Mine was cutting out @ 50mph @ 5700rpm.
After my clutch work from airdam.
I was climing up 6400 rpm b4 the work.
Then I was on a down hill and that confirmed my 50mph speedlimiter. The rpm's were way down but still would cut the engine out at 50mph.
The dynatek cdi got rid of the limiter. The only hold back now is engine power to get top speeds. Seems not to want to pull much faster than 55mph.
But I have a 4seater, 27" xtr's, windshield and real heavy.
i made the change you can swap the cdi,the one for the 650 h1 quad is the same,you will only gain 300 more rpms.i found out the hard way bought one through speedwerx,and its the same one they use on the quad,369 dollars tossed out the window. get a dynatek 8000 rpm advance timing,no reverse limiter.you will blow the motor first.
got my new dynotek cdi installed,made a difference 8000 rpm limiter did away with the reverse limiter and it advances the timing 4 degrees.when I put it in, it raised my Idle 200 rpms.also got a dyno spec sheet with it.it is a digital cdi box for a carb motor.