Topend swap 650 to750 possibe?

Hello everyone,I just purchased a 1977 kz 650 for $300.I want to do a 900 or 1000 but the right one hasnt come along yet.So I seen this and the price was right. The bike is in good shape (no tears in the origanal seat, the wheels and spokes look great,and the chrome also.I am going to tear it down and go through it all.I got access to a 1980 kz750 with a busted case and was wondering if I could interchange the 750 topend onto the 650 lower end.Thanks Dave

it can be done.
why not just do the 810 kit instead?
see reborn650's bike and listen to what he has done.
he has done a beautiful job with his and it sounds like a nasty bitch.
if you have access to a 750, it is the only thing that makes sence to me.
i would be afraid to run his 810 against my 1100.
he seems to have his dialed in perfect.
(plus he is a hell of a nice guy who offers advice on how to make a damm near clone of his)

kawsakiman wrote:

it can be done.
why not just do the 810 kit instead?
see reborn650's bike and listen to what he has done.
he has done a beautiful job with his and it sounds like a nasty bitch.
if you have access to a 750, it is the only thing that makes sence to me.
i would be afraid to run his 810 against my 1100.
he seems to have his dialed in perfect.
(plus he is a hell of a nice guy who offers advice on how to make a damm near clone of his)

How much is a 810 kit and who sells it?The wristpins are they the same between the 650 and 750? Is it a easy swap or what type of mods do i have to do? Easy swap(off one bike and on to another?

I also think I will be able to use the 2nd front disc and caliper for my 650.Thanks for the info..

Thanks for the kind words Steve. Where ya been lately?

As Steve mentioned, I am pleased with the power I have squeezed outta this little 650/810 platform. The Gpz cams and WG smoothbore carbs have really woken this combination up. Add these to all of the other upgrades I feel that I have achieved my goal of a nice little middleweight sleeper that will run with the big boys.

Last week I handed over the keys to a die-hard Kz guy that has owned a dozen or so 900/1000's. He took it for a scoot and when he came back said he was surprised how strong the bike pulled all the way up to redline. He told me that with the lightweight frame, the 810 motor and the grearing my bike would outrun his stock big K bikes up to 75 mph.

BTW, I am still toying with the idea of stuffing a tweaked 1000 motor into a 650 frame one day since I have an extra set of professionally painted bodywork that is looking for a home. Maybe Steve and I could build one from our extra parts bin.

Cheers-Colin Firth-Ontario Canada

I got into these bikes when i was a kid my dad had a brown kz 900 then got a 1978 z-1r I believe thats the right year.I have got into restoring older bikes as a hobby.I have done a 1977 Yamaha xs650,2-1974 Honda ct-90,I am working on a 1976 Honda goldwing LTD right now.I am turning a 1978 xs650 into a street traker this winter also.Then i can put full steam forward on my bike.

Hey reborn thats a pretty disturbing avatar.Do you have any pics of your bike?

Ifixjunk wrote:

Hey reborn thats a pretty disturbing avatar.Do you have any pics of your bike?

The avatar is ridin' a naked hog...or is that naked on a hog? Either way it ain't me:)

Here is a pic of my 1977Kz650 in my shop. It took a lot of time and cash to get it to this stage as the bike was a basketcase when I brought it back to life.

Good luck with your project. If you have any questions on the 810 upgrade there are a bunch of us that might be able to help you out.

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2007/08/03 00:53

For the 810 kit you will have to bore your cases.
You will have to bore them anyway for the 750
cylinder.With the 750 cylinder you can go 810 with
the stock sleeves.The 750 head has bigger ports and valves than the 650.I think the cams are a little
better also in the 750.

Sharp bike reborn.Other than boring the cases is that the only so called problem?

Ifixjunk wrote:

Sharp bike reborn.Other than boring the cases is that the only so called problem?

Thanks.

Cases must be split and opened up to accept the bigger bore of the 750's sleeves. The motor should be out of the bike to make things easier. This isn't a big job but it helps to have a buddy take some of the weight.

I have a couple of posts on how I did the cases using an aluminum cutting bit on my variable speed hand drill. Take your time and gradually remove the 650's cases material and do frequent test fittings.

The early 650's had a roller cam chain and the later 650's and 750's (except the 1980 Kz/750/4) have a hy-vo chain. If you are mixing and matching parts from engines that have the two variations of cam chains you will have to swap the cam sprockets.

There is a ton of info on the 810 upgrades in the archives. When you get to the parts collection stage we can lend some advice.

You won't be disappointed with the 810 should you decide to go that route/

Cheers-Colin Firth-Ontario Canada

Ifixjunk wrote:

I also think I will be able to use the 2nd front disc and caliper for my 650.Thanks for the info..

Take a closer look, the 80 KZ750 disc has a different mount than the 77 KZ650.

The caliper should bolt on, but using both 750 calipers would be a better idea.

I used 83 GPz750 calipers on my 79 750 twin, had to get new brake hoses though.

Post edited by: steell, at: 2007/08/04 07:33