First off, buying cheap from an ebay vendor is a crapshoot. The carbs come from the factory with "generic" jetting, and to tune a VM carburetor for the XS650 you'll need to change every bit of brass in it except the slide, and some tuners change that as well. Then there's the possibility that you'll wind up with a substandard knockoff carburetor or substandard knockoff jets. If your engine hasn't been modified for performance, you might consider the VM32. You can use the stock carb boots on your '83 with VM32 or VM34 carbs: the spigot is a little smaller than the BS34, but you can get a good seal if you replace the OE clamps with good hose clamps. If you think you might need tech support, there are only two vendors I'd recommend: Michael Morse of 650 Central and Gary Hoos of Hoos Racing. Both of these guys are pro tuners, answer their own phones, and return phone calls. Tip: it pays to do your homework before you buy the parts. The Tech menu will give you a lot, and a few searches will show you what kind of snags others have hit so that you can avoid them.
