stihl MS291

Grousetrap · July 23, 2024, 03:28:17 PM

Hi- I need some advice on a stihl ms 291. This saw had a burned out piston with stuck rings. I pulled the jug off and replaced the piston (with new rings of course). when reassembled, the saw ran perfectly for about 5 minutes, then slowly died out. I thought the issue may have been a leak in the area where the seal between the jug and the base. So i pulled the jug off again, cleaned up this area, applied high temp gasket maker, reassembled, let sit for 24 hours...... started saw, and it ran perfectly for about 5 minutes and died. Saw has roughly 150 pounds of compression. Spark arrestor has been removed. Any ideas??? Thanx much

JD Guy · July 23, 2024, 05:30:36 PM

Well,typed a reply but some how it went bye bye!
Look at fuel delivery, perhaps new fuel line, filter. Perhaps some gunk got into carburetor and that needs a good cleaning as well.

More experienced folks will come along soon, hopefully!

Grousetrap · July 23, 2024, 07:33:15 PM

......guess I should have mentioned that the new carb did the exact same as the original.....runs perfect for 5 minutes after re-assemble, then quits.

Guydreads · July 24, 2024, 04:35:24 AM

Couple questions: First, what's the color of the spark plug when you take it out after dying out? Light brown, dry? Or dark and wet? To me it sounds like a coil dying once warm, but I could be ever so wrong.

Grousetrap · July 24, 2024, 10:05:39 AM

....but it wont start back up after cooling down for days. However, it did start back up (and run really well for 5 minutes) after I pulled the jug the second time. If it were the coil heating up, wouldnt it cooperate after cooling back down?? Thanx much for the input

Magicman · July 24, 2024, 02:18:10 PM

I am assuming that your fuel tank vent is OK?

lxskllr · July 24, 2024, 08:56:09 PM

Opening the tank and closing it would check the vent, right? If it starts after doing that, it's likely a vent problem.

Magicman · July 26, 2024, 09:39:50 PM

After the saw warms up the fuel/fuel tank should heat up and expand actually pressurizing the fuel tank. I know that an empty tank will spew when I open the cap.

Just trying to figure out what the 5 minute problem is.