Boring kz650 to 700cc, question on overheating

So my local RV shop quoted me for fitting a wiseco piston kit in my 650. He was VERY blunt in telling me I will destroy the bike from overheating and that the sleeve will be too thin and weak.

BS right? Lots of you run bigger pistons with no problems. How many of you have had overheating problems with overbore pistons? I would like to put an oil cooler on the bike anyway, but even if I didn't I still should be OK. Right?

The hotest it gets where I live is about 90 degrees, most mornings I ride to work in August its bearly 70. I mean, if a 750 which as the same cooling ability as a 650 has no problem, then a bored out 650 should be no different. The increase in CR to 10.25 will make more heat, but not that much more... Right?

I don't think your RV dealer knows much about these old Kaws. Sounds to me like he is looking for a way to duck out of backing up his work. If it were me I would ask/look around for someone else to do the job.

Yeah thats total BS. I'm doing the 810 thing in a couple weeks, and I'm not concerned about overheating at all. Sure I'm sticking on an oil cooler, but I'm also putting a thermostat in the line so the oil cooler is bypassed when the oil is too cold, which will be probably 80% of the time. I've been told dozens of times on here that an 810 doesn't need one, so why would a 700?

I put a 716 kit in my 650 in I think 1982 and no problems.
Mark

I don't think so either. The guy at the RV perfomance shop has been doing work for motocross guys and snow cats for decades. I don't think he ever did much on these 4 cylinder kaws.

I talked with afreind of mine who worked as an egineer for Victory. He asked his buddy form the engine design department and he e-mailed me back...

"As a rule the old air cooled Kawasaki's are very durable as they were over designed. Back when I worked in a shop we built a number of the 1000cc Kawasaki's with over bores in the 1050cc range with no over heating problems reported. But the later air cooled Kawasaki GPZ form the 1980's came with oil coolers. An after market oil cooler would not hurt but I can't say it would be needed. Cylinder head temperature increase will depend on how much the compression ratio will increase. It will increase with an over bore but if it stays in the9.0:1 to 9.5:1 I would guess it would be OK with out an oil cooler. I do not know what the cylinder head temperature is on one of these air cooled inline fours but some air cooled V-twins I have worked on have cylinder head temperatures as high as 450 degrees F for short periods of time with out oil coolers. I hope this helps."

I guess I would believe him, he desined the current generation of victory v-twins.

One of mine has GPZ750 factory pistons with no problem. It does take premium gas or it detonates badly though. That's stock GPZ compression, whatever that would be which is for sure less than 10-1.