TK carb adjustment question

[AlexP]

Gentlemen,
I apologize in advance if this question does not belong on this forum and if a moderator needs to delete it I understand. I know there are a lot of experts here and maybe someone could shed some light on a TK carb adjustment. After joining this forum and learning about performing a muffler mod on my chainsaw (which now runs fantastic after the mod) I couldn't resist doing the same thing to my Green Machine 3000 s/s string trimmer. It now screams like a banshee and revs much higher.

My question involves richening of the fuel mixture. This carburetor only has an idle speed adjustment screw and what the factory calls an idle mixture screw. This carb does not have a high speed mixture screw like on a chainsaw carb.

Can I richen the high speed mixture with just opening the idle mixture screw more? The factory adjustment is 1/2 turn out from full close and I now have it set at 1 full turn out. I revved the engine up and tried to get it to burble by opening up the mixture screw like on a chainsaw as much as 1 and 1/2 turns but didn't really notice any difference. The plug color is a very light tan. A little too light for my comfort. I am starting to get concerned about possibly leaning out too much at high rpm and seizing the engine. Any advice on whether I am proceeding in the right direction by opening up the idle mixture screw? Any other suggestions? Thank you in advance.

Alex

 

[Lakeside53]

The low speed screw or idle adjust has nothing to do with the H run jets. Not sure which model TK you have but many are "rotary valve" types and the H adjustment is a needle that goes though the valve vertically. Some have a fixed H mixture jet and you can't adjust it.

What is the exact carb model?

 

[AlexP]

Lakeside,
The only numbers stamped on the carb are on the base and they are
0A10A. The rebuilding kit I bought for it which worked perfect said it was for a TK-2 carb. This carb has a small round fuel mounted pump on the side.
The throttle operates with a cable thru the top of the carb sliding out a circular throttle plate with a long needle thru the center. Hope that helps with the ID.

If it has a fixed high speed jet of some sort can it be drilled out slightly?
Should I just undo the muffler mod? I can easily cap the new muffler opening but that would hurt since the machine seems to be running so nice. This forum is definitely dangerous for the tinkering kind like me.

Alex

 

[Uwharrie]

Hi AlexP, The Green Machine 3000SS used a Shindaiwa T-25 engine. The TK carb has an adjustment of the needle by the positioning of the clip that holds it. The best way is to unconnect the throttle cable from the trigger ( very easy ), now unscrew the aluminum nut on top of the carb that holds the throttle cable on top of the carb. When you remove the top cap the slide will come out with it, you must then remove the cable from the slide and the spring will come out of the slide. Now the needle will push out of the barrel or slide and you will see three round places on the needle. Most of the time the needle clip will be in the center slot, if you move it down to the bottom it will make the engine run richer by allowing more fuel in the engine. If you move it up it will run leaner. Another thing to look for is the main jet which is located right beside of the inlet needle inside of the carb, it will screw out with a 8mm or 5/16" socket, make sure it's clean. Carb kits are readily available at most shops for this carb if you need one. Hope this helps. Tony

 

[AlexP]

Uwharrie,
Your instructions were right on the money. Thank you very much. I reset the clip to the lower setting and the plug color is now a light tan and the engine definitely is running a bit richer and really screams. looks like I can keep the muffler mod as is. It was well worth the effort adding the extra exhaust outlet. My thanks also to Lakeside.

Alex

 

[Wolf Bley]

The Shindaiwa instruction page for this carb: page 14, 15
http://www.shindaiwa-usa.com/getatt...12c-bc45-b2e34cb336ea/C25 C35 T25e_030187.pdf

 

[HarleyT]

Great link!! The old Stihl fs80 has different basic carb settings, just so you guys know...

 

[Wolf Bley]

Really the STIHL carb is different? Tell me how so. Mine looks just like the one in the SHINDAIWA PDF I posted. wolf

 

[HarleyT]

I have since E-Bayed my old Shindaiwa and Stihl manuals, but my vague memory remembers them as being different.

 

[HarleyT]

Both carbs are the same, pretty much....

