The water pump on that engine was actually replaced, not rebuilt. It came off of a new Super 9 engine that was the result of some recall back in the day. Something to do with the structural integrity of the CVT side crankcase... the recall was before I was really privy to Kymco. That said, the water pump should hopefully be okay, but hotter running can certainly have an affect on things.
The high compression ratio is a factor, yes, but in my opinion (I have not verified with tests) the Prima cylinder's waterjacket is a more contributing factor to the heat than the cylinder head. I went out to the shop just now, and snapped a few quick photos in effort to illustrate the point:
Above, is a stock liquid cooled cylinder. Note the water jacket.
A Prima (or Char-Mo) cylinder, seems to be very close to what I would expect to see from a stock cylinder that has been re-bored. I didn't have an extra Prima laying around, but I marked the cylinder with a scribe line to show the approximate re-bore. The water jacket is the same, therefore you've got more surface area in the bore, a bigger piston, more air, (likely) higher temps, and with the same amount of water moving around the parts to cool 'em down.
This photo shows the Stock Super 9 cylinder next to a Malossi cast-iron, and an Airsal. Notice how both have significantly larger waterjackets.
The engine in bertha was originally built an a stretched budget - thus the Prima cylinder in the first place. For what it is, I felt it was doing alright, but I don't like to know that it's running that hot! I've got to get on the ball and send you that other cylinder head. Despite the fact that the water jacket on the cylinders are different, the cylinder heads themselves have quite a few differences.
Cheers!
~Josh
