I have a regular one input vacuum gauge. It doesn't seem to work because of the dual carbs. Anyone know where I can get one that will work? Is there a way to make the single input one work?
thanks.

 

I would try my trusted dealer first and also ask him about a service manual too.

Do you think the carbs are possibly out of sync on your machine?

 

Got the shop manual. No, I just like to make sure everything is correct. Does carb sync affect wide open throttle performance or only light throttle performance?
Thanks.

 

In my experience with road bikes, and other engines with one barrel per cylinder, the carb balance did not affect mid throttle to wide open throttle (unless they are really really far off).

The 650 does not sound quite as smooth as some engine because it is not even firing. It is primarily in balance, which is why it does not shake like a one cyl or the polaris 700, but that design makes the time between cylinder firings uneven. Sometimes when I haven't shaken the cobwebs out of my head, that 650 twin rumble plays tricks on my ears.

 

I seen some in jc whitney for about $45. They were for 4 cylinders but would work on a two cylinder.
Un-sinc carbs can be very funny. I don't believe top speed would be affected unless you were pretty far out.
Carberator vaccum can be an excelent trouble shooting tool thow.

 

Take a look at Motion Pro. I'm pretty sure they have one.
Mark