Old Stihl 025. Cranks but won't run.

[BlackOps]

i have another brand saw but 2 weeks ago started and full run stalled. many times. tried everything. took it in and the guy said coil was gone. he is waiting for the part. that is all he said. the new kid is very unfriendly unlike the old owner who retired2 yrs ago. guy seems to not have parts or take forecer to get anything. just an off comment. so maybe that could be the issue with your saw.

might be so far off i sound ridiculous. but the symptoms seem very similar.

 

[N80]

@5030 Tank strainer replaced already. Only thing left in the fuel system to replace is the impulse tube.

 

[N80]

@BlackOps Could be the magneto. They're not expensive but if I keep replacing things I could have just used the money to buy a new saw. I'm already in about $80.

 

[BlackOps]

i understand. i have had to make that call 2-3x in my 70 yrs. better to buy a new and start again. i was just explaining what i am going through now. sounded similar to your experience.

 

[Ford850]

You might have done these, but they are the most common causes for your symptoms:
Check the muffler to be sure it isn't plugged.
Replace the impulse line as suggested earlier. (plenty of articles and videos online showing how to do this)

 

[dodge man]

I posted a pic earlier of the tube that connects the carb to the engine. It also shows the impulse tube. They just slide on but are probably on pretty tight. I reused mine on my rebuild. Get a new spark plug, I had one go bad once, but that’s probably not the problem. I’d say it’s the ignition module or a air leak.

 

[5030]

@5030 Tank strainer replaced already. Only thing left in the fuel system to replace is the impulse tube.

Think I'd do that (replace it) Don't take much in the way of a compromised impulse tube to starve that tiny diaphragm in the carb and keep it from pulsing. No pulse equals no fuel.

 

[N80]

I will replace the impulse tube. It is not hard to do but requires another tear down because it isn't very accessible. No big deal. New spark plug too.

Muffler is clear.

Couple of thoughts: When it cranks it cranks easily and runs normally for 10-15 seconds then stops as if flooded (has to sit for a while and then will restart). Pull the plug and it is wet. So it doesn't seem to me it is spark or fuel that is the problem.

So now I'm wondering if it is an internal issue. From the exhaust port the piston side and rings look great. But, maybe it is scored where I can't see it, or cracked or a hole burned in the cylinder?

Anyway, new impulse tube and new spark plug and then it goes to my nephew if still a no-go.

 

[BlackOps]

and then he'll have a saw that is no good too. heh heh

 

[N80]

He’s a bit of a wiz with saws. He rebuilds them and modifies them. So if there is an internal issue he’d find it.