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21 Posts
Discussion Starter #1
Thanks to everyone's whelp in the other thread with all the suggestions. It really helped!

So fellows, the carb is all back together and the bike is back online but now there seems to be a new issue.

After syncing the carbs and adjusting the idle screws the carbs don't seem to be closing all the way. The return cable seems to be solid. I ordered new ones for good measure.

I didn't touch the return spring on the carb so idk if that would be it. But maybe.

When I have the bike idling if I push up on the sync adjuster screw between no 1 &2 carbs the idle returns to normal so obviously it's not fully closing and letting to much air through. ??

Any thoughts guys?

ZAMM Fanatic
2,730 Posts
What's the mileage on the bike?

I don't know about bikes but on cars the holes in the carb or throttle body the throttle shaft rides in get worn over time, become oblong instead of round.

Sometimes a stronger spring along with lube will cure the problem. Other times you have to go find a less worn-out or replacement carb.

On lawnmowers the throttle disc itself is often attached to the throttle shaft with two little screws. Sometimes there's a little play and you can adjust it so the disc is better centered in the ...hole. If it's OFF center sometimes it will bind instead of close.

Many carbs leave the disc open a few degrees and have microscopic fuel ports (for idle fueling) right by where the "crack is.

With multiple carbs you may need to release the common shaft return them all to idle then re-tighten.

Wear, lube, adjustment..... stronger spring.... you should be able to get it to where the bike's rideable.

Hope this helps.

Ace Tuner
2,936 Posts
? Need more info?
Yes, tell me how you set the carb sync. (I'm thinking it could be way out of wack).
Do you have some free-play at the twist grip?
Can you see/feel some slack in the cables at the carb's when you touch or push on them by hand?
Does the idle speed adjusting screw have any affect on idle speed when you turn it?

An unlikely possibility would be an air leak. (Usually will not idle at all). But.....
You could have an air leak on the vacuum line that goes to the petcock, or in the petcock itself.
You can eliminate that possibility by unhooking the line and plugging the spigot/vacuum tap on the intake manifold and running with the petcock in the PRI position.
Or there could be an air leak in the vacuum switch for the air injection system.
You can eliminate by unhooking those lines and plugging those spigots on the intake manifolds.
Also, make sure the spigot/vacuum tap that is not use is plugged.

21 Posts
Discussion Starter #6
SemiFast thanks so much for all your help with everything man. You've really been a lifesaver with this thing..

Answers to your questions..
1. Synced it with the vacuum hose carb sync tool. I bench synced it first then.. I vacuum synced it. The blue sync tool one you buy on Amazon for about $80. I set the idle screw high till the needles no longer bounced around then set the 1+2 carbs (1 carb seems to be the one not closing). Then the 3-4 then the middle screw. This is direct from the manual. All carbs were set according to factory spec. I can double check if you advise.

2. Free play in grip is set to factor spec. Although since I brought it out on the road the free play has increased significantly. Red flag .. It's probably 10mm now. So I know it's horrible. But it seems as I try to adjust it just falls right back into the same gap.

3. Yes there's a bit of slack.
4. Idle speed screw controls it. I can stall the bike with it or make the engine go wild. Just so I'm clear I'm talking about the screw on the side of the carb not the pilot adjusters. I'm sure that's what you meant too.

I will have to try out the vacuum tests you recommended. Won't have time tomorrow maybe Wednesday. I order we new cables anyhow for good measure. These cables are factory direct. 23 years old and I feel like maybe I damaged them during the carb rebuild. Hard to tell. Better safe then sorry.

There's a video on my YouTube. Thomythetrainer sorry can't post here I don't have enough posts to post one I guess.
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