Old Stihl 025. Cranks but won't run.

[dodge man]

If it is ignition it could be that is why the plug is wet, it stops sparking but sucks in some fuel still. When I had a spark plug go bad you could pull the electrode all the way out the top of the plug.

It’s my understanding that the exhaust side is where you will normally see piston and ring scoring but I suppose that can vary. As far as internal engine problems there just isn’t much that can go wrong, you have a piston, rod and crank. There just isn’t much else to go wrong.

When I rebuilt my saw I didn’t really time it but I probably spent 8 to 12 hours on it. You know how that works, I could do it again in 4 hours.

My wild guess is ignition but who knows. Let us know what the problem was if possible.

 

[Egon]

If it pulls easily compression may be the problem.

 

[dodge man]

If it pulls easily compression may be the problem.

Yes good point. Every once in a while when starting my 250, it will sting my hand when I hit the compression stroke just right.

 

[N80]

Not a compression issue. Always good firm crank.

It was the spark plug. Got a new one today. Runs fine.

I still can't get my head around why it was a spark plug issue. It would crank and run. That means it was getting spark. Why would a spark plug fire and then not fire?

Final analysis: I blew $50 on a carb but now I have a clean, new looking 25 year old chainsaw and a backup carb.

Anyway, the moral of the story is: If you don't know what you are doing, replace the cheap and easy stuff before doing a heart transplant even if it doesn't make sense.

 

[dodge man]

I can only remember having one spark plug going bad and it was in my MS250. My spark plug was so bad I don’t know how it ran at all. Mine was running funny off and on then it would not make good power than not stay running. I’m glad to hear you got it fixed.

 

[BlackOps]

kudo's!

 

[Ford850]

N80 thanks for posting the solution.

 

[N80]

N80 thanks for posting the solution.

You are welcome. I just wish it didn't involve admitting that I am a stooge.

 

[dodge man]

I think on the first page I suggested a spark plug, but hey, you got it eventually I put a thermostat in a car years ago because of no heat, a month later it happened again. I thought it can’t be the thermostat, I just put one in. After chasing my tail I of course figured it was the thermostat. I have had brand new parts that were defective. I don’t know if there is something about that model of saw that is hard on spark plugs or what.

 

[N80]

I think on the first page I suggested a spark plug, but hey, you got it eventually

Yep. I looked back and you did. And then again later. But in the words of the immortal Bones McCoy "Dammit Jim, I'm a doctor, not a ".........mechanic.

I will say this: I brought the saw down to my property this afternoon. One pull with the choke on then one pull with the choke off and it fires right up. It has not done that in years. So maybe some benefit to the new hoses and carb. Its like new now.