1979 KZ650 big bore

I have a 1979 KZ650B that when I bought it the guy told me it has a 720cc big bore kit on it with a 750cc head. Is that possible? Does the 750 head fit the 650 block and cylinders?

Yes, common mod.

do you know would I order a 650 or 750 header or are they the same?

The headers will be almost the same, although there are some variations in how they mount to the bike at the rear.

Welcome.
Post up some pictures when you can.

650/750 exhaust header spacing is the same, as are many 650/750 parts being swappable.
The 750 (738cc) engines are based on the 650 engine.

Some pics to show interchangeability of exhaust systems.
Here's Andy-the-Gringos 650 w ZR-7 exhaust. I think the ZR-7S is the same. (1999-2005 ZR750)




1981 KZ650-CSR w 1980 KZ750-E1 mufflers. direct fit. the 750E mufflers are 6" longer than the csr's.
both have a center stand recess in the left side muffler. the 70s mufflers don't have the recess.

This exhaust system may still be available.

www.kzrider.com/forum/23-for-sale/606327...em-chrome-vgc#765796

No eBay APP ID and/or Cert ID defined in Kunena configurationYoshimura kit, very rare now:

Hey Tyrell Wiseco made a 720 and 740 kit for years and finally dropped em for only the 700cc kit.....

if he has them would they be different ?

Don't know much about the 720 kit, other than I have a 12:1 cast piston race kit 3 ring 590 gpz550 kit.

They made different kits, from two ring and three ring in varying CR.

OP if these are anything like mine the ring wire circlip is 0.8mm...unobtainum for the 590 gpz kit , I had to make some teflon buttons. They actually went to all the effort for reducing reciprocating weight by a few milligrams.

Finally, the bore clearances are different on these. I have some tech info from Yoshimura Japan but was requested not to openly publish it online, pm me if you need.