Question on KZ650 Cyclinders

Sir's

I'm trying to find out what the out side diameter of the KZ650 cylinder sleeves are.   I read somewhere that there might be a difference between the earlier years and later years..if so what?

I'm trying kz650.info but haven't found anything yet.  

Why?  Crazy haired brained idea that might not work but might so I'm just doing the math.  

Thank
577nitro.

It seems like all the cylinders from the beginning of the 650 run through 1980 use the same cylinder PN.  After that, the cylinder changed, in part because Kawasaki changed to a link plate cam chain.  

If your idea involves bigger pistons, realize that a 750 cylinder will also fit the 650.  You just need to find a cylinder with the proper cam chain opening.  There is lots of info on this topic on 650.info.  

I know the answer but I want to hear the why first.

wrote:

I know the answer but I want to hear the why first.

wrote:

I know the answer but I want to hear the why first.
 

Ok...I have a set of old GPZ550 cylinders and per my exhaustive research and measuring I think I can remove the liners from the block, mill the block open enough to get the 650 liners to fit.  It will take some tweaking here and there but there is enough room barely.  Yes some things like the lip will need to be mill back and some other things, but it will fit. 

I know the length is too long etc...but I can cut all that down on my lathe.  If this fits as I think, the bore will be 64mm, stroke will of course remain the same.  IF, I can keep the cylinder wall thickness the same (IE: Not having to back cut the cylinder, then the bore could even be taken to 66 mm, per the Weisco Big Bore Kit I found.  The other problem is that the wrist pins on the 650 are 15mm and the 550 is 14 mm.  It might be possible to hone the small end .5mm per side get it to 15mm and use the 650 pistons.  For ~200.00 per piston, I could get a set of custom 14mm wrist pin pistons made to order as well. 

The "Why" do it when you can get a 615 BB Kit?  There is no replacement for displacement, and its fun to do things people say can't be done.  A 700cc GPZ550, what fun that would be.
Why not just put a 750/650 in the 550?  Heavier, harder to do, another engine to rebuild.....etc.   

My Calculations at 64mm bore that's 674cc at 66mm 717cc.  If I had to back cut the cylinders, I would loose probably 1mm so I could max out at 695cc.   It could all fail spectacularly as well, never know till you try.  

Power?  No idea, but I'm guessing maybe 5 to 10hp out of the box.   Ported, cammed, bigger carbs, higher compression, maybe get 75hp at the wheel.  I'm just guessing.   But I really think the torque is the big plus.

I thought I saw somewhere on the interweb were some Japanese guy had tried something similar.

577nitro.



 

wrote:

I know the answer but I want to hear the why first.
 

And....????????

The 550 bottom end isn't exactly overbuilt.  I'm not sure, but doesn't the engine share parts with the 400 version bikes as well?  Seems like bumping that bottom end all the way up to 700+cc is asking for trouble.

The transmission will be fine.

The 550's have a history of wiping out crank/rod bearings.

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The 550's have a history of wiping out crank/rod bearings.

 

Really, never heard about that before.  I have heard that when raced the 750’s would spin the mains under hard braking due to the oil pickup un-porting.  How do they fail?


Thanks
577nitro

wrote:

wrote:

The 550's have a history of wiping out crank/rod bearings.



 

Really, never heard about that before.  I have heard that when raced the 750’s would spin the mains under hard braking due to the oil pickup un-porting.  How do they fail?


Thanks
577nitro

 

Where did you get that info?

Have you ever looked at a 650/750 oil pan?? It has a cast in "wall" that is similar to the 900/1000 but a bit tighter to keep oil on the crank plus the 750 oiling system was improved over the 650 which is a high pressure system to start with.
 

wrote:

wrote:

I know the answer but I want to hear the why first.






 

And....????????





 

I don't know where your getting your information from but its incorrect.

The max a 650 liner can go too is 65mm (720cc) and then it is very thin as in "race" (.070" per side) The 750 (738cc) piston is 66mm stock.

The 650 liner is 68.5mm OD!!!!!!!!!!!!!

Your idea of increasing the wrist pin diameter is very dangerous to your project. Those type of modifications are generally used on race engines that don't see any miles, but feel free to modify away.

If you did the math you would find out the piston speed for that bore/stoke combination, along with that dodgy con rod mod is bound to have a catastrophic failure. That is why it is best to stick with proven overbore combinations that are sitting on the shelf.

There are many GPZ550 guys on here, been on here for donkeys ages. If it would be possible to go bigger it would have been accomplished already.... maybe 15 years ago.