TK carburetor adj

[Jasonrkba]

Im reviving an old shindaiwa T20 trimmer. It starts easy idles great but I have to hit the throttle slowly or it will bog. These slide valve carbs are a different animal. Any suggestions? It has been rebuilt and new lines. I also cleaned the muffler and screen. New plug. I believe it needs a clutch, the head always spins.

 

[alderman]

Im reviving an old shindaiwa T20 trimmer. It starts easy idles great but I have to hit the throttle slowly or it will bog. These slide valve carbs are a different animal. Any suggestions? It has been rebuilt and new lines. I also cleaned the muffler and screen. New plug. I believe it needs a clutch, the head always spins.

Might just need a clutch spring. Have you let it warm up and see if it still bogs with throttle? Adjust the low end out a bit at a time to see if that helps.


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[Jasonrkba]

I learned this lesson the hard way. It has a "slow air adjustment" idle and main jet. None of which are marked. I did a wright up about this on another site. The slow air is adj out 1/2 turn. The main jet is 2 1/4. This is the recommended starting point per service manual. The problem is it ran fairly well but was starved for fuel. And Ultimately caused damage. Further research said to hit the throttle to wot then further back out the main until the engine starts to bog and go back until it sounds good again. The top two are the idle, slow air and the lower is the main. This was on a Shindaiwa but many of the older stihl trimmers have the same setup. I searched high and low for this information and could not find help anywhere so hopefully this helps someone someday.
My Stihl FS80 AV calls for one turn for the low (top needle) and two turns for the high (lower needle).

 

[Captain Bruce]

Here I am looking for the same answers in '21. FS80AVRE. No history of use or service. Came in wanting to get running for son of original owner.....one of those wonderful stories.
Removed carb and installed the correct kit. #615-054 OR 462170. $10 anywhere.
The old gaskets and diaph. were in bad shape. Found 1 o-ring behind the fuel pump crimped in its seat, so someone else has been in there. Primer lines were assed up.
Put new primer bulb and lines in place. NOTE: primer bulb clips into z-shaped metal bracket attached to tank.
Line routing = tank line from clean tank, thru single-hole grommet, to bottom/short nipple on primer.
carb line from brass 1/4" pipe nipple on carb, UNDER and to the Right of the fuel pump, to the top/long nipple on primer bulb. NOTE: down-pointing brass pipe nipple in front fuel pump cover does nothing. I have seen some machines with a short hose this fitting to allow spillage/overflow, onto the ground, and your leg.

Unit will start on full choke, with 3 primes....and will idle than die, regardless of choke position. Lack of fuel.........

Pulled both low and hi air bleeds...both were/are 4 turns out from seated...they look fine. The tank vent, which is actually in the cap, was pulled apart and cleaned. Vent is a small duck bill...made sure it was clean and free to open. Blew out 2 small holes in inner cap neck with tether. OPENED up centered pass-thru hole in cap. Pulled tank line assembly/grommet out of tank. Replaced fuel filter which is the metal weighted type. Blew tank out to dry and clean condition. Fresh fuel. NIB spark plug fires bright blue.

Same result.

 

[Jasonrkba]

After that one I swore I'd never fix a TK carb again.lol

Are you sure its not flooding?

 

[emoz]

So I have been tinkering with a TK25 carb on an FS80 string trimmer. Symptoms won't stay running for but a second or two. Seems like its fuel starved... as we then looked at the carb. Funny thing happened after I had somebody else with more experience look at it. He pulled the screen off the exhaust. It still didn't run and he gave up but it reminded me of my husq 350 chainsaw that wouldn't run because that same screen was packed with carbon. Got me twice thinking it was carb. Turned out to be exhaust being plugged both times. Cut to the chase... I took the muffler off. It felt heavy. Got the FS80 run for a few more seconds without the exhaust. Decided to replace muffler. Bang... now all I need to do is tune properly. That's why I am here. Keep in mind that the carb needs back pressure to run the fuel pump. If the exhaust is plugged it will choke it and keep the fuel from pumping because it can't complete the cycle. Tricky to identify but once you get stung a couple times it's easy to find...

 

[scherbd]

Here I am looking for the same answers in '21. FS80AVRE. No history of use or service. Came in wanting to get running for son of original owner.....one of those wonderful stories.
Removed carb and installed the correct kit. #615-054 OR 462170. $10 anywhere.
The old gaskets and diaph. were in bad shape. Found 1 o-ring behind the fuel pump crimped in its seat, so someone else has been in there. Primer lines were assed up.
Put new primer bulb and lines in place. NOTE: primer bulb clips into z-shaped metal bracket attached to tank.
Line routing = tank line from clean tank, thru single-hole grommet, to bottom/short nipple on primer.
carb line from brass 1/4" pipe nipple on carb, UNDER and to the Right of the fuel pump, to the top/long nipple on primer bulb. NOTE: down-pointing brass pipe nipple in front fuel pump cover does nothing. I have seen some machines with a short hose this fitting to allow spillage/overflow, onto the ground, and your leg.

Unit will start on full choke, with 3 primes....and will idle than die, regardless of choke position. Lack of fuel.........

Pulled both low and hi air bleeds...both were/are 4 turns out from seated...they look fine. The tank vent, which is actually in the cap, was pulled apart and cleaned. Vent is a small duck bill...made sure it was clean and free to open. Blew out 2 small holes in inner cap neck with tether. OPENED up centered pass-thru hole in cap. Pulled tank line assembly/grommet out of tank. Replaced fuel filter which is the metal weighted type. Blew tank out to dry and clean condition. Fresh fuel. NIB spark plug fires bright blue.

Same result.

Captain Bruce,
I just acquired an older Stihl FS 80 with the TK carb. The lines completely deteriorated, except for the "overflow" line to no where. How ever I attached the primer bulb to the brass nipple out of the fuel pump cover. I rebuilt the carb. The unit started up and runs. The only thing is I get fuel out of the "overflow" tube. I haven't spent any more time on it, but was thinking of routing the overflow line right back into the plastic tank. (still have to adjust carburetor and do a load test) Thanks, Dan

 

[alderman]

Some of the Shindaiwas route back to the tank and others don’t. I’ve never had an issue with it coming out the tube while running it. I thought that was just to handle the priming fuel.


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[scherbd]

ok, I am going to tune the carb more and see if that takes care of the issue or add a grommet to the fuel tank and route it there. Thanks

 

[mudrat2]

Old thread but this info may help someone. The old TK carbs with the tickler button on the bottom have an o-ring under the purge valve that is destroyed by ethanol.

This causes fuel to leak out of the overflow tube while running.

The o-ring was not in any kit I could find and you need to pull the brass valve out of the carb body to get to it. I used a small collet chuck to grip the valve shaft. I also routed the overflow tube back into the tank and added a priming button pump to the overflow tube to pull fuel into the carb.