Bing 40mm Rotary Choke Valve

[hobbywhore]

I have a Bing question concerning the position of the rotary valve when the choke is on. First, the problem I'm having is one cylinder wants to run rich. Everytime I pull the plug, it's very dark and black, sooty and dry not oily. The bike operates fine, cold or hot, I've never had any trouble starting or riding. I live at sea level (some sections are below) in New Orleans so that eliminates altitude. I rebuilt the carbs when I restored the bike with gaskets and "O" rings and diaphrams and I have been installing leaner and leaner main jets to see if that would help. The other cylinder seems to be doing fine, so now I suspect I might have installed the choke lever on the wrong side of the rotary valve, making it operate backwards (on when I think its off) on that one side. I bought the Bing manual, but there's very little information on the cold start circuit. What I would like to know is what position is correct for the rotary valve when the choke is on? Thanks ahead of time for any help!

[cjack]

I have a Bing question concerning the position of the rotary valve when the choke is on. First, the problem I'm having is one cylinder wants to run rich. Everytime I pull the plug, it's very dark and black, sooty and dry not oily. The bike operates fine, cold or hot, I've never had any trouble starting or riding. I live at sea level (some sections are below) in New Orleans so that eliminates altitude. I rebuilt the carbs when I restored the bike with gaskets and "O" rings and diaphrams and I have been installing leaner and leaner main jets to see if that would help. The other cylinder seems to be doing fine, so now I suspect I might have installed the choke lever on the wrong side of the rotary valve, making it operate backwards (on when I think its off) on that one side. I bought the Bing manual, but there's very little information on the cold start circuit. What I would like to know is what position is correct for the rotary valve when the choke is on? Thanks ahead of time for any help!

It's kind of hard for me to remember, but I do know that the dimple on the choke shaft is nearest the handle that gets pulled on when you operate the choke and all that, including the handle is nearest the intake port on the choke assembly. The intake port is the jutting out island on the square of the choke cover. The handles point to the rear of the bike. You might check that on your carbs. Since it is only one cylinder, then probably you don't have the choke guts mixed up left to right I'm thinking.

[hobbywhore]

Thanks cjack, that helps a lot. I checked out the ckoke levers again according to the information ou gave and they look OK - both pointing the rear of the bike. I've got a spare carb I took apart and have been studying the rotary valve and I think I see which position is "choke on". I may have to go back to the beginning to try to diagnose the rich mixture.

[cjack]

Thanks cjack, that helps a lot. I checked out the ckoke levers again according to the information ou gave and they look OK - both pointing the rear of the bike. I've got a spare carb I took apart and have been studying the rotary valve and I think I see which position is "choke on". I may have to go back to the beginning to try to diagnose the rich mixture.

Also check the dot or dimple on the shaft showing that the handle is screwed down on to see that you don't have the disk turned 180 degrees.

[tghsmith]

make sure the dimple on the end of the choke shaft is on the same side as the bump on the choke cover plate.

[James.A]

A sinking float will produce the effect that you describe. Also, the variable jet (disk) can be fitted heads or tails, like flipping a quarter. However, if the disk is fitted improperly, the bike would be hard to start and run poorly.