One of my weirdo 4mix engines went south on me. A Stihl FS 131 brush cutter.
It was hard starting and would not idle, once it got to operating temp.
I did a full tune up. One valve was off, otherwise no obvious issue. It did then start fine, but still no idle after warm up and it sounds like it is missing, at WOT.
I put a new carb on, but no change. Piston looks like the dreaded carbon issue.
It has always been run on Ultra at 50:1. It's maybe 5yrs old.
The spark looked good, so I assume the coil is fine.
I am right at the point where I am ready to pull the crank & piston to check the valves. So far, it all looks fine. The cam looks new.
Any suggestions on what else to look for, besides carbon build up?
BTW I did try the "decarbonizer", twice. Didn't seem like it did anything. In fact only a tiny bit came out the next day. I think it just seeped past the rings. I'll find out tomorrow when I pull the bottom end.
It was hard starting and would not idle, once it got to operating temp.
I did a full tune up. One valve was off, otherwise no obvious issue. It did then start fine, but still no idle after warm up and it sounds like it is missing, at WOT.
I put a new carb on, but no change. Piston looks like the dreaded carbon issue.
It has always been run on Ultra at 50:1. It's maybe 5yrs old.
The spark looked good, so I assume the coil is fine.
I am right at the point where I am ready to pull the crank & piston to check the valves. So far, it all looks fine. The cam looks new.
Any suggestions on what else to look for, besides carbon build up?
BTW I did try the "decarbonizer", twice. Didn't seem like it did anything. In fact only a tiny bit came out the next day. I think it just seeped past the rings. I'll find out tomorrow when I pull the bottom end.
