of saying I know it all and slamming them together and not knowing ****. So far i have done 4, One ( the first one) had a crank bearing go back out after 3 days. It shattered when I tried to pull it. I sold them a new crank. The rest of them have been running for a week or two and are doing good. Still got 4 in the floor. All of the first ones were leaking under the jug at the crankcase split when I checked them for leaks.. The hondabond 4 took care of that. The 328 EZ-tach+plus I got for rpms does not seem to do good for checking max rpm. It makes for a question rather than a sure thing.


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## alexcagle (Apr 8, 2017)

The max rpm is limited, so there really isn't any reason to check them with a tach. 
I use them on chainsaws, and to set idle speed & mix on TS420's that tune by setting highest lean dropoff at 3100 rpm, then bringing it back down to 2800 rpm with the "L" mixture screw.


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## ginsenger (Apr 8, 2017)

alexcagle said:


> The max rpm is limited, so there really isn't any reason to check them with a tach.
> I use them on chainsaws, and to set idle speed & mix on TS420's that tune by setting highest lean dropoff at 3100 rpm, then bringing it back down to 2800 rpm with the "L" mixture screw.


**
If you reuse a jug, what do you cleanup, shine, the bore with?? using same piston with new rings


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## alexcagle (Apr 8, 2017)

I use a small knot cup on a dril to clean out the carbon on the cylinder ceiling, and a Dremel rounded end cutter to clean the carbon out of exhaust port. This can occasionally can rough up the edges at the exhaust port.,
Then take a 502 or 503 Dremel flap wheel to remove any aluminum scoring transfer, and smooth out any roughness at the exhaust port edges, from the carbon removal step.
If you run your index finger around the cylinder wall, you'll feel any roughness that could scratch the piston.
Due to the accelerated wear of masonry dust, and how hard it can be to clean the
carbon out of the ring grooves, I would recommend always using a new piston kit. The reason for this is the ring grooves get excess clearance, which lets the rings move up and down too much, and can cause problems with rings breaking and ring locator pins that getting worn and letting the rings rotate and hang on a port.
Not to mention the ring ends wear a step in the sealing surface of the ring lands that may not seal well with new rings.
*
Stratified charge cylinder designs are not as susceptible to excessive intake skirt clearances causing "spitback" through the carburetor.
On conventionally designed piston ported engines, like the TS400, this "spit back" spray soaks the air filter, causing flooding conditions. If the machining marks are completely worn smooth on the piston intake skirt, or the bottom edge is shiny and rounded, then piston replacement is warranted.


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## ginsenger (Apr 11, 2017)

What is the flywheel and clutch torque for stihl ts420?


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## alexcagle (Apr 11, 2017)

ginsenger said:


> What is the flywheel and clutch torque for stihl ts420?


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## ginsenger (Apr 11, 2017)

alexcagle said:


> View attachment 572214


what is the clutch ( the cast piece with the springs? or what are they calling it? iS IT THE DRIVER?


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## alexcagle (Apr 11, 2017)

Yes. 
Strange that they call it that.


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## ginsenger (Apr 11, 2017)

alexcagle said:


> Yes.
> Strange that they call it that.


 tHANKS A BUNCH


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## ginsenger (Apr 11, 2017)

Well I just built a Johnny Cash one, or a heinz 57. I took the best of 3, it seems to have good compression. piston and jug came from one that had been ran over it looked like. they wanted another saw tomorrow and I dont have enough new parts. It may last a day or maybe if lucky a year. lol


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## ginsenger (Apr 19, 2017)

Do you have any k760 flywheels for sale,, cheap lol.


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## ginsenger (Apr 19, 2017)

I have a k760 that leaked from under the crossover tubes or plates on the side of the jug. I pulled them and used honda bond. one of the tiny rubbers gaskets broke so I robbed one off a junk jug and used it with more honda bond as well. tested them this morning and the hold pressure now. do you think it will hold up under use?


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## belgian (Jan 11, 2022)

Good Info in this thread and I would really like to offer a beer to Alex for his generous input, if only he was on this side of the ocean. This guy knows his stuff !!

Against experience with stone cutters, I took on another rebuilt project for a Husqvarna K750 (same as partner). What started as a good cleaning project with possible new ring set, turned out to a complete rebuilt with new piston, crank bearings and seals, disc bearings, etc. These machines take a lot of dirt and any well used machine does need a complete overhaul, which means a lot of work and $$$$.

I found that this machine has a (unknown to me ) friction retarder on the disc driving pulley, which I have never noticed on any newer model. What is its function and should I get rid of it ? it seems still complete.


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