My new/old Stihl 044

[RiverRat2]

Just looking at the carbon in your close ups, Great photos BTW

Thanks RR...

When I get the basic maintenance items done, will it do any more harm than already done to just go ahead and run it?

Probably would not run it much,,, piston has seen better days,,,, but if it was mine I would try to decarbonize it some how,,,, if money is an issue you can poor boy it as below,,, and it will do fine for a while,,,if ya got a few bucks you can spend go buy an OEM piston kit!!!! Curt bailey maybe,,, may find one on fleabay,,Cheapstihlparts,,,etc,,, clean the Jug as below,,, light hone and slap it back together!!!!!!! Yahooo-buckeroo!!!!

If you are ok with pulling the jug, I'd snatch it off and de-carbonize it,,,get a new set of rings,,,at least,, clean the ring grooves, (break one of the old rings and use it to gently clean them with some solvent like var-sol,) the top of the piston, jug exhaust port, inspect all,,, take some fine crocus cloth or Emory paper and lightly buff the areas below the bottom ring on the piston skirt HORIZONTALLY!!!! Some use a bead blaster if you have access,,,helps a slightly worn piston by the ser. # id say it is around 8-9 years old but is a 12mm wrist pin model so that is good,, check the big end bearing for vertical end play, should be none,,,probably isnt any,,,, as good as you say it runs,,,

If you are not ok with pulling the topend I've heard Stihl makes a decarbonizer but I think it is intended for the fourmix moto's not sure,,, if you can use it on a pure two stroke,,, some guys here have posted about SEAFOAM???? I think with good results but that wont help your piston wear

River

 

[sperho]

I'm going to go ahead and pull the top end off. I don't need this saw right now, so I can spread the time and cost out quite a bit. I want a strong runner when I'm finished as it seems to perfectly complement my 260 and if I can do the whole job for under $200, all the better. I'll be asking more questions, don't worry. Now, just need to get the service manual from the man with the plan...

 

[sperho]

OK, so people have recommended that I determine why the piston failed so that I may correct the problem before it happens again after a rebuild. After reading a bunch of other threads today, I'm gather that I need to do a leak and/or vacuum test to see if there is an air leak somewhere? Am I inferring correctly? Is there anything else that I should do to attempt to track down what happened? Bad gas seems like it would be the only thing left at the end of the process should nothing else pop up, but I don't know what the process entails exactly.:monkey:

 

[Lakeside53]

You got it... Pres/vac test, and carb...

 

[RiverRat2]

post,,,,search

OK, so people have recommended that I determine why the piston failed so that I may correct the problem before it happens again after a rebuild. After reading a bunch of other threads today, I'm gather that I need to do a leak and/or vacuum test to see if there is an air leak somewhere? Am I inferring correctly? Is there anything else that I should do to attempt to track down what happened? Bad gas seems like it would be the only thing left at the end of the process should nothing else pop up, but I don't know what the process entails exactly.:monkey:

Ya know it seems funny to me,,,,,If it idles smoothly and you can stop it in the middle of a cut and it dosen't die and then power back into a cut,,,,I'm almost bettin you dont have a vacum or pressure leak,,,could be a lean carb problem,,,, could be its just worn out!!!!!!


I've gone over it in detail on a pevoius thread a few weeks back,,,who's saw was it fellas!!!!! their right though Before you tear it down,,,,ya need to check it,,,

to tired to re type it all tonight pehaps someone can find the thread and post a link to it,,,, goes into good enough detail for you to get it done very cheaply ya back off on the muffler flange screws a and slide the muffler out,,,,put a rubber strip,,,wedge,,,behind the muffler push it in till the flat rubber meets inside of muffler screws blocking the exh. port;;; tighten screws against rubber strip....do same to carb,,,,slide out on studs rubber strip again,,,, when you retighten carb,,,, push impulse hose to the side so it doesnt get carb line back in cause thats where your gonna hook the pump and vac tester,,,,,,,,,,,,,,,,,pressure should hold for at least 20 sec .7 bar or about 8 psi,,,,, vac...4 bar or 5 psi for same time but longer is better on both test!!!!!! (Andy are you Out there running in Stealth Mode???)

 

[sperho]

Ya know it seems funny to me,,,,,If it idles smoothly and you can stop it in the middle of a cut and it dosen't die and then power back into a cut,,,,I'm almost bettin you dont have a vacum or pressure leak,,,could be a lean carb problem,,,, could be its just worn out!!!!!!

If it doesn't cost much, I'm going to put whatever is in a carb kit into it just to be safe. It's an HD17 carb.

