Revs great in neutral, flops and dies under load?

hi guys,
its a '77 kz650B, just chem-dipped and rebuild carbs with all new jets, everything stock setting. dyna ignition and coils new top end gaskets, rings, honed (not bored) the cylinders, lapped and adjusted the valves, uni pods, stock exhaust

so after the rebuild it ran great on the lift, and i was excited. it starts on the first kick and revs right up (as high as i dared while the rings seated). When i went to take it around the block, it bogs way down and sometimes dies as soon as the trans starts to engage, it is not so pronounced while rolling, but still noticable, and there is very little power.

I hope that this is a carb problem, because I feel ok about working on them (as opposed to the trans). I am at about 5000 ft. and like I said, i put the carbs back to factory settings. Is it better to adjust the pilot jet, the needle or both? Does this sound like something that a good carb tune could solve?
thanks

If not already done, would use strobe-type timing light to assure correct ignition timing, and especially to confirm proper operation of the advancer unit.

With advancer stuck closed, unloaded engine will rev seemingly okay.

Also, what do the plugs look like -- did they quickly soot up? If excessively rich mixture, could be problem in carb pilot circuit.

Do pilot screw adjustments have any effect? If not, also points to pilot circuit.

The air/fuel mixture in the pilot circuit is not correct... typically at 5K feet, it will be rich due to the thin air. Adjust the pilot mixture screws to fix the issue.

thats exactly what I wanted to hear WG. it looks like you are quite the carb guru around here, i will try this the first chance i get. thanks, aj

by the way, the mixture screw is on the airbox side, so it is an "air screw" right? which means i should adjust it out (not in) to allow more air into the mixture? or do i have it backwards?

Post edited by: ajohnson, at: 2007/09/24 15:23

Turn out the air screws to lean the mixture.