Outdoor Power Equipment and Small Engines - Stihl FS80AVE w/TK carb won't run

Howdy all,

I have a Stihl fs80 AVE that seems to be in good shape except that the carb doesn't seem to be giving it enough fuel. It will run if I keep pumping the primer bulb, but dies soon after I stop. I don't notice it speeding up when it runs out of fuel like my chainsaw does. I have had it apart twice and cleaned it with carb cleaner. I didn't think to check the settings of the adjustment screws when I removed them (OOPS!), but I think I got them fairly close to where they were. The latest developement is that I can get it to run at higher rpm if I keep pumping the throttle gently. If I run it at wide open throttle, it warbles up and down from WOT almost to idle and back to WOT. Eventually it just quits. Weirdest thing I've ever seen, but I'm not a small engine mechanic.

Do I need to clean it again? Or does it just need to be adjusted? If I really can't get it to work, is there another carb that I can adapt to this engine? Any comments?

Thanks, Guy

Those symptoms could be from a few problems. I would start by taking out the spark arrestor and make sure it;s clean. Then make sure the fuel lines and primer don't have a pinhole or crack in them. Then make sure the fuel filter is ok. Then move back to the carb, and clean it and install a rebuild kit, not just the old gaskets and stiff diaphragms. If the problem persists after this, post back and we'll continue.

Thanks for the reply.

I have already replaced the fuel lines, as well as the pick-up in the tank (which I believe includes the filter), and the primer bulb. All were garbage when I got the machine. I will check the spark arrester as soon as I get a chance. I have noticed that there is some air coming up the fuel line when I use the primer - will have to look into that.

Last but not least; I tried to get a rebuild kit from a local Stihl dealer. He couldn't figure out which one I needed over the phone, so I took the whole power head in to him to see. When he came out from the back he had a flyer in hand, so I knew (thanks to another poster on this forum) that he was going to give me the " I don't know why you kept this so long, you should buy a new one" routine.

So... where do you guys find a kit for this?

Thanks, Guy

It should be a common kit for zama or walbro carbs, not just stihl. Most small engine shops should have a kit, or be able to get you one based on the numbers on the carburetor.

You have an "Old" FS80, most Stihl dealers, and most
lawn mower shops, have no idea there was an old one.

It is a Japanese trimmer, and is very like the Shindaiwa
T25 trimmer, and is also equipped with the TK carb.

Any mower shop can order you a kit, as the aftermarket suppliers have them. If you still have trouble getting one, let me know.

I missed the obvious..."TK carb" stated in the title of the thread. Thanks Fish....

I meant to get back sooner, but I have been so busy I couldn't even look at my machine. Finally got to it. So I took off the spark arrestor (also called a muffler) and discovered it had a lot of fuel in it. So the carb is overfueling the engine. I tried to start it with the muffler off and saw droplets coming out the exhaust. I was able to get it to run a little bit if I pulled on it with the throttle wide open. Still didn't run well.

So I took it apart to see what I could see. Unfortunatly, when I opened it up, I removed the jet without backing off the mixture needle. Great way to ruin two parts at once - the needle strips the thread on the jet, and the thread on the jet carves up the tip of the needle (both are brass). After cleaning the brass bits out, I reassembled and tried it - now it is completely dead.

I'm at the point where if I can't find a different carb quickly, I'll just have to get another machine.

Any ideas?

Guy

Ebay? Many small engine shops have 2-stroke junk piles for donor parts. Maybe you could get lucky that way? Ebay or a google search is probably going to be the most resulting effort.