Iv tried everything.

[bobbyp_970]

Hello MS291 here. Iv torn my whole saw apart. I'm a Firefighter and have taken many Stihl repair trainings for wildland. Anyway iv got a saw that won't burp let alone start up. Iv cleaned everything down to the piston. Everything looks good no Cracks, no wear except where it looks like someone got the clutch brake a little too hot besides that brand new plug, new fuel, new filter, carb set to stock setting, has spark, piston looks brand new, exhaust clear. Not sure where to go from here. Any suggestions? Thank you in advance. Put the carb and plug on another 291 I have fired right up.

 

[Bob Hedgecutter]

Most probably cooked the PTO side crank seal and it wont run because it has a massive air leak around the crank if the clutch got that hot you can see it has been hot- seal is most likely poked.

 

[Bjorn T]

Hello, do a preasure and vaccium test. That Will show any leak on the crankcase.

 

[Bob Hedgecutter]

Hello, do a preasure and vaccium test. That Will show any leak on the crankcase.

True that, but many people lack the tooling required to perform such a test.
Might be easier to reassemble the saw to the point the cylinder is back together, but leave the muffler and carb off and take it to a local repair shop and have them perform the pressure and vac test for you, for a nominal fee.

However, if the clutch and oil pump are removed- it should become fairly obvious there has been excessive heat damage around the seal area.

 

[bobbyp_970]

this seal and the one on the other side?

 

[Bob Hedgecutter]

Yes, that seal. Looks to be rubbed through- or at least has some rotational grazing.
Easy way to confirm is to take the saw as it is now with all the other bits in a box with it and take it to your local Stihl shop and ask them to perform a pressure and vacuum test on it please.