Chainsaw died;

[oldballs]

This is a 11 year old Farm Boss Stihl MS290. It has been quite dependable and I have taken good care of it even though it has a lot of hours on it.

A couple days ago I was cutting a 30 inch White Pine Stump close to the ground so as to get my Stump Grinder on it. I have done this many times.

The bar is 20 inch, so I was working my way around it when all of a sudden it just died. In checking it out I can see nothing wrong...except that it seems to have not much compression when I pull the rope. It won't fire at all. Any ideas??

Cheers,
Mike

 

[Wagtail]

Have you checked the screen? Carbon build up (wire brush removal of any residue) is a quick check.

 

[oldballs]

Thanks Wag. The screen was clear/clean....as I usually keep it that way.
Cheers to you Wag
Mike

 

[MoKelly]

Do you have a gauge to check compression when you pull start? That can tell you if it’s an internal issue.

Good luck.

MoKelly

 

[oldballs]

Heck, I think I have a gauge for some old car engines around here somewhere....but I really don't know much about it other than routine maintenance. I wonder what the compression should be, just in case I get into it. I can see the piston go up/down thru the exhaust/muffler hole. Maybe the piston has rings??? I don't pretend to be much more than shade tree mechanic.

Thanks Mo

 

[ericm979]

Turn the crank so the piston skirt is visible through the exhaust port with the top of the piston right at the top of the port, take a good picture and post it here so we can look at it. If it's seized it'll usually show damage on the exhaust side piston skirt. That's the hot side so it goes first.

Compression should be above 120 psi. With a small engine like this you need a compression tester that has a Schrader valve in the hose at the spark plug end. Some don't.

 

[dodge man]

Check the spark plug first, make sure it hasn't started to come out. I’ve attached a pic of a MS250 that had piston damage. As bad as it was, it still had decent compression and ran but idled badly. This looking in the exhaust port.

 

[oldballs]

Thanks gents. I'll get back to you with a pic. Already checked the spark plug....cleaned again and gapped a different one. Will look for my compression tester.

Right now having problems with my eyes i.e. macular degeneration, cataract and waiting on a call from the doctor.

Cheers,
Mike

 

[thclimer]

If you hold the saw by the handle of the pull cord with only the weight of the saw does it unwind the cord rather quickly (5 sec)? Its a crude test but I have seen the weight of the saw unwind the cord and it a pretty good indication of poor compression.

 

[oldballs]

Okay guys,....still waiting for the eye doctor office to return my call. You know how that goes

So I went outside to do the above cord test that "thclimer" posted. It took about 6 seconds for the weight of the saw (without the bar & chain) to drop to the ground....tested several times.

Then with the sunshine I got some pics....some not very focused. It may be better to buy a new saw that take this one to a repair shop....Geeze I would hate to do that.

My compression tester is just a rubber hand held device with no Schrader valve.

Cheers,
Mike