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Discussion Starter #1 (Edited)
Gentlemen,
I have an older Green machine Model 3000 S/S that has a TK carburetor that I have an adjustment question on. I just added a second muffler port and the machine now screams like a banshee. 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 like a chainsaw by opening up the mixture screw as much as 1 and 1/2 turns but didn't really notice much difference. 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.

Alex
 

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The mixture screw on a TK slide valve carburetor is actually an air bleed, it is used to lean out the mix at idle as the needle and jet get wear and start running richer.

On most of the older TK slide valves there is a setting you can make to the needle on the slide valve, remove the cap off of the carburetor and pull out the slider, remove the throttle cable and pull the needle out of the top of the slide valve. Look at the needle you should see a small e-clip on the needle and there is usually three notches on the needle (factory setting is middle notch) to richen up the high speed mixture, put the e-clip in the lowest notch, reassemble carburetor slide valve and install back in carburetor.

I don't know if that will make enough difference, but as far as I know that is the only adjustment you can make to high speed mix.
 

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Discussion Starter #3
30yeartech,
Your description nailed it for me. I went out and took the throttle cable apart and the needle and clip were exactly like you described set in the middle slot. I set it in the lowest slot like you said and will run the trimmer in the morning and see how the plug color looks. If the mixture is slightly richer then I think it will be perfect because the color of the plug before was barely tan, but a little too light for comfort. I would want it to be a darker tan to avoid a potential lean seizure at high rpm.

Without your excellent advice I would have never imagined the adjustment would be that way. After I run it I will post back the results.

Thank you very much!
Alex
 

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Discussion Starter #4
Update- Running great

After performing the high speed fuel enrichment adjustment 30yeartech recommended the Green Machine runs like a winner. The plug is coloring light tan like it should. Looks like the muffler mod was worth it. It now revs much higher than stock and the throttle response is excellent.

30yeartech - Thank you very much for the advice.

Alex
 
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