KZ650 engine block interchangeable btwn years?

Gotcha,
All that said, what are your thoughts on having a mismatched top and bottom, even if it's from the same model.?

rstnick wrote: Sorry to hear about your mishap.

I've always read that you need to keep, and use the top and bottom halves of the crankcase together, and should not mix top and bottoms from different engines, as the halves are bored for the crank etc with the crankcase together (top & bottom).

This being said, Andy on the 650info forum has recently assembled an engine with mixed top and bottom cases, and so far no issues.

Just rereading this - are you saying that I shouldn't use a crankcase from a different bike than the cylinder head, or are you saying the top and bottom halves of the crankcase shouldn't be from different bikes?

You need a set of cases from a 650 or 750 engine that uses the later HYVO type cam chain which is what should be in your 1980 engine.
You must use a matching set unless you are a very good engineer as the cases are very accurately bored as a set for the main bearing shells and each set of factory bored cases takes a slightly different mix of shell sizes even on the same crank.
There are letters and numbers stamped on the cases and on the crank which when paired together give the colour code for the size shell you need for each individual main.
Later cases have rubber mounts so make sure you get the type that matches yours otherwise you will be having to fabricate new engine plates too.
These eight valve engines featured in many models right up to the 2003 ZR750 with very little change so there should be plenty of suitable donors out there.

His should be a kick start roller chain motor
U.S models didn't get the hyvo chain till 81.

How about posting up some photos of the damage? If possible remove the sprocket cover first.

If it would help I've got a clean set of 1980 750E engine cases (and most of the internal parts too) you can have for the cost of shipping.

If you truly need new engine cases I suspect you would be better off looking for another engine or at least a complete bottom end. There were a LOT of 650/750's built, it shouldn't be too hard finding a decent engine in your area.

Nessism wrote: How about posting up some photos of the damage? If possible remove the sprocket cover first.

If it would help I've got a clean set of 1980 750E engine cases (and most of the internal parts too) you can have for the cost of shipping.

If you truly need new engine cases I suspect you would be better off looking for another engine or at least a complete bottom end. There were a LOT of 650/750's built, it shouldn't be too hard finding a decent engine in your area.

I'll try to take a photo later today, or maybe tomorrow morning. I think my first post was slightly confused - I did mean to replace the damage with a complete bottom end - I was asking about matching top ends and bottom ends, which I now understand is not a problem. Seems like I'll be able to swap out the crankcase and damaged sprockets, and keep my old crankshaft, pistons, and top end. A photograph will clarify a great deal, so I'll get on that. The advice so far is much appreciated.

zukdave wrote: His should be a kick start roller chain motor
U.S models didn't get the hyvo chain till 81.

The US got the Z650D3 with hyvo chain in 1980.
Some other Z650 models still used the roller chain for 1980 while it was being phased out.
1980 also saw the first Z750 - 4 , the E1 model and all 750's were hyvo.

I believe 1980 was a transition year where both types were available in various models. When I was looking for parts for project a few years back 'm sure I saw both types that people said came from a 1980 bike, you had to look closely at the pictures to make sure it was the type you needed.

My F1 was a kick start roller motor

Pics of the damage.

I don't see any damage to the cases, just the covers.
Steve

Looks like a hole in the crankcase just below the clutch pushrod.