Question about CV carbs regarding needles and synching.

[KEITH KRAUSE]

I don't have CV carbs but I would like to know more about them, so I can help others with questions.
My question is, when you change the stock jet needle to an adjustable needle with a jet kit, do you have to re-synch like you must on the VM carbs?

[daveo]

I'm sure it would start and run if they were relatively in sync before you started, however, I find that the syncing is easily disturbed, and very critical to proper performance,so every time I mess with the carbs or even just have them off for something else, I re-sync them, PIA that it is, I just wish they had a finer adjustment, something without a locknut and accompanying thread stretch to compensate for when adjusting.

[Don Lobacz]

You should not have to synch them because the synch is controlled by the butterfly valve, not the central slide that houses the needle.

[nert]

True. The "Act" of synchronizing the carburetors, measures and attempts to "adjust" the negative pressure to "equalize" across multiple carburetors and intake tracks. (pistons, cylinders, and valves ability to pump air). Changing the fuel ratio should have little affect, however the vacuum method of synchronizing is patronizing and can compromise accuracy caused by individual combustion efficiency. Carburetors can be more accurately synched by using a tool to measure the VOLUME of air flow amongst grouped carburetors. We used to use such a tool on many vintage multicarb porche, mg, triumph, volvo, even corvair, and SU type carbureted automobiles. A side benefit of using a single tool is having no calibration between (4) measuring tools. The single tool is used to set all carburetors, thus eliminating transferred/calibration inaccuracy. Getting to basics, an engine is an air pump! The GS has 4 air pumps working together. The act of synchronizing should be; get individual cylinders to pump evenly. Fuel and ignition are ?effecting? factors that should not be considered when adjusting carburetors as they may compromise the act of accurately synchronizing multiple air pumps.

[KEITH KRAUSE]

Thanks for the replies. I did'nt think you had to re-synch CV carbs if you made adjustments to the needle, but I was'nt sure.