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TB Sync and air mixture idle screws


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I did a TB yesterday. Off idle, the bike is running great. At idle, not so much. I pulled both of the big brass screws and there was a lot of carbon buildup on them, especially the right-hand side. I cleaned them out and cleaned the seat. I can't get a good look down the right-hand seat, but I suspect that the port at bottom may still be blocked.


When I did the sync at idle, I had to turn the left-hand idle screw almost all the way in. The right-hand screw is at 2 turns out. Screwing the right-hand screw all the way in doesn't seem to do anything.


The bike idles OK, but a bit rough and slow when warmed up. It smokes and won't idle at all when cold. I back the left-hand idle screw back out to 2 turns and it idles OK, but not great. Obviously this throws out the sync at idle.


So the question is, do you think the port at the bottom of the right-hand idle screw is blocked? Can it be be cleared without removing the TB?

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Glen, it does sound like that side is plugged.. You can usually clean the BBS seat using spray carburetor cleaner & if really plugged some compressed air..


Watch the paint on your motorcycle as carb cleaner is a great paint remover.. Also if possible try & find some 02 sensor safe carburetor cleaner..



If that BBS seat is really coked up you might need to run a SOFT wire into it while using the carb cleaner.. A copper wire strand from a heavy lamp cord will sometimes work (nothing read hard or sharp)..




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I got the port cleared with a small wire. The engine now responds to right side screw adjustments.

Looks like I need to do this at my next TB balance. The engine runs just fine, but left is ~1.5 and right is ~.5. I remove the brass screws and clean each time, but more drastic actions may be needed.

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My screws are pretty much evenly matched. I can now control idle speed by making the same correction on both sides, while maintaining balance, which I could not do before.

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