Originally Posted by TimBucTwo

The only other thing it could be is that #4 is to open and needs to be closed down to see a vacuum reading. When syncing the carbs, is the idle turned down to about 1,000 rpm?

Originally Posted by slowpoke

I believe my 90' is the same carb as your 92'. I have my carbs off as I am lapping the valves. I have 66K miles and thought it would be easy. Anyway, here is a picture of the capped sync port on my carb #4. It appears to come from a large hole above the throttle plate, on the engine side of the throttle plate. I think it is virtually impossible to clog it. Also notice that I put red nail polish (ha ha, it's my wife's) on the sync screws as they are impossible to see with the tank up and the engine running.


Can you try one last thing for me? With your bike on the sidestand and the right side cover off, anyone with a screwdriver, long fingernail, pocket knife, or thin coin is going to try and tighten the mixture screw on carb #4. Here's a picture of it. Just begs to be tightened.


Try and screw the screw in lightly until it bottoms. I think it already is. Then turn it counterclockwise 2 and 1/2 turns out. Then start your engine and see if you have vacuum on the sync port.