Is This The Symptom of Shaky Manifold Stihl 021?

[hotajax]

Saw starts OK, and has great throttle response. New Plug, air filter, and fuel line. But put it down, it revs up and down like it's looking for a sweet spot to idle at.

Possibly an impulse line? I dunno, I just break 'em. Any ideas are greatly appreciated

 

[altatim]

Impulse line, fuel line, and intake boot would be what I would check in that order based on your symptoms. All available at Stihl and relatively cheap. Don't forget if you replace a fuel line do the filter too!

 

[pioneerguy600]

Crank seals just starting to leak, not totally gone yet can cause those symptoms Check the saw with a vac and pressure test, rotate the crank while doing the test, check the crank for any up and down movement.

 

[stihltech]

Again- magic wand out of order.
You need a pressure and vacuum test.
Alternative- take your favorite brand of Brake cleaner (with a straw on the nozzle). While idling-Spray in between the cylinder and carburetor housing. You just checked the intake, pulse line, and cylinder sealing on that side. Spray underneath the muffler. You just checked the cylinder seal on that side. Try to spray behind flywheel and behind clutch. Very hard to do, but it can be don. You just checked crank seals.
Follow all other suggestions.
You can diagnose or you can guess. Do not have that luxury in a shop.

 

[altatim]

You can diagnose or you can guess. Do not have that luxury in a shop.

Sometimes its easy to forget what time is worth lol.

 

[Hman1024]

Again- magic wand out of order.
You need a pressure and vacuum test.
Alternative- take your favorite brand of Brake cleaner (with a straw on the nozzle). While idling-Spray in between the cylinder and carburetor housing. You just checked the intake, pulse line, and cylinder sealing on that side. Spray underneath the muffler. You just checked the cylinder seal on that side. Try to spray behind flywheel and behind clutch. Very hard to do, but it can be don. You just checked crank seals.
Follow all other suggestions.
You can diagnose or you can guess. Do not have that luxury in a shop.

When using this alternative method, brake cleaner would cause a stall or decrease in rpm? Just wanted to know what to expect.

 

[stihltech]

Usually a stumble or stall.