Clutch issues

[Andy Lee]

Apologies if this has been covered before, but I am new to the site. I hope this is the right place to post as well.

I have a 1974 Z900 A4. On cold start the clutch works fine, but once the engine is hot, it loses any graduation and is like an on/off switch which makes controlling the bike quite difficult. My initial thought was to replace the plates and springs, but if it is any deeper than that, I'll have to get professional help. The cable has been removed, cleaned and re-greased and the lever adjusted etc.

Any suggestions will be most welcome. Many thanks.

[warren3200gt]

What oil is in it? Needs to be compatible with motorcycle wet clutch.
Having said that I would expect the opposite if it was a oil issue, slipping when hot, but you never know?
I use good ol mineral 20/50 in all mine and just change it at least once a year. None of this semi or fully for me. It wasn't available when they were new so they weren't designed for it.

[chrisu]

check the release worm drive. I had a lot of problems with the one on my Z1. Swapped for an Eazyclutch from PMC and its really smooth and light now.

Maybe the clutch basket has notches - also worth checking.

[steve452]

1974 A4? They're rare.

[Andy Lee]

Sorry steve452, you are quite right to flag - it's a 1976 A4.

Thanks for the suggestions everyone. It has only had mineral oil for many years according to the previous owners.

I think it may be a case of trial and error....

[wilsonsjw11]

The release worm drive may need some light grease, classic symptoms are that the clutch lever gets stiffer as the engine warms up.
Regards
Steve