kz650 and kz750 bottom end the same?

I was wandering if the bottom end on these engines were the same? Can I take a top end from a KZ750,only 4cyl, and put on the bottom end of KZ650?

I know the KZ650 has the kickstarter and this is the main reason I would want to do this. Will it work? I know there may be some other ways to do this but this would be the easiest to me.

Thanks
Ray

rayellis wrote:

I was wandering if the bottom end on these engines were the same?

Well, physically they're the same on the outside, a 750 engine will bolt straight into a 650 frame.

Can I take a top end from a KZ750,only 4cyl, and put on the bottom end of KZ650?

The short answer: No, not just like that.

The long answer: Well, yes and no. You can put a 750 block and head on a 650 bottom end, but in order to make the 750 block fit you would have to machine/grind the upper case at the cylinder base as the 750 sleeves are too large to fit in the 650 case - in my world that would require splitting the cases prior to machining as you don't want metal shavings in your lower end.

Next issue is the cam chain, depending on what year 650 we're talking about. The early 650s (B1/C1 - F1) have a single roller cam chain and cam chain idler gears, whereas the 750s and late model 650s (F2 and up) have a hy-vo (multiplate) cam chain and cam chain sliding blocks (including one in the valve cover).

What is really the issue (unless you have an F2 > 650, which as far as I know would still require machining the upper case to accomodate the 750 block) is that most 750 blocks, except for 80 and possibly a few 81 models, do not have the provisions for the cam chain idler gear shafts nor do they have the provisions for the top idler gear tower so you can't use them with a single roller cam chain. Also using a 750 head and cams with a single roller cam chain you'd have to transplant the 650 cam sprockets to the 750 cams although that's a minor thing.

Then again, if you're going to split the cases anyway for machining the upper case, you can swap a 750 crank into the 650 cases, maintain the kickstart and use the 750 top end in which case you'd use the 750 cam chain, cam sprockets and sliding blocks including the 750 valve cover.

So basically, it can be done, but it's not a bolt-on, button up and ride thing.

That tells me a lot more to it than I thought.I thought the 650 was the same engine except the top end. Shows what I know; not much.

Thanks OnkelB you folks at kzrider are the best. I don't know if I want a kickstarter that bad.

Kickstarts do have their moments . I've had battery connection issues that wouldn't let me crank, but I could and did kick it to life to go home.

That said I'm probably going to just swap the whole motor.