83 kz750 cylinder head to 78 kz650?

Will '83 kz750 cylinders/pistons fit on my '78 kz650?

alberto.f.a wrote:

Will '83 kz750 cylinders/pistons fit on my '78 kz650?

Yes the cylinder block and pistons will fit on the 78 KZ650 if you clean up the bores in teh case so the liners will fit.

As far as the cylinder head, I know 80-81 KZ750E and KZ750H heads will fit, I think the same heads from 82 will fit, 83 I don't know, except that 83-85 GPz750 heads require some work to fit.

So I assume you are not aware of member Dave Sloan with his 810 kitted fuel injected KZ650?

Very cool bike

Or member Reborn650's 810 kitted carburetted KZ650?

Another nice bike

Easier (if you have the whole motor) is just installing the 750 motor as a whole.

Cool, thanks for the quick reply. Well, my bike has 52,xxx on it right now, and from reading other posts I figure my engine getting/is tired [I dunno, my first bike and doesn't have the power to wheelie(i don't condone or practice)like others mention about a stock 650] , and since a rebore would be more expensive than just slapping a different head on there (at this point just getting new rings is more expensive than getting a used head/pistons)
I figure i could just get the cylinder/pistons now and keep them aside until i get an excuse to swap.

Oh another question, vm24s + rejet = big enough for the swap?

Head has nothing to do with rings/pistons/bore, it's the top part that holds the valves and the carbs/exhaust attaches to it.

As far as buying a used cylinder block and pistons and bolting them on your lower end, and having the engine have good compression and not smoke afterwards, if you're that lucky you should spend your money on Lottery tickets.

KZ650's don't pull the front wheel up using strictly power, there's only 64 hp there at best when new.

750 cylinder block with Wiseco 810 kit is the ticket

I wouldn't judge the condition of the engine based on whether or not the bike will easily wheelie. Steell is right, KZ650's didn't pull wheelies easily even when new (I know because I bought mine new in '77). A better non-technical test is whether or not the bike will idle smoothly at 1,000 RPM and quickly and smoothly accelerate up to redline (9,000 RPM) in every gear - topping out at roughly 120MPH (indicated). Mine would do that when new and still will with approx 48,000 miles. This test may not provide the most scientific or accurate measure of engine condition, but it sure is fun! (Check local ordinances before running test;) ) Ed

Oh, I'm sorry i didn't mean the head, i meant cylinder block/pistons. i do that sort of thing all the time.

Yeah, i wouldn't know about the power i can expect out of my bike since it's my first, but i at least i can positively state that it runs a hell of a lot better than when i first got it. yeah it idles smoothly and accelerates smooth until 9k (although a bit buzzy, but i think that is expected)

well you guys talked me out of it, i guess ill just spend my money on making it look less like a rat. and then saving my pennies for a wiseco kit down the line.

thanks for the info!

just about to do the same on mine but its a 81 750 head barrles pistons going on a 77 650.
bit of port work and some 32mmcv carbs coming my way as well i hope. if not i'll be fitting the stockers back on and playing with jets.

Ok,well Ive got another question concerning the same thing basiclly yet not. Will the crankshaft & all up from an 81 kz750 work in my 84 zn700a1 cases.

Nobody has mentioned the issue with the timing chain and tensioners. The 77 kz650 has a peanut chain but the 80's vintage kz750 has the hyvo chain. The chain and tensioner systems are different. The 750 has a slipper on the top of the valve cover while the 650 has a sprocket bolted to the head. The 750 uses chain guides while the 650 has rollers and sprockets. So when you put the cylinder and head from the 750 onto the 650 block you need to account for those issues. I have an 810cc wiseco kit in my 650. My solution was I cheated and had LA sleeve make me cylinder sleeves that I installed into my 650 block then bored them to the required size. I used the 650 head which I ported and used the GPZ750 cams with the 650 sprockets. That way I was able to use the existing timing chain and tensioner setup.
I guess you could use the tensioner setup from the 750 but I don't know if that would work with the peanut style chain. I didn't want to risk trying it that way as I had a lot of money in it and didn't want to risk it.

In January 2009 Judgie wrote: "just about to do the same on mine but its a 81 750 head barrles pistons going on a 77 650. bit of port work and some 32mmcv carbs coming my way as well i hope. if not i'll be fitting the stockers back on and playing with jets. "

Yeah, right. Why didn't Judgie mention the differences between the 1977 KZ650 and the 1981 KZ750 cam chains and their associated sprockets/rollers? They are really very different and I seriously doubt that Judgie was ever able to make the combination he mentioned work unless he solved that compatibility problem. I notice that the last time he logged onto KZRider was in 2010 - ten years ago! Ed

By Frankenbike1: Ok, well Ive got another question concerning the same thing basiclly yet not. Will the crankshaft & all up from an 81 kz750 work in my 84 zn700a1 cases.

I don't know & could be wrong, but I bet yes. From the diagrams at Partzilla the ZN700 has the same crankshaft as the 83 650 & 750-L3 models. The 650-CSR engine is basically the same as the 750-4s. Instead of replacing the crankshaft, I would look into getting an engine from a 750 Shaft, either an 82-83 Spectre or 83 750-F1 Ltd Shaft >> probably direct swap, but don't quote me on that. Or get a correct crankshaft.

In regards to the 70s 650 question, I've never done it, but some 750-4 cylinder heads have provisions for attaching the upper cam chain roller assy & from the EB pics I've seen I think the bolt holes are threaded. some don't have the bolt holes drilled, though. The shape of the cam chain tunnel looks the same. But I have no idea how much work it is. I would do the easy thing & just swap engines. :blush: