Clutch started slipping at high RPM

[coughing skunk]

I think it is time to re-do the clutch plates, but figured I'd put the feelers out in case anyone can tell my I'm being an idiot.

To recap, I've been having this issue since I first got the bike but lately it has gotten worse. When I'm goosin it, my clutch will slip once I get to a high RPM (no tach, couldn't tell you how high). If I cut the throttle, the clutch grabs again and I typically shift to the next gear. When the clutch slips it just goes and the engine over revs hard. I feel the clutch used to hold on longer before it would slip and recently the slip point has dropped. I replaced the worm gear spring with a stronger one as my old one was dead. I also replaced the clutch springs with the 'high performance' ones from Mikes. Aside from making the clutch pull feel better, it seems that there was no effect on the slipping. The clutch is adjusted correctly, etc. I had Hughs hydro clutch on my bike for a while, but it was causing more grief the longer it was on so I finally switched back to the stock cable puller.

More recently, the clutch has been slow to grab gears when bangin through em. It feels almost rubber band like. I'll shift and let out the clutch, get back on the throttle and the clutch engages but then stays at a constant RPM for a second before it starts pulling again. This is not how the bike has behaved the past year of riding, and there has been no significant changes (minor carb adjustment and some electrical work).

I don't believe that it is the oil I'm using, as I'm using Lucas 20w50 moto oil and have for the life of the bike.

All that being said, am I'm looking at a clutch overhaul? If so, should I do the extra plate upgrade?

 

[coughing skunk]

bump to the top for some better visibility

 

[weekendrider]

I haven't ever heard anyone proclaim Mikes springs(even the performance) were worth it. You may want to look at the springs 650 central sells first.

 

[5twins]

Yes, the springs from Mike's aren't very good. The set I got measured 45mm long new, 5K later they had already sacked to just under 43mm. Now, a few years later, I can feel the clutch slipping occasionally. I'll be swapping them out this season some time for a real brand name set from 650Central. Check yours to see if they're sacked.

If it hasn't been swapped out then you would have the old style 6 plate clutch with the thicker frictions and rubber rings between the plates. The frictions appear to still be available but not the rubber rings. However, even discounted, the plates are like $25 each. That would run you $150 to replace them. Of course, measure the thickness first, they may be fine. If they are worn out, a better, cheaper option would be to swap in a whole newer clutch assembly. I would recommend the last style produced from about 1980 on, the 6 plate unit with the dampened bottom steel plate. I feel these were the best 650 clutches. That spring-loaded bottom plate makes them engage smoother, especially when taking off in 1st. They're also easier on the little coil cush springs on the back of the main hub. If you watch eBay, you should be able to pick up a complete unit for $30 or $40.

 

[coughing skunk]

Oh bummer on the springs. I'll keep an eye out for the newer style clutch assembly and live with the slippage until the next oil change. This bike is *mostly* a bar hopper and doesn't see any extended use, so it isn't a real big deal. I'd just rather fix this sooner than later.

On the bright side, I just finished rebuilding the motor on a 70 CL100 so I least I've got that goin for me.

 

[teamkandy]

It is the Lucas 20w 50w oil. I had the same problem with LUCAS oil. I had new EBC springs and no name fiber plates from ebay. I scratched my head and looked up the oil I had used and found this on the LUCAS oil site. If you read it says "Lucas High Performance 4T Motorcycle Oil WITH MOLY is designed for NON WET APPLICATIONS". http://www.lucasoil.com/products/display_products.sd?iid=288&catid=16&loc=show I guessed the Moly they have in the oil impregnated the clutch fibers. I tried running a couple changes threw with Rotella late last fall but it still slipped on 5th gear throttle roll ons or hard acceleration. so I bought another new set of EBC fiber plates and am now running 20W 50W Castrol motorcycle oil from the parts store that says on the back of it is ok for wet clutches.

 

[XSLeo]

I like the Ferodo plates, I think it was about $45 to $50 bucks for a set of seven plates. They sell them that way so you can use the same set in either the 6 or seven plate clutches.
On your 73 you can take out the 6 plates and the rubber rings and put in the 7 of the later thinner plates, you just need one more steel.
I also got a set of Kibble White 70 lbs springs. When apart use coarse sand paper, like 120 or 100 grit to clean any discoloration off the steels. The steels are stamped out of sheets. This makes one edge slightly rounded, the other slightly sharp. While sanding the color off sand off this sharp edge. This lets the steels slide in the basket easier.
Leo

 

[weekendrider]

It is the Lucas 20w 50w oil. I had the same problem with LUCAS oil. I had new EBC springs and no name fiber plates from ebay. I scratched my head and looked up the oil I had used and found this on the LUCAS oil site. If you read it says "Lucas High Performance 4T Motorcycle Oil WITH MOLY is designed for NON WET APPLICATIONS". http://www.lucasoil.com/products/display_products.sd?iid=288&catid=16&loc=show I guessed the Moly they have in the oil impregnated the clutch fibers. I tried running a couple changes threw with Rotella late last fall but it still slipped on 5th gear throttle roll ons or hard acceleration. so I bought another new set of EBC fiber plates and am now running 20W 50W Castrol motorcycle oil from the parts store that says on the back of it is ok for wet clutches.

Thanks for the tip off!

 

[coughing skunk]

If you read it says "Lucas High Performance 4T Motorcycle Oil WITH MOLY is designed for NON WET APPLICATIONS". http://www.lucasoil.com/products/display_products.sd?iid=288&catid=16&loc=show

Yup, that's the stuff. Looks like I'll be switching oils as well. Thanks for this bit of info

 

[teamkandy]

+1 LEO, on the sanding and cleaning up the metal plates I did that as well. I laid mine on a flat piece of glass and checked to make sure there was no warping. I got lucky all my basket fingers were in good shape. I went a head and ran a file and sand paper over them. I don't think it was required but my dad always had me do that to my MX bikes and it seamed to always make my clutch working smoothly.