Bike was at a reputable mechanic for maintenance - carbs were overhauled and overall bike runs well - I did some online searches and read fuel leaking on left carb (side stand side) can leak if fuel not turned off @ 1/4 mile from final destination. The petcock valves were replaced as well as the floats but the float needles seem to be original. Is there any difference between the two float needles shown in images below? Also, what model Bing is on a 1973 R75/5? I'm guessing a carb mate cannot be connected to a carb this old - the mixture seems a bit rich as it is runs a little rough a mid RPMS but idles great and runs great at higher revs. Thanks much.
Ken
• In my experience, earlier float needles were all metal. Since the introduction of Bing's "ethanol kit", the float seat end has been wearing a synthetic Viton tip. These later ones are a much better design, much more tolerant of grit, and much less dependent upon float seat condition.
• The requirement to turn OFF your fuel is not caused by the float needle, float seat condition, or anything to do with the pet cock. Ever since 1679 when Sir Issac Newton discovered Gravity, gasoline has wanted to flow downhill. Therefore, on any vehicle, lawn mower or any other power equipment where the fuel tank is above the carburetor, Gravity wants to force fuel to travel from the gas tank and end up in the engine's sump. If the sump is full of engine oil, as it is on the Airhead, then that oil will be diluted and highly compromised. If the sump is empty, as on an older British motorcycle, then it will typically be unceremoniously puked out through the sump breather.
I have done a thorough search and can find no evidence of Airheads having this issue before 1679, so it must be Newton's fault. 🤣
• Bottom Line: If you want to keep fuel out of your sump, then replace the float needle with the latest version AND replace your 50 year-old pet cock packing. Then be rigorous in turning your fuel taps OFF when (or sightly before) you stop your engine.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Shut off the bike, shut off the fuel, park it … it becomes a habit. I slip up more with remembering to turn it back on again, and start running out of gas in a half mile. Dummy! Yes, update to the newer needle valves.
I don’t know how to share a link here, so; Go to bingcarburetor.com, then select “motorcycle cv - type 64 & 94”, then go to the bottom of the page and download the “BMW_Jetting_Chart” in the very bottom, RH corner. The chart gives you carb numbers by model, and all stock jetting info.
https://bingcarburetor.com/uploads/9/8/7/9/98794296/bmw_jetting_chart_cv_carbs.pdf
[Mods added link]
SnowBum has an article on everything you ever wanted to know about Bing floats and then some. Carb tuning/trouble shooting starts with being sure the float/float needle maintains the correct fuel level in the carburetor. bowl.
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