I've gone over it in detail on a pevoius thread a few weeks back,,,who's saw was it fellas!!!!! their right though Before you tear it down,,,,ya need to check it,,,

Is this the thread you are referring to? I read that one with interest...

pressure should hold for at least 20 sec .7 bar or about 8 psi,,,,, vac...4 bar or 5 psi for same time but longer is better!!!!!!

Good to know. I have a Mity Vac that does vac and pressure, but there is no gauge on the pressure side - I'll have to find one somewhere...

I have everything around the head removed and man, this saw is dirty. I'll do a pressure/vac test before removing the jug...

 

[Lakeside53]

Longer is better. On a rebuild it should hold indefinately. The "20 second" rule is more for problem determination on an old saw.

 

[RiverRat2]

Do I hear an echo?????

Longer is better. On a rebuild it should hold indefinately. The "20 second" rule is more for problem determination on an old saw.

Yes Longer is Always Better!!!!!!!!!!!! but thats what we are trying to determine,,,,, He hasn't rebuilt it Yet!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Sperho,,,,, yes that is the thread!!!!!!!!!!!!!

G'day mates,,,,,,,

 

[RiverRat2]

Is this the thread you are referring to?
I read that one with interest...

Good to know. I have a Mity Vac that does vac and pressure, but there is no gauge on the pressure side - I'll have to find one somewhere...
I have everything around the head removed and man, this saw is dirty. I'll do a pressure/vac test before removing the jug...

Good plan if you are rebuilding the topend always good to kit the carb even if it was running OK as You say,,,,,

I aways have a spray bottle with soapy water to find leaks,,,, And if ya dont find any while ya still have it sealed for the pressure test before you tear it apart take the recoil off so you can clean in there and behind the flywheel and inside of recoil too,,,,, get some purple cleaner,,, mixed 3 parts water 1 cleaner,,,,, soak the moto down good let it set about 5-10 minutes then blast it with water,,, hot water works best,,, get all up in around the handle mounts too

You will be amazed how well that stuff works,,, nothing like having the moto all clean before teardown,,,,,,,,,,,,,

 

[Dadatwins]

If you are going to pull the head and rebuild the carb, I would suggest getting a new carb boot while you have it apart. If the saw is that beat and dirty it will probably need one.

 

[sperho]

If you are going to pull the head and rebuild the carb, I would suggest getting a new carb boot while you have it apart. If the saw is that beat and dirty it will probably need one.

Will do.

 

[sperho]

OK. With the intake and exhaust blocked off with inner tubes, plug installed, and a MityVac connected to the impulse line, I pulled a 15 inch Hg vacuum while the piston was at TDC. After 5 minutes, no change in vacuum. Then I slowly rotated the flywheel for about 3 minutes and was able to reduce vacuum by ~0.5 inches, or 3%. I'm inclined to not mess with any seals. Opinions?

I don't know how to test a carb yet because I don't have a service manual and I've not been able to locate a thread that tells me enough information on how to do it. At this point, I'm blaming the piston's condition on either a leaky carb (to be tested when I know how) or more likely, bad and/or incorrectly mixed gas. Any other reasonable possibilities? Anything else I should test before pulling the cylinder?

 

[SawBum]

OK. With the intake and exhaust blocked off with inner tubes, plug installed, and a MityVac connected to the impulse line, I pulled a 15 inch Hg vacuum while the piston was at TDC. After 5 minutes, no change in vacuum. Then I slowly rotated the flywheel for about 3 minutes and was able to reduce vacuum by ~0.5 inches, or 3%. I'm inclined to not mess with any seals. Opinions?

I don't know how to test a carb yet because I don't have a service manual and I've not been able to locate a thread that tells me enough information on how to do it. At this point, I'm blaming the piston's condition on either a leaky carb (to be tested when I know how) or more likely, bad and/or incorrectly mixed gas. Any other reasonable possibilities? Anything else I should test before pulling the cylinder?

Everyone is giving you great info. Your piston issue is pretty simple. Rings started sticking due to old or over mixed fuel, the scarring on the piston and rings is from carbon breaking off the exhaust port (I hope it didnt affect your cylinder but very possible) This fairly common in older saws. Even simple ring wear can cause this. dark piston skirt is caused from combustion flashing past the rings. Your vac/pressure test seems perfect. I think you only have a top end issue and a real good carb clean. The only tests you can run on the carb is a pressure leakdown on the inlet needle and a high speed ck valve test. If the saw is running as described in the begining, your high speed ck valve should be fine, just need to ck for bleed down of your inlet needle, attach your pressure tester to the intake nipple on your carb and pump it to 7/10 bars, if it holds great, but please rebuild the carb anyway and recheck the inlet needle. Great buy on a great saw. I hope I helped and didnt repeat what others have told you.

