hey folks,
trying to fix my /5 but am having trouble with the carbs. I’m used to Japanese bikes and these are a bit different. I had no good top end performance and the left cylinder was running rich. I could smell gas on the plug. I noticed fuel leaking from the throttle shaft so decided to rebuild. All going ok until I tried to remove the shaft. I couldn’t get those two screws loose on the valve. Folks on Facebook said to grind down the back sides because it’s crimped but they still won’t budge. Now the head is starting to strip and I’m afraid that if I keep trying it will strip completely. I’ve used plenty of PB blaster with no movement. How do I get these screws out?? I’m almost to the point of replacing the carbs with Mikunis! Many thanks!
Stop ! I have rebuilt dozens of Bings without ever having to remove those 2 screws.
If fuel is coming out that shaft, then removing the shaft is NOT the solution !! Your float levels are obstructed, which is allowing the fuel level to rise far too high. The normal fuel level is about 1/4" BELOW the rim of the float bowl. IOW, the fuel level is about 1/2" higher than it should ever be.
A carb float system works exactly like a toilet. If the float is obstructed, then water may overflow the water tank. But we don't disassemble the flush handle !! Instead we fix the float, because just like a carb, the normal fluid level is well BELOW the top of the tank.
> Order 2 new Bing floats and 2 new Bing float needles. Your root issue is most likely that the internal parts have never been updated to the newer "ethanol-proof" parts, which have been available for several decades. This is the problem with older bikes taken out of long-time storage. You've got to remember that the original Bing parts were designed for 1970's leaded fuels. These older fuels have not been available since ~1990. Modern ethanol fuels are MUCH MORE destructive.
> This is just the "tip of the iceberg". All the other "rubber" parts in and around the fuel system will also need to be updated because of the very deleterious effects of ethanol and general aging.... both carb mounting hoses, all O-rings, all fuel hoses, the packing inside the petcocks... just to name a few. (All fuel hoses should be marked "SAE J30" so that you know they are ethanol proof.)
> And while you have the credit card out, it would also be a good idea to check the condition of any hoses used in the engine breather system, which are found under the Starter Cover on top of the engine and inside the air filter housing.
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Early Bing carburetors are considered to be wonky.
https://bmwmotorcycletech.info/earlybingR75CV.htm
former Airmarshal, IL.
@wobbly Thanks for the information. I'll change that out. Any idea how to get these screw out? I take it that the leaking shaft is a problem right?
@wobbly Also, should I just send these off to have them rebuilt? I've rebuilt many Mikuni's and Webers, but these are quite different in my opinion. Could the floats be bad even if they don't have any gas inside of them? And what do you think about switching to Mikuni's? It's cheaper than having Bing rebuild these.
@wobbly Thanks for the information. Any idea how to get these screw out? I take it that the leaking shaft is a problem right?
Did you even bother to read what I wrote ?
The fluid level should be 1/2 to 3/4 inches BELOW the level of the butterfly shafts. IOW the gasoline should NEVER be anywhere near that high. The problem is NOT the shafts or the O-rings on the shafts. The problem is the float system is not stopping the fuel at the correct level, which is much lower.
If fuel is coming out your throttle shafts, then fuel is also flooding down your intake port, and diluting your engine oil. Don't worry about your carbs. Your engine will soon throw a rod through the side of your crankcase.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
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