ch150 carburetor question

[scottorious]

I just acquired a kind of basket case ch150 and I want to build a skelly out of it. I am in the process of rebuilding the carburetor and this model has an air cut-off valve. I didnt get the valve while it was put together so I am not sure if there are internals that I am missing. Is anyone familiar with that? The parts view only shows the entire valve and the service manual doesnt mention anything about whats inside the valve body.

[Wheelman-111]

Greetings:

The similar CV-40 was stock on every recent Harley-Davidson before EFI, so I know it pretty well. I actually adapted a Constant Velocity VE-24 carb to Flash II for a while. Aside from the cabling nightmare it ran pretty well. The cable attaches to a snail that opens the butterfly valve, but the real "Throttle" is the slide/needle which is controlled by vacuum that raises it via a Diaphragm.

Aye, there's the rub. You need extra fingers on each hand to screw the diaphragm Perfectly down into its groove under the cover. And the diaphragm fights every step of the way to pop out somewhere, particularly if the carb is older and the rubber has been exposed to gas fumes for a long time. One trick is to freeze the valve/diaphragm assembly. This makes it stiffer and dries out the absorbed fuel so it fits better.

However it's really easy to get it wrong, and the slightest gap in the sealing surfaces will make a carb that starts and idles but refuses to go for a ride. Same goes for a diaphragm with even the tiniest hole or crack. Replacement slide/diaphragm units cost more than whole cheap carb.

Otherwise, the carb is fairly simple and once correctly assembled it's very reliable.