 

[sperho]

Everyone is giving you great info. Your piston issue is pretty simple. Rings started sticking due to old or over mixed fuel, the scarring on the piston and rings is from carbon breaking off the exhaust port (I hope it didnt affect your cylinder but very possible) This fairly common in older saws. Even simple ring wear can cause this. dark piston skirt is caused from combustion flashing past the rings. Your vac/pressure test seems perfect. I think you only have a top end issue and a real good carb clean. The only tests you can run on the carb is a pressure leakdown on the inlet needle and a high speed ck valve test. If the saw is running as described in the begining, your high speed ck valve should be fine, just need to ck for bleed down of your inlet needle, attach your pressure tester to the intake nipple on your carb and pump it to 7/10 bars, if it holds great, but please rebuild the carb anyway and recheck the inlet needle. Great buy on a great saw. I hope I helped and didnt repeat what others have told you.

Thanks for the words - it's good to hear others' with way more experience than I stab at what went on with this engine.

By 7/10 bar, do you mean 0.7 bar, i.e. ~10 psi? I can do this with the carb on the bench and not the saw? Seems easy enough...

 

[RiverRat2]

your test proved tge intake boot is fine as well,,,

OK. With the intake and exhaust blocked off with inner tubes, plug installed, and a MityVac connected to the impulse line, I pulled a 15 inch Hg vacuum while the piston was at TDC. After 5 minutes, no change in vacuum. Then I slowly rotated the flywheel for about 3 minutes and was able to reduce vacuum by ~0.5 inches, or 3%. I'm inclined to not mess with any seals. Opinions?

I don't know how to test a carb yet because I don't have a service manual and I've not been able to locate a thread that tells me enough information on how to do it. At this point, I'm blaming the piston's condition on either a leaky carb (to be tested when I know how) or more likely, bad and/or incorrectly mixed gas. Any other reasonable possibilities? Anything else I should test before pulling the cylinder?

I would be inclined to agree with Sawbums idea of the carbon flaking possibility or something along that line (did it suck back to injest the flaking carbon???ha ha,,,),,,People buy cheap fuel (regular) and walmart oil and do dumb things,,,, the way you describe it ran,,,, I'm thinking your carbs internal checkvalves are ok and a good kit and cleaning will probably have you all set just dont blast the internal passages with high pressure air,,,,,,,, FYI excellent results on the vac test,BTW,,, as said prior hook the pressure tester to the fuel inlet line and the carb should hold pressure at about 12-15 lb actually a good test is remove your test rubbers out the carb back on pull the fuel filter and hook the pressure tester on the fuelhose this checks your fuel hose and carb inlet valve @ the same time,,, same test pressure as above,,,,,

 

[sperho]

I should have known that one day that I would own a saw that had a case of suckback. Suckback sucks back.

 

[Dadatwins]

Good test, the deal on the saw is getting better. The test shows the intake boot is good and holding pressure, but I would check it anyway. It might have been changed when the new tank was installed. If it feels soft or looks like is is original I would change it. cheap insurance. Check the rubber pulse line also while it is apart same inspection. Easier to change these now for a few dollars while you have the saw apart. The only other rubber item is the fuel line and that usually comes new with a new tank, so that should be ok but check it anyway especially if bad fuel/mix looks like the problem with this saw. Look at the end where it connects to the carb,and where it passes into the tank if it looks soft, cracked, change it. Again all these are working based on the pressure test, but it is cheap insurance to replace and easy while the saw is apart.

 

[sperho]

Carb + fuel line tested at 6 psi, no delta after 10 minutes. Does it make sense to rebuild it?? Not to be lazy or anything, but if it ain't broke*, is it worth fixing?

Got ready to pull the cylinder and come to find out that my BR420 scrench with the T-27 end on it will not fit through the fin holes on the jug to be able to access the bolts that hold the jug on. I thought there was a 24 hour Advance Auto nearby, but alas, they changed their hours back to closing at 9. I was really hoping to see the condition of the cylinder tonight. Oh well...tomorrow is another day.


*Given that it idled well and pulled well and it pressure tested well, that is...

 

[Lakeside53]

On the carb all you tested with pressure is the inlet valve. I'd check the inlet screen AND the metering diaphragm (make sure it's "supple")...

 

[sperho]

I may as well share what I came up with for a intake port block-off contraption. Rubber from a bicycle inner tube was the diaphragm material and the hold-down plate was a 1/2" chunk of plastic. Much easier to work by hand than aluminum or steel and readily available to me (I work for a company that makes plastics and this was a sample of material). A rat tail file was used to make a few notches in the rectangular plate so that it would slip between the carb bolts and the plate's over-sized width would cover the whole boot and make a good seal. A few light fixture threaded tubes as stand-offs and the stock nuts to clamp it down.