when the going gets tough, the tough clean their carbs

[Iahawk]

watched my Iowa Hawkeye mens basketball team lose their first round game last night to Auburn....so to work off my frustration I pulled my carb from my S200 (it was on my to do list before riding season).

There is something very satisfying to me in disassembling a carb in prep for a thorough cleaning. Of course my pilot jet was clogged...for the 22nd time. Planning on spraying all the passages with carb cleaner and also soaking the whole unit in carb cleaner (belt and suspenders?). This is the price I pay for putting very few miles on a bike with a carb.

I will be replacing 2 parts (circled in red in the pic). The o ring for the air fuel screw is kind of boogered up and the diaphragm that is on the upper side of the carb, and attached to a vacuum line has a pretty good pinch in it. Both are cheap so will be replaced.

I'll admit I have no idea what the diaphragm (about the size of a US quarter) does on the carb. Can anyone fill me in?

[NorWeWa]

Video of how a CV carb works. 

Art

[Iahawk]

NorWeWa, good video on a CV carb but it doesn't address the part in question. On mine there is a US quarter sized diaphragm covered by a metal cover with a spring underneath. I've circled the diaphragm, cover and spot on carb where it goes. It's attached to a vacuum line. The diaphragm has a needle that pushes (horizontally) on a plastic spring loaded ball, that opens a passage to the top area of the carb.

In normal use it appears the diaphragm pushes this ball open. When enough engine vacuum is applied it appears to pull out on the diaphragm, closing off the passage. Again, just curious about what exactly this does.

[Ruffus]

hawk, just see this diaphragm as an oscillating part of a fuel pump. Your vacuum line is sucking/ leaving this part up and down to funnel fuel.

[Iahawk]

Ruffus, yes, thank you...an accelerator pump, of course!