kz650/750

what is involved in changing the cylinders on a 650/4 to the 750/4 cylinders, will it swap or do you have to do something special

There are many people here more qualified to answer this than I, but as I understand it:

The year of 650 makes a difference. It needs to be one of the later years, as they used the Hyvo cam chain like the 750s.

Guitargeek is right. The later model of the KZ650 (say '81/'82 onwards) with the Hi-Vo cam chain will accept the cylinder block and pistons straight off a KZ750/4. Basically, you use the engine cases, crank, cylinder head and cams off your KZ650 and use the cylinder block and pistons off the KZ750/4

If you have the early model KZ650 with the standard single row cam chain, then you need to enlarge the holes where the cylinders slide into the engine cases by around 1mm (from memory). This is not a big job and can be done carefully by hand but it is better to have it done proffesionally.

You can swap the KZ750 cams into the older KZ650 head by swapping the cam chain pulleys. This is desireable as the later model KZ750/4 cams had more lift and duration than the earlier KZ650 cams, if I remember correctly. Later model KZ650 cams where the same as late model KZ750/4 cams.

Post edited by: Murphyau, at: 2005/12/02 03:33

Yeah, what Murphy said...

Two questions on the 750 cam swap into the 650 head. What about the tach gear drive and what kind of powerband/horsepower benefits can one expect from this swap. I know the 750 head also has bigger valves but don't want to get into changing cam chains as mine only has 14000 miles on it. I have a '77 KZ650 and another local Kz fan has a top end from an 82 KZ750 he is willing to part with...for nothing. I figure the price is right so why not?

Cheers-Colin Firth
'77KZ650 brought back from the dead, totally rebuilt and massaged in all of the right places.

The 750 cams have the area cast into them for the tac drive it's just not machined for the gear drive. You should be able to have the cam machined fir the drive.

On the 650 750 swap it has to be a later 650 with the hi-vo cam chain. The 750 hi-vo cam chain tensioner won't work with the early 650 single row cam chain.
Mark

I have a KZ700 this will work also, are the 700 parts the same as the 750, is a 700 a good engine,I have two early 650s both 78s and am looking at an 80 750 parts engine

If you are looking at the whole 80 750 engine you might as well just put the whole thing in. It should fit right in. The 650 to 750 I did went easily.

the lower half of the 750 is broke,but I have an 84 KZ700 engine that runs great,just don't know how it would compare to a 650 as far as performance. there is nothing wrong with my 650 engine other than mileage, so I thought I may put the 700 on the bike and build the 650 for another bike I have with no engine

i'm not hijacking the thread, but if anyone wants to try this swap, i have a complete 750 motor in my barn that would like a home in a kz.... its an 82. shoot me an email at brianbeck@cox.net