KZ650 Cylinder head Compatability

I did a valve adjustment on my 1979 KZ650B,and decided to replace the Intakes with new ones I bought about 2-3 months ago.7 bolts came out,1 snapped off about 3-4 mm out.I started drilling with a new bit set,but had to get some stub bits to keep a good angle and make sure I was drilling straight.I should have kept going-I lucked out and the bolt broke pretty flat and about straight across a thread,so it was easy to center a tiny punch and get the hole started.I should have went with a 6.0X1.0 tap or even a heli-coil,but I stopped and tried an easy-out(which is never easy!)My bad-I thought the screw was actually coming out,but I tweaked instead the flange,and this cylinder head is going to the bone yard .Anyway,I am looking for units to replace the cylinder head,and I know that 77-79 B,C and D model heads will work,but what about others?I am looking at a 1980 KZ650 cyl head and the dude doesn't know what model or compatability.Also a 1981 KZ650H CSR one that looks good.Here is one for you experts though...the one I like the most is off a 1981 KZ750 LTD (H model),and the dude swears it will work on a 1982 KZ650H (CSR model).Me -I don't know for sure,but I would like this one.Any help is muchas gracias/greatly appreciated! Our weather here in Ohio has been great for november,and I need to get this bike back up and running!!!I am running the stock carbs.Mikuni VM24SS with accelerator pump.Thanks again!

There are minor differences in the 650 heads, but they should all be usable.

A 750 head can work as long as it has the holes for the top idler and the indentations for the tensioner and front idler on the underside. That said - it will reduce your compression as the 750 has a slightly larger compression chamber in the cylinder head. It also has larger valves than the 650 which may adversely affect your performance without other changes as well.

Any of the heads from (K)Z650 1980 (US market) and before should work without issue. The later ones used a different cam chain hy-vo and do not have the necessary flanges/bolt holes for the older style cam chain top idler.

gd4now wrote: Any of the heads from (K)Z650 1980 (US market) and before should work without issue. The later ones used a different cam chain hy-vo and do not have the necessary flanges/bolt holes for the older style cam chain top idler.

Are you sure about that? It's kind of weird that the 650s have no provision for the roller cam chain while the 750s do.

It is my understanding, and I am not claiming to know all, when the change to the Hy-vo cam chain happened the top idler wheel was removed as well as the bolt holes for it from the head. Instead a plastic or plastic like shim was installed on the cam cover to take up some of the slack in the cam chain between the to cam sprockets.

Again, it is my understanding that some of the eary 750 heads do still have the bolt holes for the original idle wheel but the later 750 and 650 heads do not.

THANX TO ALL that replied to this post.I don't hink I will go with that 750 unit,because even though my '79 KZ650B is bone stock-with the exception of a Dyna S electronic ignition,and some brighter lighting compliments of a Sylvania sealed beam,and upgraded speedo/tacho bulbs-I like how she runs :woohoo: .I think I even like her better than my 80KZ750E right now,but that could change because I know I need ring sets and a cam chain in that bike!I have a friend that is a retired metric mc mechanic,and is also a machinist.He swears that it is fixable,so I am going to bring it to him and find out,but for now I am going to do the replacement thing!Happy Trails! :lol:

gd4now wrote: It is my understanding, and I am not claiming to know all, when the change to the Hy-vo cam chain happened the top idler wheel was removed as well as the bolt holes for it from the head. Instead a plastic or plastic like shim was installed on the cam cover to take up some of the slack in the cam chain between the to cam sprockets.

Again, it is my understanding that some of the eary 750 heads do still have the bolt holes for the original idle wheel but the later 750 and 650 heads do not.

Pretty sure the holes are still there and tapped to take the top roller. That's the way the Kz750's with the Hyvo chain came. As long as he still had the chain roller and other equipment it should work no matter what year.

My 1982 KZ650 CSR uses the hy-vo style cam chain, with the rub pads on front, rear, and top. The holes for mounting the older style roller chain idler pulley are still in my head casting, but no threads are tapped. Probably could be done, but a tedious job, and not one that you would want to have threads strip out or come loose.

From studying heads on ebay, I think that the castings were threaded up through 1980. 1981 and later switched to the hy-vo chain and no center idler, nor threads in the 4 holes in the casting.