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Bing CV Carburetors, Part 2
© Copyright, 2014, R. Fleischer
A basic MINI-overhaul can be done with the carburetors in place on the engine. This is often quite enough. Two articles, the one you are reading, AND http://bmwmotorcycletech.info/bingcv.htm are not just about how to overhaul a Bing CV carburetor. These two articles are specifically designed to fully inform you what you need to know, as an Airhead owner/rider, about these carburetors.
The one exception is if you have an R75/5, which came with a particularly troublesome version of the Bing CV carburetor. For those R75/5 carburetors, you should review the above linked articles; AND, in particular, review http://bmwmotorcycletech.info/earlybingR75CV.htm
1. Starting problems:
It was in November of 1971 that BMW first ...and almost lastly....recommended OPENING the throttle during cold or very cold starts. We all know that this can be a necessity depending on the bike, temperature (does NOT have to be very cold), & how the carburetors are adjusted. That is still true for later models, but BMW has dropped the recommendation of an opening throttle. SHAME. While SOME Airheads will start OK with throttle shut off and enrichener turned on or fully on, many need a bit of throttle playing AS THE ENGINE BEGINS TO START.
If your Airhead starts OK, enrichener (choke) in use, ....then seems to run out of fuel, after perhaps 15-30 seconds: