Stihl 036 WOES

[Poleman]

Need some ideas guys. I'm working on an older 036 that is in great shape and hasn't been abused. I scoped the cylinder and it's perfectly clean on bother sides. 160lb Complete @4k feet.

ISSUE: Saw starts and runs fine...the problem is wot.....tach set to 12,8 which it goes to then about 2 seconds in it jumps to 15,5+, kinda like a 4bbr opens up.

I've replaced crank seats and saw hole 8lb pressure and vacation. Replaced the intake boot, impulse line, carb kit and fuel line.
I've tried a different carb and coil and it still does the same thing.
Fuel system checks out as it should. Carb seems good. About the only thing I haven't done is pull the cylinder.

Any ideas I haven't tryed.......yet??????

 

[Canadian farm boy]

Fuel line collapsing or kinked?
Fuel filter?
Carb not sealed %100 at the intake manifold flange?
Intake manifold not sealed %100 at the cylinder?

 

[Poleman]

Fuel line is new oem with new filter.
Intake boot is new....but seemed slightly long. I double checked the set on the cylinder and it's where it should be. When I say long it sticks out above the metal collar on the air box.

 

[Lootbug]

Does it have a decomp? Not likely, but perhaps a fault there if it has one.

 

[Poleman]

Nope, no decomp....don't have to worry about that!!! Lol

 

[David Young]

Most likely you have a problem with the meter diaphragm.

You words basically

It is tuned right but runs out of fuel.

So what causes that?

 

[Lootbug]

Hmm seems like you've covered all the bases. Tank vent? Just throwing out random stuff lol.

 

[Chainsaw Jim]

Hmm seems like you've covered all the bases. Tank vent? Just throwing out random stuff lol.

I was about to say that myself. If the boot was leaking then it would likey be hard to find a good tune for the low side.

 

[Four Paws]

I have had a saw act the same way, it turned out to be a bad carb.

I would swap a known good carburetor on that saw and go from there.

If the carb cures the issue, then you can tear into the original carburetor and attempt to fix it!

 

[Poleman]

No not vent, it's the old plastic style with the screw inside...checked that.

It holds tune but just at wot when the rpm's jump.
New carb it did the same.

I've had original carb apart a dozen time....lol. resealed the Welch plug, played with the needle arm setting....checked and double checked....

 

[Carbine]

You have a piece of debris, or paint peel from the crankcase, blocked in the impulse nipple coming out of the crankcase. Report back and let me know .
That is of course, if you have ruled out a bad carb (which sounds like it is, even if you have replaced it.)

 

[Four Paws]

Bust out the mityvac and check it for an air leak...it's plausible.

 

[Poleman]

That's what I thought it was the carb but it was the same with a new one. Really thinking of removing the cylinder to see if there is something funky I can't see with she scope. Like a fleck of paint or debris on the impulse opening but I don't think that would cause the jump in rpm's at wot like it's doing.

 

[Poleman]

I've checked pressure and vac.......will hold 8lb indefinatly.......

 

[RI Chevy]

Maybe a small crack in the case? Fellow member dall is really good with 036/360's.

@dall

 

[Carbine]

That's what I thought it was the carb but it was the same with a new one. Really thinking of removing the cylinder to see if there is something funky I can't see with she scope. Like a fleck of paint or debris on the impulse opening but I don't think that would cause the jump in rpm's at wot like it's doing.

I've had one do this, and it was a partially blocked impulse hole on inside of crankcase. Not saying yours is, but I would definitely shine a flashlight down nipple to see..

 

[dall]

could the flywheel be loose or coil going bad ? youve covered the basics and more

 

[dall]

i know poleman is good on carbs and fuel delivery and why i think it is spark related

 

[RI Chevy]

Maybe a short somewhere in the plug wire? Or in the on/off switch? Electrical?

 

[dall]

i had a guy bring me a jonesred said it would idle good but no power turned out the cap on the plug was missing and the spark had to jump across from spring to the tip new plug fixed that one