kz 750 rpm problem, carbs? or ignition

i was on this problem awhile back but i couldn't find the old thread.
so this is the deal, this bike - new oem size piston rings, new mac exhaust, rebuilt and rebuilt carbs. it cranks up real good and idles good, but it only revs up to about 3500 rpm then it starts crapping out like it's starving for gas. we came to the conclusion that it was somthing in my ignition system, i was running a little rich, (which seemed ironic), i bought a new accel coil, that seemed to lean me out, and now my spark plugs look good, but, like an idiot, i screwed with my carbs and i don't know where the pilot screws where at (#of turns) and i still can't get over 4ooo rpm!!!!! i did the static ignition timing very close, and i did all the points gap stuff with feeler gauge and all that good stuff. sorry this is so long

Post edited by: cratgo, at: 2006/07/10 03:33

If you set the timing, then you must have a strobe-type timing light. Remove your points cover and observe the mechanical timing advance when you rev the engine to 4K rpm. Does it advance cleanly? If not, remove the advance from the bike and take off the center part. Clean with steel wool or something similar and then lubricate.

If your bike feels like it is starving for fuel, it may have some vacuum lock. The effect is, fuel can't be pulled through the fuel system. A normal culprit is that the gas cap has plugged venting. Next time you start the bike and rev it, do it with the gas cap open.

Last, check the routing of your gas hose to ensure it isn't pinched or kinked. This will also cause the problems you describe. If you have a fuel filter, change it. You might even want to remove your petcock and examine the screen on the inside of the tank that covers the pickup tubes. If there is any stuff on the screen, it may be partially obstructing gas flow.

ERRR another Last... (just thought of this)... you engine probably doesn't rev as high as an inline four? 4k rpm lid may mean jetting is off. If you have added pods/pipes to this bike, did you rejet? The secondary mains may be too small and restricting the bike from pulling more rpms.

Post edited by: wiredgeorge, at: 2006/07/10 09:11