KZ650 vs KZ750 clutch

Does anyone know how big a difference there is between these two clutches? The reason for asking is that my clutch on my KZ650 engine seems like it needs replacement. The caveat is that the KZ650 engine is fitted with cylinder, pistons and heads from a KZ750, so I am unsure about whether I should go for the friction plates from the KZ750 instead? As far as I can see the springs are exactly the same part number for both, but the friction plates seems to have different numbers. So, does anyone know if the ones for the 750 are "better" and will they fit my KZ650 "housing"?

According to partzilla both the 650 and 750 share the same clutch plate part numbers. Where are you seeing that they are different?

Nessism wrote: According to partzilla both the 650 and 750 share the same clutch plate part numbers. Where are you seeing that they are different?

On cmsnl.com the springs are the same, but the friction plates have different part-numbers. But if they are the same on partzilla, then there cannot be too much difference between them.

q-base wrote: .............The reason for asking is that my clutch on my KZ650 engine seems like it needs replacement............

What motor oil are you using? If it is not JASO-MA compliant it may very well be the reason your clutch is slipping. Ed

By q-base: On cmsnl.com the springs are the same, but the friction plates have different part-numbers. But if they are the same on partzilla, then there cannot be too much difference between them.

What models were you comparing? I'm seeing the same part numbers at Cmsnl.com for the 650-F1 & 750-H1. and several other models are the same as well. maybe you chose a 750-Twin?

650ed wrote:

q-base wrote: .............The reason for asking is that my clutch on my KZ650 engine seems like it needs replacement............

What motor oil are you using? If it is not JASO-MA compliant it may very well be the reason your clutch is slipping. Ed

I actually just changed the oil for one that is advertised as motorcycle oil. But I got the same idea and looked it up - it is not JASO-MA compliant. But to change the springs and plates I have to drain the oil anyway. So my thinking is that if I have to drain the oil anyway, then I might as well change the springs and plates. I cannot be that difficult and I do not know the history of them. If I only try to change the oil then I might end up having to change it twice if it does not solve my problem. That is my reasoning at least:)

martin_csr wrote: By q-base: On cmsnl.com the springs are the same, but the friction plates have different part-numbers. But if they are the same on partzilla, then there cannot be too much difference between them.

What models were you comparing? I'm seeing the same part numbers at Cmsnl.com for the 650-F1 & 750-H1. and several other models are the same as well. maybe you chose a 750-Twin?

I actually had the exact same idea walking home from the gym just now - that perhaps I had compared the twin with my 650.

All things point to them being equal, so I will just buy for the 650 and rely on them being strong enough for the few extra ponies.

Thanks a lot for the help!

q-base wrote:

650ed wrote:

q-base wrote: .............The reason for asking is that my clutch on my KZ650 engine seems like it needs replacement............

What motor oil are you using? If it is not JASO-MA compliant it may very well be the reason your clutch is slipping. Ed

I actually just changed the oil for one that is advertised as motorcycle oil. But I got the same idea and looked it up - it is not JASO-MA compliant. But to change the springs and plates I have to drain the oil anyway. So my thinking is that if I have to drain the oil anyway, then I might as well change the springs and plates. I cannot be that difficult and I do not know the history of them. If I only try to change the oil then I might end up having to change it twice if it does not solve my problem. That is my reasoning at least:)

I agree. A number of years ago I had to replace the clutch in my KZ650 because the oil I was using wasn't JASO-MA compliant and ruined the clutch plates. Ed

its the same clutch

Have you adjusted the clutch per the factory manual specs? I'd do that and lube the clutch cable before looking at changing parts.

Oils get way too much blame when clutches start slipping. Most of the time when parts need replacing it's just the springs anyway.

BTW, what kind of oil did you use? A motorcycle oil that damages clutch plates would be extremely unusual. Only oils with friction modifiers do that.

Nessism wrote: ...........BTW, what kind of oil did you use? A motorcycle oil that damages clutch plates would be extremely unusual. Only oils with friction modifiers do that.

Excellent question! Ed

650ed wrote:

Nessism wrote: ...........BTW, what kind of oil did you use? A motorcycle oil that damages clutch plates would be extremely unusual. Only oils with friction modifiers do that.

Excellent question! Ed

To expand on this, there are plenty of oils that are not JASO-MA but will work just fine. Just because an oil has not been tested for compliance doesn't mean it won't work. There are many people who swear by Shell Rotella in motorcycles, and that's a heavy duty diesel oil.I've never tried it personally, it's not JASO-MA, but it is very well tested.

Best to go for a JASO-MA oil to be certain. My first KZ - a KZ250 - had a slipping clutch that would also drag when cold. The oil was definitively wrong when I got it. Changing to a motorcycle oil fixed the drag, but could still get clutch slip.

I eventually replaced the plates and springs (I bought a full kit), however both the springs and plates were still within service spec. I'm pretty confident it was the incorrect oil sitting in the engine for such a long time that had the clutch slipping. New plates and springs, and I could wheelie that little 250 by releasing the clutch too quick.