Carbs keep overflowing R60/2

[davidmcctan]

Hi guys,
Changed the float cover, needles , and floats and completely cleaned the carb meticulously. Bike runs fine but when I shut the engine off, the carbs start a drip drip drip ,until I turn off the fuel clock.

Is this normal to the BMW family?

Also, I noticed that if I turned off the fuel clock while the bike was running, the rpms jumped up right away (instantly).

On my other bikes (moto & honda), it usually only jumps up after the carbs start to empty

Any help appreciated..

[Slash2]

1. Are we to assume that it wasn’t leaking before your recent carb service? If so, I would guess your problem is there.

2. You say the bike runs fine. What does that mean? Does it run properly across the RPM range with even steady power? Quick, easy starting? Are you riding or just idling in the garage?

3. Does it drip for a few minutes and stop or would it drip all night?

4. Is the bike on the side or center stand?

These bikes and most old Bing carbs are somewhat notorious for a drip on shutdown. Some guys will close the fuel valve down the block to prevent this or allow the bike to run out of gas while idling before parking. I personally find that my bikes only drip when left on the side stand, but never drip while on the center stand provided the carbs are properly adjusted.

Of course needle height, float weight and positioning etc directly effect fuel flow.

The fact that your RPM’s are increasing when you close the valve indicates to me that your needle position or float is likely causing the bike to get too much fuel causing it to run rich. So, when you close the valve, the reduced fuel supply allows the mixture to lean out and your carbs to function properly.

Pull and check your plugs to verify this. If they’re black and wet looking, I would revert my last modification by restoring the carbs if possible or verify that your replacement parts are not only correct, but correctly fitted.

5. One final thought. You mentioned the float cover. Again I’m making assumptions but did you replace old style tops with newer lever tops? If so, did you verify compatibility of the needles, floats, etc? It’s been years but I recall having an incompatibility issue with lever tops, Vechs plastic floats and stock needles. It seemed the small disc spacer required some adjustment but my memory isn’t crystal on just what it took. I can open them up to see how they’re setup tomorrow. Come to think if it, I do believe that the lever tops require a rubber tipped needle in order to fully seat. In saying that you changed the needles and floats I’ll assume they’re correct and if so, that would suggest that your float is either incorrectly installed or faulty, (leaking if copper) or the needles may be upside down or have some other adjustment issue.

6. Now.. is it only leaking on one side or both? If both and your carbs are in fact set up properly, are you currently tuning your bike on an auxiliary fuel tank suspended higher than stock tank height? I can’t imagine why you’d be doing this but it’s worth the mention. Okay I’m out of ideas until you provide some new information.

Good luck.


Chris

[Jim D 5112]

Most older motorcycle carbs are not capable of holding the fuel back with the gas valve left on that is why most owners manuals tell you to turn it off when stopped. My friend spend a lot of time on his carb that would leak a little bit even with the fuel shut off. It turned out that although the fuel valve was shut it was still letting some gas by. Fixed the valve and took care of the carb leaking. So his carb could not hold back even a small amount of gas from the leaking valve. So if you stop the bike and turn off the fuel there is still fuel in the lines that may flood the carb and leak out. These old carbs were never perfect and some just don't shut the gas off as well as we would like.

[davidmcctan]

Just updates

Carbs were dripping even before
Bike runs fine at idle, freeway, WOT
Carbs Drips for bit then stops
Never paid attention to what stand , but most of the time it is on center
The float covers are NOT the lever kind, they have the little metal push button..

I think and agree that this is really the nature of the bing carb...drip, drip , drp

Interesting to find out if the lever tops and needles that have the rubber tips actually stop the drip..


Anyway..stay safe guys

[schrader7032]

IMO I don't think that's the nature of Bing carbs. Mine rarely drip.

[FL54]

+1

[Daves79x]

Where exactly are the carbs dripping from? Is it from the mixture screw threads on the side? That screw is also the bowl vent, so an over full bowl will naturally drip there, and also a normal bowl level will drip there if on the sidestand. Other problem areas are the threaded caps on the bottom. Thread sealing compound will slow the drips there, but be aware that some loosen over time and drip. The bowl tops often warp from over-tightening and sloshed gas leaks there too. You have to identify exactly where the leaks all are to diagnose what to fix.

Dave

[fogg6928]

I have a 1960 R60 with the original non lever top carbs. I don't ride it as often as I should and I started getting carb overflowing problems. I believe a large part of the problem could be fuel drying up in the socket in the bottom of the float bowl that guides the float needle rod. The float needle sticks in the socket and causes the carbs to overflow. Try cleaning the little socket and see it that helps. It did for me.

I have only had my R60 for about 18 years, but I really like it. (I have had my R69S for 50 years.) It is easy to start, runs smoothly, and is just a great bike.

[dosgatos]

Bing incontinence.

[jwonder]

+1 for Bing incontinence. The upgraded "lever tops" had better needle valves which made this happen less, but they still do it from time to time. I always turn my fuel off before I turn the engine off. I let the engine idle for at least 5 seconds with the fuel off before pulling the key.

http://bingcarburetor.com/early-bmw.html