Compression would increase, but you'll have the wrong squish band clearance.

 

Because the bore is 7mm smaller? Can this be modified?

 

yes you could re cut the head. what is wrong with your 600 head?? 600 heads are a dime a dozen used and can be had for cheap.

 

Face it. Cat and Suzuki know a lot more about engine design than you or I. You could make a 500 head run with a little work, but I bet it won't run better than stock.

 

I have a 500 head and I'm putting pistons in my ZR600 and I ride it at 8000 to 11000ft. and I want to make up for the compression I'm loosing at this altitude.
I was thinking that this might be an easy/cheap way to boost the compression.

 

Boosting compression doesn't do as much as one thinks. I forgot the ratio but it's less than you think

 

The few hp isn't worth the Gas requirement or power you would get to have that head re cut. I would find a set of used twin pipes and Jet or carb mod it. You would get better results with that.

 

Well never mind, I took the head off of the 500 to see what's different and it's been cut out to 83mm so it's not a 500 it's a 680 and actually the pistons read 83.80mm with a A48K2 # also stamped on them. Anyone have any info on these pistons???

 

Wiseco makes a 680 big bore piston kit for the 500/600. You probably have iron sleeves instead of nicasil coated cylinders.

 

I thought that too but wiseco lists the kit for an A case only and it's 83.0mm these pistons read 83.90 on them in a B case.

 

8380 or 8390. Does it say mm after the numbers? Could be part of the part number. The A case per your other post has the 20mm wrist pins, the B case, 22mm. They may have made the kit for the B case motor at one time.

 

I'm sorry, it's 83.90mm. I mis read it the first time and it also has this # A48K2, I'll take pics.

 

Here are the pictures. I also noticed that the 500 cyl. was made in the U.S.A. !