Topic: Priming a vacuum operated carburator

[eigenvector]

Seems like I struggle with this every single time I rebuild an old bike with a vacuum operated carburetor. 

Clean it out, carb is nice and dry ready for fresh fuel.  Except I hook up the fuel line, turn on the gas, and spend about 2 days trying to get fuel to flow into the carbs.  Like there's some massive air bubble that has to be displaced before fuel will flow naturally.

I guess I liken it to priming the pump, but in general, is there a good method to get fuel flowing into the carburators when they're dry - aside from turning the engine over to provide the vacuum they need?

I even have this problem when working with remote fuel sources - the kind that don't need vacuum to operate.  Like I say - its like the carb has a giant air bubble in it and nothing will flow until it's gone.

[Steve_K]

Older Suzuki and Kawi models have a prime position on the fuel tap.  Without using prime on dry carbs, like my GIXXER, it takes a lot of cranking to fill the carbs.  The value uses engine vacuum to let the fuel flow to the carb.
Remember after filling carb turn back to run or reserve position of the fuel tap.
Steve

[ekpent]

+1 on most bikes having a prime function.  Do you have a slave fuel tank ?  I made one from a riding lawn mower tank that hangs in a frame and use it all the time when working on new to me bikes. One of those should work well to fill the bowls with fuel also.

[eigenvector]

I do use a remote fuel tank when working on a bike.  Saves the trouble of fiddling with the gas tank if the carb isn't dialed in yet.

Maybe it's the carbs themselves, but priming them really does suck.  Something that I wondered is whether using ether would also facilitate the priming - it at least gets the engine turning and provides the vacuum that it needs.

[Alan F.]

I wonder if attaching a vacuum pump to the vacuum sync ports would do the trick?
you could run some Y connectors to get all cylinders connected and pull some vacuum for several minutes then give the float bowl drains a check....  May have to set engine rotation so all exhaust valves are closed.

Thoughts?