Chainsaw hard to start (2)

[ChiefH]

I have two Sthil MS251 chainsaws and both are almost impossible to start. I have changed the spark plug, installed a new Air Filter, I use fresh gas (ethanol free).
I use the 3-4 short pulls to prime and then the big pull to start, but they do not start. The saws are about 8-9 years apart in manufacture and both seem to have this same problem. My neighbor who has a lot more chainsaw operation time that I do, tried to start one of them and he could not get it started. It seems the compression is very high as the pull rope is very hard to pull. I have other Sthil equipment and none are as hard to start as these two chainsaws.

Since the vintage of the two is far enough apart and the older one has seen a lot more service, I do not think it is wear and tear, but I do not know the problem.

 

[Hammermechanicman]

Are they standard 251's with no primer bulb or 251ce's with a primer bulb and EZ pull starter?

 

[ILENGINE]

10-1 chance that you are flooding them with those 3-4 short pulls. Using a normal pull they will probably poof and they can take it off of choke and start it. The saw will just let out a poof. It will not start and run. It will not start and die. You may not even get what sounds like a full pop. It will be a soft sounding poof when it fires. The next pull if the choke is not turned off will flood the saw.

And the MS250 series are a high compression saw and requires a good effect to crank them over properly. If no ez start then will require a good pull to crank and start. with ez start a slow pull until the internal springs turns the engine over works best.

 

[Rivets]

Have you checked the spark arrester to see if it is plugged?