TOPIC:

I have a '79 KZ650B that has recently started to have some issue with the clutch slipping whenever I give it the throttle hard in low RPM. I assume, from researching, it is the clutch pressure plates that need to be replaced.

I haven't pulled it apart, but from what I can tell, is there no divider plate? Like the steel plate between the friction plate? 

When looking for a clutch kit, it only comes with the friction pieces, but no steel? IS anyone able to verify that the '79 KZ650B requires steel plates? From the looks of this: www.bikebandit.com/oem-parts/1979-kawasa...ch/o/m150610sch92031, it seems so.

I just want to make sure I order all of the parts at once. 

Hello Pyrotechx
Have you try to adjust the clutch cable slack and mechanism under the front sprocket cover first?

There are steel plates between each of the fibers.  You can download a copy of the factory Kawasaki manual here where information like this can be reviewed...www.zedrider.co.uk/service--owners-manuals.html

Many times a slipping clutch can be fixed by replacing the old clutch springs with new OEM parts.  If you get aftermarket clutch springs the hand effort will be higher so beware.  Sometimes the original plates petrify if the engine lived a hard life, and sometimes again the old plates (fibers) wear down.  It's somewhat rare for them to be worn down below the service limit but it does happen.  To measure is to know about the thickness but the increase in hardness is not measurable.  At any rate, open the clutch and measure the plate thickness and install new OEM springs and plates as needed is the first step.  If the plates measure up, replace the springs only at first and see what happens.  You can always get new plates if that doesn't work.  It only costs you a gasket.

Oh, and be sure to not use oil labeled as "energy conserving".  Car oils sometimes are labeled such.  If in doubt get some motorcycle oil or diesel engine oil.  These oils won't hurt your clutch.

Pay special attention to Nessism's advice regarding oil. 

Most car oil will ruin the clutch plates because it uses moly as a friction reducer.  Motorcycle and some diesel oils use zinc phosphorus compounds (ZDDP), but since ZDDP is not good for catalytic converters it was reduced or removed from car oils.  The way to tell the difference in the oils is very simple.  Any oil that has been tested and certified for use with motorcycle wet clutches will have "JASO-MA" marked on the container.  I would not recommend using any oil that does not have that on the label.  Ed

650ed wrote: Pay special attention to Nessism's advice regarding oil. 

Most car oil will ruin the clutch plates because it uses moly as a friction reducer.  Motorcycle and some diesel oils use zinc phosphorus compounds (ZDDP), but since ZDDP is not good for catalytic converters it was reduced or removed from car oils.  The way to tell the difference in the oils is very simple.  Any oil that has been tested and certified for use with motorcycle wet clutches will have "JASO-MA" marked on the container.  I would not recommend using any oil that does not have that on the label.  Ed

Ed,
There is much silliness surrounding what oils to use and we must be careful to not spread any misinformation otherwise we are just spreading nuts for the squirrels to eat.

Pretty much ALL motor oils contain ZDDP.  The question is how much?  Car oils use less, but ZDDP in motorcycle oils, and even diesel oils, have been significantly reduced as well through mandate by the governing bodies that control such things.  Reason being ZDDP reduces catalytic converter life when used in high doses.

The auto oils that wreck havoc on wet clutches are "energy conserving" oils.  This is an oil classification and will show in a small circle located on the oil package.  These oils are thin oils; typically 5W-30 or thinner.  If someone buys 10W-40 auto oil it won't be energy conserving and it's unlikely to damage your clutch.  You never know though.  Best stay away from auto oils entirely unless you have specific info that they are safe.  For example,  Mobil One 15W-50 silver cap auto oil is almost legion with many bikers and I've never heard of anyone damaging a clutch because of it's use.

Regarding MA oils, yes, they are certified safe for your clutch.  Most diesel oils are not MA certified though and those are safe for your clutch too so MA is NOT a mandate in my view as long as you are properly selective.  

Lastly, clutch springs spend 100% of their life in compression and after a few decades they lose some of their tension.  A new set of OEM springs goes a long way towards eliminating clutch slippage.  I'd venture to say that a lot of clutch slippage that gets blamed on oil is simply the springs fault despite what some people believe.  

I don't disagree with your points, but for anyone not familiar with the ingredients in motor oils the easiest and maybe safest bet is to stick with oils that have JASO-MA on the label.   Regarding diesel motor oil - Shell Rotella T4 has been tested to meet JASO-MA standards and is sold at most auto stores at a reasonable price, so it is not a bad choice.  Ed

On top of what everyone else said, did you replace the oil recently?  If so make sure you didn't top it off to the very top line or higher.  Too much oil can cause minor slipping to start (I think the manual may even have a warning for this).

