"Stumped" by an 044

[Edge & Engine]

I have an 044 on the bench that is giving me nightmares. I've thrown every trick in the bag at it, and since I'm not making any headway I figured I'd throw it up here in hopes of some ideas.

Problem: Saw idles for <5 seconds then starts to speed up (leans out) until it dies. Classic symptom of an air leak, I've seen it hundreds of times.

What I've done so far:
I pressure and vac tested the crankcase, blocking off at the carburetor end of the intake boot in order to rule out a boot leak. The first time I did this, I found a fast leak at the cylinder base gasket. I checked the squish and found there to be plenty to delete the gasket, which I did and used Permatex Copper. This solved the leak, but did not solve the problem. I have done pressure/vac tests 3 times since then and there is NO air leaking whatsoever. I've removed the impulse tube and pressure tested it. I replaced the fuel line & fuel filter. All this did not solve the problem so I figured it must be the carburetor (which I had already cleaned & rebuilt), so I ordered in a new carburetor, but it still does the exact same thing. I even replaced the clutch side crank seal just for kicks (didn't replace the mag side since it goes bad less commonly, but I did check it and there are no signs of leakage). No visible play on the crankshaft bearings. What am I missing here? I didn't try a new coil because it just doesn't seem to be an ignition problem, but maybe I should just to try? I'm truly at my wit's end! -Kyle

 

[Old Longhair]

Can you get any kind of read from the plug? Have you pulled it immediately to see if it indicates a carb issue?
I'd try the coil too. They can do some funny things.

 

[Trx250r180]

Do you have a pic of the clutch side bearing ? if it is not in all the way will act like this ,when it is not running will pass leak test ,but when running it leaks ,a smack with a socket and hammer usually sets it back against the crank and the leak goes away and can adjust the carb ,may not be the problem ,but i have had a couple saws do this .

Also if the fuel line gets soft could be sucking itself closed ?

Edit ,a little hole in the fuel line will act like this too

 

[blsnelling]

Can you get any kind of read from the plug? Have you pulled it immediately to see if it indicates a carb issue?
I'd try the coil too. They can do some funny things.

You can't get a plug reading from a engine that's idling

 

[lone wolf]

Anyone catch that he used "permatex copper " for the cyl base seal? Go back and test it for leaks one more time only now rock the crank snouts on the left and right sides while holding vac and see if it drops due to a bearing moving.

 

[mdavlee]

Anyone catch that he used "permatex copper " for the cyl base seal?

It works. I've used it a long time back.

 

[lone wolf]

It works. I've used it a long time back.

I thought it was silicone based?

 

[Trx250r180]

I thought it was silicone based?

I have black permatex under bases of 2 saws ,no leaks ,as long as it is fuel or oil resistant should be ok .

 

[lone wolf]

It works. I've used it a long time back.

I thought it was silicone based?

 

[mdavlee]

The problem could be coil related or the impulse isn't strong.

 

[lone wolf]

The problem could be coil related or the impulse isn't strong.

Do you check impulse with a vac gauge to see it move ? What about the seals leaking when running as in loose crank bearings?

 

[mdavlee]

Usually check the barb for a clump of sawdust in it or something like that stopping it up.

 

[lone wolf]

Op, how about you check the seals with vac holding and wiggle the left and rt crank ends to see if it leaks like that?

 

[albert]

I thought it was silicone based?

Have you ever split a case on saws that do not use a gasket from the factory, like poulan 3400 series?

 

[lone wolf]

Have you ever split a case on saws that do not use a gasket from the factory, like poulan 3400 series?

Lots of motorcycles.

 

[albert]

• The sleeve on the clutch side of the crankshaft that the inner lip rides on can leak between the od. of the crank and id. of the sleeve. May only leak when running. You can use heavy grease where it seats against the bearing and crank. Check the entire pulse circuit and decomp valve if applicable.

 

[albert]

Lots of motorcycles.

These saws used black rtv from the factory.

 

[Deets066]

Op, how about you check the seals with vac holding and wiggle the left and rt crank ends to see if it leaks like that?

Or you can spray Wd-40 at the seals while running, if it revs up then you know it's leaking by. This would be difficult to do since the saw leans out and dies in 5 sec though.

 

[huskihl]

Is it filled with fuel?

 

[Edge & Engine]

Yes it has plenty of fuel, and a new fuel line plus I had pressure tested the old fuel line, it was holding pressure but was kinda spongy so I replaced it anyways. I think what I'll do next is as some have suggested, rock the crank while under a vac/pressure test and see if I get any leakage. I haven't put a gauge on the impulse line, but that's a good idea. I've already sprayed carb cleaner at the base gasket and intake boot, impulse connections to check for leaks there. The only seal I would be able to do this on would be the clutch seal since you can' run the saw without a flywheel.
I've used copper permatex for years without problem:
http://www.permatex.com/products-2/...-temperature-rtv-silicone-gasket-maker-detail

And BTW, it is possible to keep the saw running for any length of time by constantly adjusting the carb or playing with the choke. That's why I'm quite confident it's some type of fuel mixture related problem.