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feetupfun

Kawasaki KT250 clutch question

8 posts in this topic

Has anyone tried riding trials on a KT250 using only three of the six clutch springs?

I've done this with a couple of TY250 twinshocks and it works out very nicely. Before I try it on my KT, has anyone already tried it?

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No luck here, I have 2 friends who ride KT, but none of them have tried that ( at least they won't tell ) 

Guy

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I have tried removing two springs and the clutch slipped in third gear or higher.

I came across an article on setting the clutch up for lightest operation which said to smooth the driving faces of the lugs on the plates and basket.

The factory does not bother to smooth the plate edges after stamping them out, and this wears steps in the basket lugs increasing friction.

Note make sure all the faces still touch at the same time when finished. The extra side clearance is not so important.

Also to remove excess glue from between the friction pads. This definitely improves things and gets rid of any "grabbyness" and makes the clutch give better feel.

 

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OK I have tried a few things out on my KT clutch in attempt to reduce the lever pull by reducing the pressure plate clamping force.

First I inspected the clutch and read my log book. The friction plates are genuine Kawasaki KT and about 10 years old and low hours. New genuine Kawasaki KT springs were fitted at the same time. The drive edges on the friction plate tabs were smooth. The basket fingers are steel and were smooth. The rack and pinion had a smooth action and was well lubricated. The cable is a 10 year old Venhill and was well lubed. I think I could improve on the cable by making it a bit shorter, to improve the routing. The gearbox oil is Dexron II ATF.

After that, the first thing I tried was to reduce the clamping force on the pressure plate by reducing the clutch spring preload by spacing out the spring retainer plate. I found that reducing the preload by 2mm made barely any difference to the lever pull. I also found that 2mm is about all you can add there before having to use extra clutch cover gaskets or machine something.

Next I went looking for alternative springs and found that some springs that came out of a TY175 motor were very similar to the KT springs, but a bit higher spring rate. The KT springs were 165 lb/in and the TY175 springs were 186 lb/in. This meant that six KT springs would theoretically have a clamping force of 779 lb and four TY175 springs would have a clamping force of 585 lb, or 75% of the force it had with the six KT springs. Four KT250 springs would have 66% of the clamping force of six KT springs.

I fitted four of the TY175 springs and tried it out and found it worked fine in all gears and the lever pull was noticeably less, but still not as light as my TY250 motors with their three springs. I am running very low gearing on this KT and suspect that if it had standard gearing it might have clutch slip in the upper gears.

KT 250 springs 15mm OD, 7 coils, 2mm wire, 31.5mm free length

TY175 springs 14.4mm OD, 7 coils, 2mm wire, 31.1mm free length

By the way, those springs that came out of the TY175 motor might not be standard TY175 springs

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That is really good info you have.

I have to say that I haven't gone into it as much after trying four springs.

A thought did come to mind. A lot of the effort could be in the cable because of the load times friction. reduce the load through a lever, and the spring load can remain.

Fitting a lever into the system on a KT is not easy.

I'm toying with a rod from the cable connector on the arm up through the cable mount hole (nearest to the cylinder) onto an arm, with the hinge at one end, which would connect to a bracket bolted to the outer hole. Then make the cable holding bracket attach using the cylinder mounting bolt.

Make the distance from pivot to clutch rod half the distance to the cable, half the load , twice the feel, and half the movement.

It will be quite fiddly making the brackets etc, and getting them strong enough. This will most likely still comply with the rules.

The other way is to go hydraulic, (frowned upon I suspect). To do this the easy way is to cut face off the side cover and weld thicker flat one on with bolt holes for slave cylinder from a Late model gas gas (I think), (get the oil type not break fluid type system).

Or option two; Machine out the rack system and weld a block in and bore your own cylinder into it with porting where the arm was. This option lets you choose your cylinder size and thus mechanical advantage ratio. It will also look more standard. again go oil not break fluid system, and bore from the inside, so the outside once polished will look stock. Best to have a second cover so you can go back to standard if you choose to do this.

 

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2 hours ago, still trying said:

And that folks is how you suck eggs!!

On the SWM in the photo there is still cable between the clutch and the device which would operate at full cable loading.

Your suggestion to have an intermediate lever just above the clutch cover with a rod to the clutch arm would have less friction overall than the setup on the SWM because the whole cable run would be operating at reduced loading.

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