First disassembly/cleaning of Bing Type I CVs in 45K.

[frascati]

First disassembly/cleaning of Bing Type I CVs in 45K.

Reason... Left carb can't keep up with right carb vacuum on the manometer under any tuning conditions. I've eliminated (I believe) any source of possible vacuum leaks.

Test rides resulted in rough running, slow to return to idle, and idle revving to 4K rpm at stop lights. Had to bump the clutch to get idle return to normal.

I recently removed the emissions tubes from filter box to cylinders. Plugged the vacuum line in the box that leads to the T between carbs. Plugged the holes left by the tubes removed from box itself. Plugged the cylinders with pair of crankcase drain bolts using high temp Loctite. But doing all this had no effect before/after regarding the above-said symptoms.

Carbs are dismantled on the kitchen table presently.

First.. what do these symptoms suggest? Sticking slide?
And.. anyone off hand know the exact dimensions of the O-rings within so that I can grab some pairs of nitrile or viton at the parts store? Other gaskets in the carb are less than a year old and are fine. The rubber diaphrams appear to be in excellent condition and will remain.

Lastly.. the 15mm "bungs" at the top of both carbs are rattling and loose. ??? I've read online that these ought to be sealed tight. Makes sense. Water could get in. Visual close inspection inside both "domes", under these bungs, there is a loose piece of what looks like a round black rubber flake loosely moving around. About the same diameter as the bung and won't shake out. Ought to just grab it/them with tweezers but was reluctant until I asked here. Suspect it's simply the sealant that used to retain the bungs that has separated and is drifting about in there. So... remove this rubber 'chit' and seal the bungs? Epoxy them from the outside? Jb weld?

The carbs are practically spotless within. I'm not going to have them parts-washed/dipped. I intend to draw carb cleaner through passages using a shop vac in reverse of their natural aspiration. This method has done me very well in the past on many other carbs.

Thanks for any input here

 

[20774]

Just for the record, can you provide the model/year bike and carb numbers? Doesn't really help with this but might help someone in the future if they have the same combo.

As for the "bungs", I've heard of them getting loose...the parts listing doesn't show them as a separate part...they should be swagged in. I'd find some clear epoxy and close the seal around the edge. I've seen some people find roundels of the appropriate size and glue them to the top of the carb.

How far did you disassemble the carb? Did you take the butterflies off to replace the O-rings? Did you get the butterflies back on properly? That can create idle problems.

Nominally, after a carb overhaul, the carbs will need to be synched. That entails setting the carbs to initial book settings, then going for a 15-20 minute ride. When back in your driveway, use fans to blow on the engine while you run through the steps to get mixture, idle speed, and cable tension the same. With your high idle, be sure that the throttle cable ferrule at the carb end is not getting hung up...that could cause a high idle.

But, if you bumped the clutch in order to get the idle to return, that suggests to me that it might not be the carb. Could be that your advance unit weights are sticking out and not returning to normal pulled in position. Could be that it's dirty. Could be that the return springs are shot.

I don't know the dimensions of the O-rings, etc. I usually buy my overhaul kits from Bing...even the dealer has the parts, typically they can be even cheaper than Bing.

 

[james.a]

A sticking mechanical advance unit in the ignition can also cause a high idle, if your bike is so equipped. I helped a young fellow at the Des Moines rally who was convinced that he had carburetor problems. It turned out that the exhaust valves had zero clearance at the tappets. He had been adjusting his idle screws to compensate and when the valve clearance was set right, he had a run away idle setting. Bottom line is; do all the adjustments necessary to establish a base line before doing the carburetors.