Old Stihl FS80 Carb Flooding

[Hyprdrv]

I also have a FS 80 AV Stihl with the KT carberator I believe you guys are refering to here. When I start the motor I notice fuel being sucked back up the vent tube. Is this a related problem to the check valve mentioned above? After priming and using the bottom plunger the motor will start for about 20 seconds then die as if out of fuel. If I slightly press the bottom plunger it may run again for a few seconds. I've replaced all the gaskets and seals but nothing seems to help. It was mentioned to replace the "needle" above. Which needle and does anyone have a diagram or exploded view of the carberator?

Thanks in advance,
Steve

 

[Fish]

Your trimmer is older than most of the kids here, so I'll tell you what I have done, since Stihl stepped away from this trimmer a decade or two ago.

The needle you are referring to is part of the "Purge" circuit, not a "primer". When they go bad, they will let air suck in and affect the
system.

The "meatball surgery" fix is to just stick a roofing nail into the end of the line and go on. The choke is sufficient to start the trimmer,
it may take a few extra pulls, but you have little or no alternatives.

 

[Goball]

Stihl FS80

Your trimmer is older than most of the kids here, so I'll tell you what I have done, since Stihl stepped away from this trimmer a decade or two ago.

The needle you are referring to is part of the "Purge" circuit, not a "primer". When they go bad, they will let air suck in and affect the
system.

The "meatball surgery" fix is to just stick a roofing nail into the end of the line and go on. The choke is sufficient to start the trimmer,
it may take a few extra pulls, but you have little or no alternatives.

Thanks for the advice. I'll have to dig it out of the pile one of these days as I had all but given up on the animal.

 

[dbittle]

Same Problem on HT75

I had this problem on my HT75 polesaw (same powerhead). At the time, (last fall) new Walbro carburetors were going for $50 on ebay. That was the way I went, since the cost difference between the kit and the new carb was $35 or so and lowered the hassle factor. It worked great, so that's a good option.

 

[Hyprdrv]

Thanks Guys,
I'll try replacing the needle valve and see what happens. If I can find a TK carb I'd go that route. I'll post any results.

Steve

 

[dbittle]

Wrong Carburetor...

It was a Zama carburetor on my Ht-75, not a walbro. My reading on the problem before I just punted and replaced the thing made me think the primer is supposed to pull fresh gas from the tank, fill the carburetor with it, and then return the excess gas to the tank. When the check valve fails, it drips gas when the engine is running. One thing to be careful of is that some of the Zama carbs have a single mixture screw instead of high and low circuit screws. The Zama website has information on what carburetors fit what engines and there is one on ebay right now for $49.95 that has the high and low circuit adjustments.

David

 

[Fish]

Thanks Guys,
I'll try replacing the needle valve and see what happens. If I can find a TK carb I'd go that route. I'll post any results.

Steve

The needle valve has been nla for many, many years, as well as the carb, which is why I suggested just plugging the excess line so that it won't suck air back into the carb.

Or you could check with the local Shindaiwa dealer and see if he can get a carb for the T-25 trimmer which had a similar carb which could be
made to work on your trimmer, which would be expensive if still available.

 

[Fish]

Oh yeah, for those that may be confused, there were two totally different fs80 Stihl trimmers, the old one was a Japanese trimmer Stihl put out in the 1980s, that is the one that we are talking about here.

 

[Eccentric]

Oh yeah, for those that may be confused, there were two totally different fs80 Stihl trimmers, the old one was a Japanese trimmer Stihl put out in the 1980s, that is the one that we are talking about here.

Yep. I have one of those. My grandpa bought it new in 1984 or so. FS80AVR with electronic ign. No relation at all to the later FS80 trimmers. I have an older (and clapped out) Shindaiwa Green Machine trimmer that has given up a few parts to keep that ancient Stihl/Shinny running over the years. I should have bought the NOS P/C that were on feebay a while ago for $25 or so. Going to have to break down and pick up an FS250 soon. The FS80AVR was a good machine. Heavy, but pretty strong for a 25cc trimmer. That machine would have been much better with 10-15 more cc. I guess that'd be a Shinny BP45. I rebuilt the TK carb on it about 15 years ago. Full kit was still available from Stihl at that time.

 

[Fish]

I have been selling the he ll out of the full aftermarket kit for the TK, mostly because no one else knows much about it.

 

[dozerdan]

Fish
When Stihl had the East Coast distributor here in Pa they offered a change over kit for those trimmers. It came with a Walbro, throttle cable, air filter and I think another intake block. I installed a few of them years ago. I have a few local guys that still have them and use them daily. My understanding was that the distributor put those kits together from parts from different Stihl trimmers.
If I get one in the shop I will take some pictures and post them for you.

I Put this one together a few years ago and I still use it once in a while.

Later
Dan

 

[Fish]

Great, I am sure it is possible, those are/were some well made trimmers...

 

[whatscooking]

Think i found the problem on mine.

i have only run it for for a short time,3\4 tank, but it started second pull after i put the carb back on. I want to try it cold tomorrow and see but i think i got it, at least on mine. What i did, grind down or pull out the check valve, it has a small rubber O ring that has let go and pushed up and the needle valve will not open and let fuel in. Set the needle slightly above level. Plug the puke tube on the outside so it cannot pull air back into the carb. Here is where i found to look to make it run, Pull the top off and pull out the sliding valve and figure out how to unhook the cable by pushing down on it and popping it out easy, raise the needle with the small E clip and finally what i think the problem is, where the throttle cable comes out the top, my little boot was holding fine but everything else leaks everywhere, with the carb off but throttle cable hooked up close the two mixture screws find a rubber hose and push in one end of the throttle throat and hold finger on the other and spray your soap mix you have on the top of the carb then blow and see the bubbles come off of the throttle cable area. First time i left the cable off of the valve and put a bolt in the top rubber on the carb and that is where it started second pull. I ordered a cable and wrapped the old one with black tape and it acts like a new one, idles down and revs up all i want. Watch it not start tomorrow but it did not miss a beat today.

 

[mudrat2]

Not to open an old thread but put the information here for someone else looking for it.
Valve originally in question is part of what is often called the tickler circuit, used to purge air from the carb and allow fuel from the pressurised tank into the carb.
You can pull the tickler valve out and replace the o-ring. The original o-ring seems to get eaten by ethanol.
Grip the brass pin and pull straight up. I used a small collet chuck used to hold small drill bits.
Replace o-ring and push straight back in.

Carb flooding as originally described is usually caused by the needle valve not seating. Possibly damaged tip, or valve seat.
Valve seat can be repaired as it not in the repair kits I have used, it is brass and easily polished by using a steel tool of correct angle.

Look for missing or damaged spring under the small lever that runs from needle valve to center of carb.

 

[president]

I have an fs 96 ,thats shindiawa built .No current info except an
old IPL on stihls site.Good machine!