TOPIC:

My KZ650H runs great but tops out at 55 mph and 4000 rpm.  That seems like the rpms are WAY to high and it needs to be geared down. Am I wrong?

When you say it “tops out” what do you mean? Are you saying it won’t go anymore in any gear?

4000 rpm at 55 mph sounds about right.  The engine is built to REV, so rev it and enjoy!

Doesn't 55mph seem a little slow? It won't rev higher than that.

If it won't rev past 4000 then that is a totally different issue

NOW IS THE TIME ON SPROCKETS WHEN WE DANCE!!

Wookie58 wrote:

If it won't rev past 4000 then that is a totally different issue
 

Could the ignition advancer be hanging up (i.e. not advancing)?

ellwinger wrote:

My KZ650H runs great but tops out at 55 mph and 4000 rpm.  That seems like the rpms are WAY to high and it needs to be geared down. Am I wrong?
 

A good running 650 four cylinder should "top out" at 110MPH @ 9000 RPM.

Assuming you have an 85mph speedometer, a 650-CSR should be able to peg the needle no problem with power to spare.

Make sure the battery is good and fully charged. I would do a load test. 

Ignition coils. ride the motorcycle at speed, then stop & feel them. don't get burned by the valve cover.
The ignition coils should get warm, not hot.  Mine were very hot to the touch, so I got new Dyna coils. 

Clean, check & lubricate the timing advancer. make sure the springs & stuff are good and not rusted or damaged or anything. 
Separate the rotor from the body while servicing & fill the groove w grease. Afterwards, operate the advancer by hand >> the rotor should snap back when released. This stuff is in the manual.  

Has all of the routine maintenance listed in the owner’s manual and the factory service manual been performed  recently? If you are not 100% sure about any item on the list, I would start at the top and do each and every item as listed. In the process, you are quite likely to find the problem, and when you finish the list, you can be sure the bike is performing as designed. Following the schedule will insure that you have a well-running, reliable ride.

Advancer works great. seems like it gets no gas above 55.

Everything checks out. Doesn't seem to be getting enough gas above55.