Clutch pressure plate travel?

[johnnyc14]

I finally got the parts to rebuild the clutch master and slave cylinders that I got from a scrapped 95 Kawasaki ZX9. I measured the clutch pressure plate travel with a dial indicator and it's got .080"-.085"

Has anybody else measured theirs with either the stock system or after a hydraulic conversion? It seems like this should be sufficient travel to provide good clutch operation.

 

[5twins]

Yes, I measured my stock set-up and only got about .061", so you should be fine. In fact, you'll probably be better off. That's one of the big problems with this clutch, not enough plate separation. That's what makes it drag and makes neutral hard to find. Just as long as it's not too much. There isn't much space under that right cover between the pressure plate an the inner side. Too much movement will result in this .....

 

[Oddjob]

5twins any idea how much is too much... a site search on the desired travel amount seems to give varying figures...

 

[5twins]

There's about 3.4 to 5.4mm of clearance depending on the year of the cover. Later covers w/ the oil sight glass have more, older covers less. I think you'd have a hard time getting the plates to separate much more than 3mm. That's twice what stock gives. But it would be nice to find an easy way to do it. That could solve lots of the 650 clutch's problems.

 

[retiredgentleman]

I modified the operating arm on my worm gear, to get more plate separation. My stock set up was giving me 0.053". With a second hole, drilled closer to the centre of the worm gear, I now get 0.073". No problem finding neutral with a hot engine.

0.080" to 0.085" movement should work very well.

Edited on Mar 22/17 to correct the numbers.

 

[MaxPete]

Agreed - too much travel would over-stress the springs needlessly. You sure are going to have a nice ride there Johnny!

Oddly, despite the fact that I got her with a seized clutch and all I've done since freeing it up by changing the cable and the engine oil and doing "Fred Flintstones" all over the garage, Lucille ('76 C-model), has excellent clutch action and finding neutral is as easy as on any bike I've ever owned. My '75 B-model sure wasn't as good as this when I rode it back in the '70s.

 

[Oddjob]

Here's another newbie question... does pressure plate travel/separation equal the linear displacement of the actuator, irrespective of method used (worm gear or hydraulic slave)... thx

 

[retiredgentleman]

Here's another newbie question... does pressure plate travel/separation equal the linear displacement of the actuator, irrespective of method used (worm gear or hydraulic slave)... thx

Well, yes it does. You're just pushing on ball bearings and push rod(s) to the clutch itself.

Edit: Of course it depends on how much free play exists, before the worm gear actuator
and ball, or the slave actuator contacts the push rod. Therefore the actuator side will show
slightly more movement than the pressure plate.

 

[MaxPete]

Agreed. The wrinkle is that there are half a dozen friction plates sandwiched among about 5 (I think) steel plates and the ideal thing would be if the total displacement could be distributed equally among all of those clutch plates. Unfortunately, with Murphy in the co-pilots seat, there will possibly some discs that stick together.

There's actually a lot more going on in there than meets the eye.

Pete

 

[johnnyc14]

The Kawasaki master cylinder has a 4 position adjustable lever. I measured the .080" travel in the #1 position which put the lever closest to the handlebar. With the adjuster at 4 I get just over .100" of pressure plate travel. Sounds like it should be good.

 

[MaxPete]

Cool!

 

[TwoManyXS1Bs]

The video in this post shows my actuator travel and pressure plate travel:

http://www.xs650.com/threads/xs650-clutch-worm-actuator-experiment-tidbits.31554/page-11#post-470442


I had installed thicker palmswell handgrips at that time, which reduced the clutch lever pull, producing that 0.040" of pressure plate travel.

Later, I replaced my 'ultimate' clutch worm gadget with the modified MikesXS worm, using the 1.2" clevis hole. Now have 0.058" actuator travel and 0.050" pressure plate travel.

Edit: A warning about excessive pressure plate travel. The pressure plate has splined notches that engage the hub's splines, so it can transmit torque to the hub. Moved outboard too far, and there's the risk of those splines uncoupling...

 

[retiredgentleman]

Agreed. The wrinkle is that there are half a dozen friction plates sandwiched among about 5 (I think) steel plates and the ideal thing would be if the total displacement could be distributed equally among all of those clutch plates. Unfortunately, with Murphy in the co-pilots seat, there will possibly some discs that stick together.

There's actually a lot more going on in there than meets the eye.

