Motorcycle Repair: cb500t seems to be missing above 4500rpm, pod air filters, point gap

Question
I have a 1975 cb500t dohc rebuilt top end. Bike starts fine
runs fine until it hits 4500-5000rpm, then it refuses to run
smoothly, it appears to spit, putter, and misfire. if i
persist and hold throttle mid way to 70% open for about 8-12
seconds of this erratic running it will then spring into
life and runs great until i pull up at lights or slow down.
any help would be appreciated

Answer
Jamie... check compression first, after adjusting the valves, so we have a baseline to work from. Hopefully, the camtiming is all set correctly, as that can cause performance issues if you are off one tooth on either camshaft setting.

Beyond that I would check the spark advancer for proper function ..advance/retard, and recheck the spark timing again. Be sure that each set of points is open/closed separately from the other. If point gap is too small, where both sets of points are closed at the same time, then the coil saturation current draw of both coils will drop the overall voltage potential of each one. So, be sure that the point gap is out about .016" (.04mm?) and each set of points open at the F and LF marks respectively. Primary coil winding resistance should be 4.5 ohms. Spark plug caps should be 5k ohms. Watch the ignition points for excessive arcing, with engine running, indicating a poor condenser connection or weak condenser, itself.

Verify fuel flow through the petcock and obviously through cleaned carburetors, jetted for any modifications such as pod air filters and modified exhaust pipes.

Check the gas cap for a plugged vent hole.

Bill Silver