/9 /10 Bing 32mm Carbs - Super High idle after warmup

[jjwithers]

I have a few questions here...
These are the 32mm /9 and /10 carbs. In hindsight, i probably should have bought a set of newer, 32mm carbs from a /7 instead of re-using the /5 32mm carbs. Anyhow...

First, i am having a difficult time getting a low, balanced idle on my latest /5 build. Everything has been rebuilt (engine, carbs, entire bike, Dyna Ignition added, Custom exhaust, etc..) and I fired the bike up this weekend for the first time.

The throttle plates make a nice seal inside the carb. the choke is off. Timing is OK (last I checked).
I went for a 'break-in' ride and came back and adjusted the carbs. It would idle a bit too high.
I am told that the hole in this photo is too big and creates a leak of sorts so the choke is always goofy (photo taken before i rebuilt and cleaned carbs):

Is there a way to fix or modify that hole to make it smaller?

Next question....
After that ride and cool down, the valves have been re-adjusted and the heads re-torqued. Still an iffy idle (too high and not balanced).
I took it for a 20 mile freeway ride today and at the end of the ride, the idle was super high (3k-4k rpm).
I let the bike cool, started it up, and the idle was low again (but back to being slightly too high).

What would cause the idle to get so high after then engine is hot like that?

Thanks in advance...
The excitement of my restoration being back on the road is halted because of all this.
-josh

[Ken in Oklahoma]

I have a few questions here...
These are the 32mm /9 and /10 carbs. In hindsight, i probably should have bought a set of newer, 32mm carbs from a /7 instead of re-using the /5 32mm carbs. Anyhow...

First, i am having a difficult time getting a low, balanced idle on my latest /5 build. Everything has been rebuilt (engine, carbs, entire bike, Dyna Ignition added, Custom exhaust, etc..) and I fired the bike up this weekend for the first time.

The throttle plates make a nice seal inside the carb. the choke is off. Timing is OK (last I checked).
I went for a 'break-in' ride and came back and adjusted the carbs. It would idle a bit too high.
I am told that the hole in this photo is too big and creates a leak of sorts so the choke is always goofy (photo taken before i rebuilt and cleaned carbs):

Is there a way to fix or modify that hole to make it smaller?

Next question....
After that ride and cool down, the valves have been re-adjusted and the heads re-torqued. Still an iffy idle (too high and not balanced).
I took it for a 20 mile freeway ride today and at the end of the ride, the idle was super high (3k-4k rpm).
I let the bike cool, started it up, and the idle was low again (but back to being slightly too high).

What would cause the idle to get so high after then engine is hot like that?

I doubt your fast idle when warm problem has to do with your enricher assembly. More likely the springs on your advance weights are weak and need to be changed. When the engine is cool the idle is slow. But as it warms the engine tends to idle slightly faster. But if your advance springs are weak the weights may go out prematurely which advances the timing which speeds up the engine.

Here's something you can try. With the engine warm and the problem happening, shut off the ignition for a second, letting the engine slow toward a stop. Just before the engine stops switch the engine on again. If the engine doesn't speed up that would point to your advance springs.

Another thing you could do would be to set your idle to a slower rpm, say 100 rpm slower. That way you have a bit more "head room" before the advance weights start advancing.


Ken

[jjwithers]

Great tip!
I actually put tighter advance springs on the advance mechanism already. I didn't think it mattered with the Dyna Ignition but a mechanic I was working with last weekend recommended it. They are still 'used' springs but they are still fairly tight. maybe they got stuck? Maybe it needs lubricant?

That wouldn't solve the low idle issue though...

[Duane Ausherman]

Just make the test that Ken suggested.

[daz]

Good evening JJwithers. Did you do the test that Ken suggested and what happened?

[Kurt in S.A.]

That hole seems OK as compared to these photos:

http://www.pt-photos.com/carb_page.htm

Kurt in S.A.

[jjwithers]

The bike was out of commission since i started this thread. I recently got it running again with a new set of carbs and it runs great. I only put about 15 miles on it since the really high idle incident but so far, it has not happened again.

I'll post back with any findings as i continue to break this new bike in.

Good evening JJwithers. Did you do the test that Ken suggested and what happened?