was syncing my carbs on a 97 m750, and i was only able to get a max draw of 8 psi from the horiz cyl, where i was getting between 12-14 on the horiz cylinder. i spent quite a while at it, going back and forth, and was only able to get that 8 on the horiz in one specific spot, a smidge either way and it was down to 6. i was able to drop the idle screw way down from where it was, and it is a lot smoother, however, its still slightly dodgy at low rpm cruise. i sprayed a bunch of carb cleaner to see if i could find a vac leak, but had no success. anyone else with some insight?

There's a balance adjust screw on the throttle shaft that connects the two butterflies.

You can adjust that to get the balance sorted out.

i wasnt checking the sync, i was ACTUALLY syncing the carbs. is there another screw besides the one behind the idle adjustment screw?

Sorry, I misunderstood.

That's the only screw for adjusting balance.

Perhaps one of the slides is sticking.

How are the needle jets and needles?
They wear over time, changing the fuel flow quite a bit.

diagnosed a bit of my miss. had the tach wire from my vapor on the wrong end of the coil, it was robbing power. the bike is pretty new to me but the previous owner had a issue with the float sticking on a carb and draining the tank onto his floor. he went through the carbs at that point, so i suppose they are relatively clean. runs pretty well now, just wondering if there is something someone might know of to cause the vacuum differential.

I've seen an intake manifold that was split, where the rubber is bonded to the aluminum.
Looked OK from 2 feet away.

Quote from: Speeddog on September 22, 2008, 10:28:04 PM
I've seen an intake manifold that was split, where the rubber is bonded to the aluminum.
Looked OK from 2 feet away.

Also, look at the vacuum hoses - I think the horizontal cylinder's inlet manifold has a bleed for the petcock, and the vertical one has a bleed for the fuel pump. If either of the hoses are old and split, or a diaphragm in the pump of petcock (and the pump diaphragms are a kinda "known issue") - that could cause problems like you're describing...

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