farmboss running to fast

[jrclen]

Went out to cut wood yesterday and the farmboss ran fine for a couple hours. I took a break and when I restarted the saw I noticed it was idling way to fast. Never had a problem with that before. I only had 5 or 6 more cuts on the trunk so I kept going. Then I noticed that it seemed to be over revving even while cutting. Even in the cut I could tell something was different. The switch broke a while back so I usually kill it by choking it. But now it won't stop when choked. It just slows down a bit and keeps running like a raped ape. I had to pull the plug wire off. Running to lean? Any ideas on why it changed all by itself? Thanks.

old 041 farmboss, bought used, don't know the maintenance history.

 

[Haywire Haywood]

Partially plugged carb inlet screen?

Ian

 

[andrethegiant70]

You need to suss the problem out before you run the saw again. It sounds to me fairly likely that you have a vac leak. It being an 041, which is notorious for shaking its intake system loose, I'd start with making sure the intake bolts are all dogged down. I would also look at your fuel line to see if it is cracked or hard.. you may be starving the saw. If you can't find the cause with some good old fashioned poking around, I'd take it to have it pressure tested before you run it again. You may have developed a crankcase leak, most likely the bearing seals....it's expensive to fix, so I'd be VERY diligent trying find whatever else may be your problem!

 

[andrethegiant70]

Oops. I saw farmboss and I assumed it is an 041. I think there are other Farmbosses. If it is not an 041, it all still applies, it is just a bit less likely that it is the intake system. You still have to check it, though, its a very real possibility.

 

[THALL10326]

Went out to cut wood yesterday and the farmboss ran fine for a couple hours. I took a break and when I restarted the saw I noticed it was idling way to fast. Never had a problem with that before. I only had 5 or 6 more cuts on the trunk so I kept going. Then I noticed that it seemed to be over revving even while cutting. Even in the cut I could tell something was different. The switch broke a while back so I usually kill it by choking it. But now it won't stop when choked. It just slows down a bit and keeps running like a raped ape. I had to pull the plug wire off. Running to lean? Any ideas on why it changed all by itself? Thanks.

How old is the saw and has the fuel line ever been replaced??

 

[mikemouse]

fromdirt bike experience , it IS leaking air. dont forget to chaeck the crank seals when it gets a physical.hope it's something stupid and simple but crank seals can be easily forgotten.any body have thoughts on how to check for leaks? Iused carb cleaner or starting fluid to check old Chevy manifolds and carbs. A piece of carboard makes a good sheild and helps narrow down specific areas but the down side is it has to be running to hear the change in RPM.

 

[jrclen]

How old is the saw and has the fuel line ever been replaced??

It's pretty old Thall. The fuel line looked good last year when I fixed the leak where it enters the tank. I will check it again. Thanks for the tips guys. I will put it on the bench before I try it again. It does like to shake things loose. I finally got the muffler to stay on with locktite and lock washers. It irritates me once in a while but I've become fond of the way it chews through my dead oak trees.

 

[THALL10326]

Welp we need to find out what Farmboss is in question, the old 041 or the 029/290. The old 041's had a deal where the carburetor mounting block would come loose from the cylinder and create a helluva air leak. The 029/290's are famous for busted fuel lines which cause the saw to run lean first and then start dying as the hose got worse. So we need to know which Farmboss..

 

[jrclen]

You need to suss the problem out before you run the saw again. It sounds to me fairly likely that you have a vac leak. It being an 041, which is notorious for shaking its intake system loose, I'd start with making sure the intake bolts are all dogged down. I would also look at your fuel line to see if it is cracked or hard.. you may be starving the saw. If you can't find the cause with some good old fashioned poking around, I'd take it to have it pressure tested before you run it again. You may have developed a crankcase leak, most likely the bearing seals....it's expensive to fix, so I'd be VERY diligent trying find whatever else may be your problem!

It is an 041. I only paid $100 for it but I'd like to keep it if I can fix it cheap. I'll poke around the things you suggested. Thanks.

 

[THALL10326]

It is an 041. I only paid $100 for it but I'd like to keep it if I can fix it cheap. I'll poke around the things you suggested. Thanks.

Awww ok. Take the air filter off, grab the carb and see if it moves at all, if it does ya mounting block to the cylinder is loose...

 

[jrclen]

Awww ok. Take the air filter off, grab the carb and see if it moves at all, if it does ya mounting block to the cylinder is loose...

Carb is tight and the fuel line looks good.

 

[THALL10326]

Carb is tight and the fuel line looks good.

ok, right where the impluse hose attaches to the carb, sometimes they crack right there, on that bend, go look..

 

[jrclen]

ok, right where the impluse hose attaches to the carb, sometimes they crack right there, on that bend, go look..

Took it off and it looked good. No leaks in there either. Both hoses look kinda new.

 

[andrethegiant70]

Pressure test it is! If it comes back clean, you missed something.

 

[THALL10326]

Took it off and it looked good. No leaks in there either. Both hoses look kinda new.

Ok if all that is good your down to carb problems or crank seals. I assume your fuel filter is good so not much left other than carb or seals..

 

[jrclen]

Ok if all that is good your down to carb problems or crank seals. I assume your fuel filter is good so not much left other than carb or seals..

I'll check the fuel filter in the morning. Then maybe take it to my friendly Stihl dealer. He's a pretty good guy.

 

[Lakeside53]

If the rest checks out,make sure your carb butterfly is fully closing, and the throttle shaft isn't worn/sticking or sucking air.

 

[jrclen]

If the rest checks out,make sure your carb butterfly is fully closing, and the throttle shaft isn't worn/sticking or sucking air.

OK. I know it closing ok. And the linkage seems fine. When Thall had me take the air cleaner off I took a look at that and worked it. I will look at the shaft and see if it wiggles. Thanks.