Bogging Stihl

[dcnchair]

I've got a Stihl MS310 that's been a workhorse for years and never let me down. Two weeks ago I went to cut some wood and suddenly it would not stay running. Over the course of two weeks I replaced the plug, carburetor, vent filter, vent hose, fuel cap, fuel filter, fuel hose, air filter, coil. I dumped the old fuel and replaced it with the high priced Stihl factory fuel. I've set the carb a million times, and it just will not run. It has good compression, it will start, every now and then it'll rev, but it will not stay running. I've been running saws for 50 years, but this one has me stumped.

 

[Bob Hedgecutter]

Carbon coked spark arrestor screen?

 

[dcnchair]

It looks clean, but I'll take it out and see if it makes a difference.

 

[Bob Hedgecutter]

Mud dabber wasp nests in muffler?
Exhaust port choked with carbon?

I mean you have near thrown a new saws worth of spare parts at it- problem not solved- it starts and runs at idle/low rpm and wont rev out are pretty indicative of no escape route for burnt gasses.
However, if all the massed parts you have thrown at it are the cheapest you could find on Amazon- well Lord knows what might be happening.