Seem to have troubles balancing #4 TB. All the rest respond well to adjustments and are balanced. #4 doesn't change much, which would usually indicate an air leak, yet I have been quite careful to troubleshoot it, and don't find a leak anywhere with carb cleaner sprayed around the typical rubbers. Crankcase vent tube is new and in good condition. Not sure what is next. The plug is a little lean looking when reading it, which indicates an air leak, but where? Ideas, gents?

heres a thought clubie ....number 4 is the closest to the crancase breather, maybe it would be a good idea to undo the jet and clean it out (oily residue from crankcase ) ...im thinking after seeing twbs throttle bodies and the accumulated gunk at the bottom of the jets this maybe has happened to you ? undo the adjuster all the way and get the carbi cleaner in there ...

it maybe hard to dislodge it all as the venturi inlet starts a bit up the body of the tb on the open side of the butterfly ...

second thought is ....butterfly pinion bushes ...i think we have seen some cases of movement/wear in the bushes and this might be enough to leak air at idle and slightly above .

of corse that is assuming that you have done the tb rubbers above and below the tbs already and you dont have a leak / crack in the vacume line to the fpr

ten cents from an aussie

At idle it only takes the smallest bit of extra air to upset the ballance. It could be a small leak from an O Ring under the the spigot the TBs fit on which is individual to each TB.

Or a wasted vacuum line between the TB and the FPR?

I'm using a TwinMax TB balancer, and connecting directly to the vacuum port, eliminating the FPR from the equation for this portion of things. It gets hooked back up after being balanced. I've had these lower TB mounts off a few too many times chasing leaks, and finally replaced them. It is possible the leak is coming from the base of the mount, at the head, but I want to rule out anything else before going there (again). Usually the carb cleaner trick gives you a hint. I've checked the butterfly bushings with the carb cleaner, no change.

did you unscrew the adjuster all the way out clubbie ? first screw it all the way in and count the turns ...the gunk builds up at the base of the needle ....at the jet

No I didn't. I'll try that next. Thx.