 

[Ax-man]

Old thread but it is appropriate. Don't ask me why but I have been on a trimmer kick lately and got into an old style FS 80 that has been sitting around in the machine shed for a good five or more years . It has one of these TK slide valve carbs which is NLA. I did find a rebuild kit because the carb was basically clean just stiff diaphragms so I decided to gamble and see if I can make it run . No luck so far but I am not throwing in the towel just yet. I don't seem to be able to get fuel into the carb itself . Fuel filter isn't plugged. I had to bypass the primer because it wasn't working.

My question is anyone know how that metering lever is suppose to be set . I finally got the needle to seat but it just about on top of what looks to be some kind of accelerator pump going down into the main body of the carb. I can trip the metering lever to take the needle off it's seat but what ever that rod is sitting under that metering lever isn't going to move the inlet needle that I can tell just by the metering diaphragm moving up and down when the engine is running .

Any little tid bits of info on this carb would be helpful like the carb stings for the FS 80. A similar carb on a Shindawai is 1/2 turn out on the L and 2/12 on the H. this FS 80 TK carb is fully adjustable.

 

[Jasonrkba]

I have a thread on here detailing everything you need to know somewhere.

 

[Jasonrkba]

https://www.arboristsite.com/community/threads/tk-carburetor-adj.329282/

 

[Jasonrkba]

If you can't get the tk to work you can convert it to a newer style carburetor. I have one on an fs 80 I did while board one day. Works great.

 

[DND 9000]

My question is anyone know how that metering lever is suppose to be set .

The distance between the metering lever and metering diaphragms mounting face is 2mm.


Basic setting is: H (long screw) 2 turns open, L (short screw) 1 turn open

 

[RipRap]

If you can't get the tk to work you can convert it to a newer style carburetor. I have one on an fs 80 I did while board one day. Works great.

Which carb are you using? Can you take a couple more photos of your set-up and the details.

 

[Ax-man]

Thanks guys for the info it was helpful. I'll go back and tinker some more on this carb. Wish me luck

That rod or plunger I was talking about is visible in DND's pic it is right under the metering lever . How the metering diaphragm is going to move the needle off it's seat with that right under it is beyond me. Strange animal these TK carbs. Not easy like a cube carb for a chainsaw.

Pics of Jason's set-up would be nice I have some carbs that might work.

 

[DND 9000]

That rod or plunger I was talking about is visible in DND's pic it is right under the metering lever .

That is the valve jet. It can be removed for cleaning. If you do this, also remove the mixture adjusting screws for good cleaning results. If you unscrew the valve jet, be careful these parts are no longer availible as spare parts. Also take care of the small sealing ring under the valve jet, NLA too.

 

[Ax-man]

Thanks, I tinkered with the carb again . The lever is set at 2mm . I didn't take that valve jet plunger out . I did take the main high speed jet out that sits next to that lever it comes out with a 8mm socket and it was clean .

You mentioned sealing ring under valve jet . If I am reading you right is there a rubber seat that goes under that 8mm main jet that screws out, there wasn't anything there when I took it out but I have one rubber piece left in that kit I bought . Does that fit under that jet?? It looks like it belongs there . I didn't put it in because I wasn't sure . I know someone has messed around with this carb because the metering lever was way to high before I reset it.

I think this carb will work because I primed the pump side when I put it back together and the trimmer ran for a brief time. I can't get fuel to pull into the carb without that primer . I have drawn fuel up to the carb but it just won't get into the carb itself . I can't get the tank to hold pressure because the fuel cap is split . Tried other caps with the same result . I think this is my biggest problem no primer and no tank pressure. To me it should at least run primer or not and no tank pressure but I could be wrong.

I recently got a Shindaiwa 35 trimmer running but I bought a new TK carb for that one . It has no real type of priming system and that tank won't hold pressure either and it runs good . I have the parts to fix the tank but I need a fuel filter to finish it and that part is on back order . I was hoping this FS 80 would at least run like that Shindawai but so far no luck .

 

[DND 9000]

I don`t know the kit you have, but I think that should fit. You can also have a look at the exploded diagram of that TK carburetor. The sealing ring for the valve jet is part 1 in the drawing. Is everything in good sealing order between the parts 13-16? Thats the fuel pump with gasket and diaphragm. Do you have the impulse signal present?