Mikuni - Uneven vacuum on single bore

[byunique]

I have 3 x 44 Mikunis, and recently noticed that one of the bores on one of the carbs has lower a lower vacuum reading compared to rest of the bores. This is taken with a Synchrometer which is very consistent/accurate. This one bore measures a vacuum level of "3" compared to "5" on the rest of the bores at idle. I have since moved the carbs around to isolate whether its a carb problem or not, and the problem goes with the carb as I swap the carbs around. I have since pulled the carb out, dis-assembled everything, blown everything out with compressed air, checked the jets etc. I have also swapped the position of the jets, and top cover (including floats) to see whether I had a clogged jet or something, but nothing has changed for the better.

The only thing I can think of is the throttle plate is not consistent in terms of clearances from bore to bore. As far as I can visibly tell, they pretty much look the same, and consistent in terms of where you can see the light come through. Chokes, auxilary venturi, position/seating looks good too.

Any other ideas guys?

[jmortensen]

Twisted throttle plate, so one butterfly is slightly more open than the other when they should both be closed. It's not really too big a deal and you could just leave it alone, but there was some discussion about twisting the shaft via the flat section on the ends of the shaft, and some warning about how badly you could screw it up too. It came up not too long ago, maybe a couple months back. Search and you'll find it.