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In March 2020 I upgraded my 1100 stock clutch with a set of Barnett 501-40-06058 heavy duty clutch springs.
The clutch traction definitely improved with hardly any noticeable change in clutch lever tension.

But the left hand has been feel'n the difference this year.  YOWZA!

Some folks alternate stock and aftermarket springs around the pressure plate to get some extra pressure on the plates and less owie in the left hand than a full set of stronger springs make.

wrote:

Some folks alternate stock and aftermarket springs around the pressure plate to get some extra pressure on the plates and less owie in the left hand than a full set of stronger springs make.

Now then, why didn't I think of that?  I will add that to my Spring schedule right now, while I'm thinking about it...



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Take a look at page 5 of the attached thread, surface grinding the steel plates will increase the friction without the need for heavier springs
1981 GPz1100 B1 Rstomod / ELR "Tribute" - Page 5 - KZRider Forum - KZRider, KZ, Z1 & Z Motorcycle Enthusiast's Forum

I remember a old package of the street springs I bought said 10% stronger. I have those in my bike and zero issues.
10% is about 5psi on every spring x 5 = ~ 25PSI pressure increase at the clutch hat... That's not a lot.

To estimate the difference between stock and "HD" - look at the length and diameter difference with a vernier. That will let you know if they are crazy different, if they are hard to pull in they will never in your lifetime "soften".

Barnett did sell different colored springs that were stronger, the wire thickness was more, I think green/yellow/red. The red ones I had as they were for drag racing, but don't have them any longer so don't know how much more pressure they exerted. They were quite hard to pull in until you got use to it so I figure those may have been 30%??

There is no difference in the springs on KZ650/750/900/1000/1100 all fit the same. There may be a slight difference in the installed height which may make a few PSI difference but you would never feel it.

Stock KZ springs make 46lbs @ .990" installed height (about .11" compressed from stock)

I have a lockup clutch in my drag bike so I have a spring checker and a list of various springs. Of course the springs wear then pressure decreases, you can shim them but if you don't know what your doing you can damage your fiber plates.
 

Install a hydraulic clutch and you will never ride without one. On a Zed or KZ it just takes a small amount of material removal from the back of the housing and a Yamaha slave can be mounted. Shorten the push-rod a minor amount and you're good.

Give it a try and add some extra pre load pressure. Shim some washer under your clutch springs for no money.