Nessism wrote:

650ed wrote: Pay special attention to Nessism's advice regarding oil. 

[snip] Ed

Ed,
There is much silliness surrounding what oils to use and we must be careful to not spread any misinformation otherwise we are just spreading nuts for the squirrels to eat.

{snip again} .  

 Haha.. spreading nuts for the squirrels to eat..  now THAT one got a laugh out of me.   Both 650Ed, and Nessism consistently give solid advice and are both correct. As far as contaminating a clutch, I am also a sinner that has used car oil for break-in, while suffering from an extreme brain fade, not even thinking about the effects on the wet clutch.  It might have been compounded by the bombardment of pay-pal debit card charges on my checking account during an "oil leak repair" that turned into a top end overhaul complete with special square OEM o-rings, viton valve seals, Nippon piston rings and a $30.00 cylinder base gasket, that refused to come off the cases. 

 Definetly buy OEM clutch springs, or if you want to skip the left handed stress ball exercises, you can up the spring pressure with some stiffer aftermarket springs. It does make the clutch lever harder to pull. Your choice. I bought some K&L aftermarket springs, and now regret that one (as usual). I plan on locating some NOS OEM springs and soaking my plates again soon. This monster comes on like a freight train and the clutch can't handle the HP at times. 

Lots of GOOD info on kzrider, among other sites on the net. google is your friend. Be sure to add in the search term "kzrider" to get the kzr hits to pop first. Read and enjoy.  

 This is a great article and this man obviously did his homework with checking spring weights and trying different springs. I have not read it lately (6 months ago),  so read up and learn all about clutches, oils, springs and cleaning up the clutch plates after contamination. 

kzrider.com/forum/2-engine/367700-refurbishing-your-clutch

 This pic is after I soaked the plates in the ZEP citrus degreaser for ~ an hour, then did a light scuffing with scotchbrite. 

kzrider.com/forum/2-engine/367700-refurbishing-your-clutch

 One thing to note in the above thread. Do NOT glass bead anything inside your engine as suggested in the above post. Glass bead embeds itself into your parts, and can come loose with heat cycling the engine, and in turn ruin your bearing surfaces. The fiber plates especially will embed massive amounts of glass bead particles, then release it into the engine oil.

Possible soda blast, it you feel the need.

Nessism wrote: There are steel plates between each of the fibers.  You can download a copy of the factory Kawasaki manual here where information like this can be reviewed...www.zedrider.co.uk/service--owners-manuals.html

Many times a slipping clutch can be fixed by replacing the old clutch springs with new OEM parts.  If you get aftermarket clutch springs the hand effort will be higher so beware.  Sometimes the original plates petrify if the engine lived a hard life, and sometimes again the old plates (fibers) wear down.  It's somewhat rare for them to be worn down below the service limit but it does happen.  To measure is to know about the thickness but the increase in hardness is not measurable.  At any rate, open the clutch and measure the plate thickness and install new OEM springs and plates as needed is the first step.  If the plates measure up, replace the springs only at first and see what happens.  You can always get new plates if that doesn't work.  It only costs you a gasket.

Oh, and be sure to not use oil labeled as "energy conserving".  Car oils sometimes are labeled such.  If in doubt get some motorcycle oil or diesel engine oil.  These oils won't hurt your clutch.

Thanks for the information! I ordered some EBC springs and they will be here the 30th for me to install. I have a petcock issue that is leaking gas and my oil had gas in it, which is why I believe the issue arose in the first place. I recently replaced the oil with 10w40 Castrol: 

shop.advanceautoparts.com/p/castrol-gtx-...vD_BwE&gclsrc=aw.ds#

Hopefully when replacing the springs, I can just dump the oil into a catch and reuse it. It is brand new oil. I also replaced the oil filter. 

old_kaw wrote: kzrider.com/forum/2-engine/367700-refurbishing-your-clutch

 One thing to note in the above thread. Do NOT glass bead anything inside your engine as suggested in the above post. Glass bead embeds itself into your parts, and can come loose with heat cycling the engine, and in turn ruin your bearing surfaces. The fiber plates especially will embed massive amounts of glass bead particles, then release it into the engine oil. 

Possible soda blast, it you feel the need.

I'll measure the plates and hopefully they aren't toast. Otherwise, I will try the springs first hen order some plates if need be. 

I'd be leary of that Castrol oil.  The Advance Auto link says it meets "energy conserving" standards and that suggests it could damage your clutch.

Nessism wrote: I'd be leary of that Castrol oil.  The Advance Auto link says it meets "energy conserving" standards and that suggests it could damage your clutch.

Do you have a link for an oil I should use? What site where you checking to see that is meets energy conserving?  I really only have like, advanced auto parts and Oreilly around here.