TOPIC:

Hi, I had this on the old site, but I still have a few questions. My bike is a 77KZ650B. I recently burned a piston after installing a MAC 4-1 pipe and pods (hadn't rejetted yet, was waaay too lean). So I was going to buy all new pistons and was thinking of the 700cc kit from wiseco, until I heard that the kz750 jugs would fit with a little case modification, and wiseco had an 810cc kit for the kz750 jugs. Bigger is better right? A few guys on here had heard of this being done before, one guy even had done it himself. He used the kz650 head on the kz750/810cc jugs with 29mm smoothbores. Now, will the head gasket from the 810cc kit work with this type of setup (kz650 head), or will I need a custom one? Also, what type of carbs are on my bike?, also the kz750? I think mine are 24 or 26..., and If the carbs from the 750 aren't 29mm, would they still be big enough if jetted correctly, or since I'm buying a different set (I just have my stock kz650 carbs), should I just look for the 29mm's? Also, any baseline jetting specs would be greatly appreciated. thx

The 810cc head gasket will probably work. I previously posted that you'd need a custom head gasket, but now I'm pretty sure I'm wrong.

I'd run stock carbs and the air box if you still have it to start with. You are going to see a huge performance boost with all this stuff anyway, and pods will make re-jetting more difficult. 29mm smoothbore carbs are probably an easy longer term fix. You could go bigger but there are lots of knowledge and parts for the old Mikuni 29mm carbs around and they work well with pod filters.

Steve darlington on the KZ\GPZ750 mailing list at www.gpz.us has experience putting a 650 head on a 750 block. He should be able to give you a better idea of how that works. He also is a great source for parts and knowledge on these bikes. He's been vintage racing a kz650/750 for years.

Last, look for some cams to go in that motor. I'd love to see what an 810kit would do for my bike. I thought about this but decided to go the easy route and just did the 700cc kit. With the 700cc kit the cams made a huge difference. Much more RPM available and the power peak moved up to 10.5K.

If you want to get really wild, ARIAS has supposedly made a set of custom 880cc jugs and pistons for a drag bike. That would be expensive but way cool. I'd guess your looking at a few thousand to get this done. And I think you have to re-sleeve the block which will include more machining costs.

You might also want to start looking around for an oil cooler. With 80HP I've never seen an issue with overheating. I live in GA so that includes 100+ degree ambient temps. But I also run a rich mixture and only get about 28mpg. If you live in a hot climate an oil cooler would be a good thing with this type of motor.

Look at the two GPz750 FAQs listed in the links section and I think you will find some good info

Post edited by: steell, at: 2005/10/13 19:04