Pete

The video in this post shows my actuator travel and pressure plate travel:

http://www.xs650.com/threads/xs650-clutch-worm-actuator-experiment-tidbits.31554/page-11#post-470442


I had installed thicker palmswell handgrips at that time, which reduced the clutch lever pull, producing that 0.040" of pressure plate travel.

Later, I replaced my 'ultimate' clutch worm gadget with the modified MikesXS worm, using the 1.2" clevis hole. Now have 0.058" actuator travel and 0.050" pressure plate travel.

Edit: A warning about excessive pressure plate travel. The pressure plate has splined notches that engage the hub's splines, so it can transmit torque to the hub. Moved outboard too far, and there's the risk of those splines uncoupling...

I don't think that is possible, 2M. Those pressure plate notches look to be at least 0.250" deep. The pressure plate would be rubbing against the inside of the right engine cover, if the pressure plate travel ever got to the 0.200" area, which it can't. As 5twins said, about 3 mm or 0.117" of pressure plate travel is about the maximum that is normally possible or even desirable.
johnnyc14 should work well with the 0.100" of pressure plate travel.

 

[johnnyc14]

Thanks for all the feedback guys. Because I have short fingers I'll be leaving the adjuster in position 1 and it sounds like the .080" travel will be more than enough.

 

[TwoManyXS1Bs]

Just to clarify, for future reference.

I don't think that is possible, 2M. Those pressure plate notches look to be at least 0.250" deep...

Yes, RG, there appears to be about 1/4" of exposed spline on the clutch hub.

But, that's because you can see all the way to the steel plate. There's a 3mm friction plate overhanging that visible zone.

When you examine the hub's splines, you can see the wear/contact area of the overlapping pressure plate splines. In this pic, that's about a 3mm contact. For reference, the spacing of the steel plates' fingers are about 4.4mm (3mm friction + 1.4mm steel).

This close-up shows a better view of the pressure plate's 3mm contact patch.

The pressure plate would be rubbing against the inside of the right engine cover, if the pressure plate travel ever got to the 0.200" area, which it can't...

Folks have inadvertently assembled their clutch pressure plates with the indexing holes misaligned, causing the pressure plate to set atop the hub's splines. There's still sufficient clearance to reinstall the cover...

 

[TwoManyXS1Bs]

Another take on pressure plate travel.

There appears to be 4 zones in the clutch's personality.
1- Initial take-up, where things get compressed, and pressure on the clutch reduces, but the clutch is still engaged.
2- Feathering zone, where the clutch is slipping, but still transmitting torque.
3- Drag zone, that mysterious area where neutral can be difficult to find.
4- Clear zone, where clutch viscous drag is minimum.

This post #127 shows the zones on my clutch.

http://www.xs650.com/threads/xs650-clutch-worm-actuator-experiment-tidbits.31554/page-7#post-326482

With those zones in mind, they occupy a certain percentage of the total pressure plate travel. A large travel narrows those zones, and gives a predictable, snappy clutch feel. A small travel makes those zones seem wider, making the clutch feel mushy, but gives better control in the 'feathering' zone.

Second thing to consider is that a greater pressure plate travel requires more effort at the clutch lever. This is a significant factor when dealing with the friction-prone cable and worm actuator, since the drag factor doesn't seem to be linear, but increases exponentially as the loads increase. Not a significant factor with a hydraulic clutch...

 

[johnnyc14]

Any idea how much travel there is before the springs coil bind?

 

[MaxPete]

Any idea how much travel there is before the springs coil bind?

You can get rough idea on that dimension by simply calculating it from the diameter of the spring wire and the number of turns - and add say....5-10%.

 

[retiredgentleman]

Thanks for all the feedback guys. Because I have short fingers I'll be leaving the adjuster in position 1 and it sounds like the .080" travel will be more than enough.

I think 0.080" travel should work most of the time. It would be an interesting comparison to see how it works at 0.100".

 

[XSLeo]

I did some measuring on my 75 once. With an improvised lever mounted in place of the left engine cover. This gave me a solid lever. No cable stretch to deal with.
With right cover of, just two springs installed, I got a bit over 5 mm of travel. This was where the springs bind. With cover on no gasket, I got about 4.5 mm travel. I assume this is where the pressure plate hits the post on the side cover.
With cover off and left cover installed, so I used the cable and bar mounted lever got about 3.5 mm travel.
I had the Harley primary cover off at the same time. Using the bar mounted lever the pressure plate moved around 10 mm. Having that much plate movement on the 650 would be much nicer.
I think that would end most of our clutch issues.
Leo