I am having the same issue , starts great runs good until aprox 4200 rpm, then limits out,
hit the trim up or down, she starts to rev briefly, some times a quick turn will fix this
and she will run at 7200 rpm up and down all day.
the plugs are a sweet mocha brown , all grey lines have been replaced and the carbs gone thru,
gas, res selector valve cleaned. all filters replaced
this happens everytime it sits for a few minutes or first starting out.


the batt is always trickled charged and voltages good, yet when i start is it says 12volt low
can a bad cell draw to much from the coil
or a bad regulator cause spark issues at this rpm until it can get up to speed ?

could it be electrical ?
could it be the rave valves oppenning to late ?
have read most of the post available and need some guidance