Thread: Stihl 250 Problem

Originally Posted by dvdhack

Hi all chainsaw experts out there. I have a small Stihl 20 I use to cut firewood and all has been well until the latest attempt to use it. I can get it started OK with the choke on and it revs hard on start but as soon as I take the choke off it stalls.

Anyone got any idea what it might be? Its had very little use.

Many Thanks

Ralf

Ralf, I assume you have fresh (as in bought and mixed yesterday?) fuel and a very clean air filter?

Apart from just hard revs, will it actually run wide open throttle (WOT) and cut a big chunk of wood with the choke on? It's one thing to rev hard under no load so that it sounds like its running OK, and then something else to be revving hard under full load at WOT.

The fact that it revs on choke means that at that setting the air fuel ratio is within it's running range but as soon as you take the choke of, the air/fuel ratio drop outside the range. This suggests to me that is getting too much air relative to the amount of fuel. Fuel starvation can be due to many things and one of these is a gummed up or carby not working properly. I suggest starting with a carby clean and depending on how old it is, maybe a new carby kit. Use of the saw has very little to do with this, the gaskets and diaphragms in a carby sitting permanently in fuel go soft and swell and lose flex after a while so they have to be changed.

Fuel starvation is not good for a chain saw engine and can wreck it if its not done right. If it were me I'd recommend a professional tune up to get it singing.

Thanks BobL

I havent tried cutting a piece of wood on idle - as soon as I operate the trigger it goes to the normal operating condition.

I'll take you advice and get it serviced, I just thought it might be something real simple.

Regards

Ralf

blocked fuel filter

sounds like the low adjustment need to be cranked up.

take it to get serviced if you dont know what you are doing.

I would try the most simple things that don't cost much first.

Such as replacing the fuel/oil first in case it has gone stale or you got a dud batch of fuel.