Clutch slippage?

[Jiles]

I have read many post on this forum about slipping clutches but haven't found my answer.
I have a 1981 XS650 Special with only 5K miles on odometer ? ? Although I have no way of verifying mileage is correct, condition of bike suggest this is correct. One reason being tires are original with plenty of thread but signs of dry rot. They will be changed.
I didn't notice clutch slipping when I bought it because it was running so bad. Clutch cable was lubricated and adjusted correctly and slippage is noticed even in fifth gear accelerating up a slight hill.
I inspected all clutch friction plates and they measure a tad over 3mm with slight discoloration on some of the steel plates.
New OEM Yamaha springs measure 0ne mm longer then original.
I changed, what looked like new oil, cleaned both filters and found very little contamination.
I changed to Chevron Dello 400 15W40 because that's what I use in nearly all other small engines, along with my 1976 MGB Roadster and Kubota diesel tractor.
With what I have found, could the Dello oil be the problem?

 

[5twins]

Two things I'd try before replacing all the fiber plates is sanding the metal plates against some 220 paper to rough them up a little and then, if that didn't work, slightly stiffer aftermarket springs.

I've found the stock plates to be very robust and have rarely found any that measured worn, but there have been a couple reports of them just going bad. This wasn't from wear, they simply didn't work right anymore. There's also no telling what oil a P.O. may have put in there. If it was one of those "energy conserving" car oils with anti-friction additives, the plates may have gotten contaminated. I don't think your oil choice is at fault but it would be simple enough to try something else. Personally, I use the 20W-50 Walmart oil, cheap and has always worked fine for me.

 

[XSLeo]

Is the Dello 400 oil wet clutch compatible? If not then tat may be part of the problem. Perhaps a PO used an energy saving car oil. The energy saving car oil have friction modifiers that damage clutch plates.
While you have it apart, look at the steel plates. They are stamped out. This leaves a slightly rounded edge and one sharp edge. I use a medium grit sand paper to remove this sharp edge, round it a bit so it matches the other edge. Sand off any discoloration as well. Sanding the whole gripping surface of the steels will improve the grip.
On the fibers, you can check the edges and sand any sharp edges you find. Sanding the gripping surfaces may clean them up enough to improve their grip some too. This might remove any damage from wrong oils.
When you reassemble the clutch, using new springs is a good idea. 650centralsells three different spring strengths. Call and talk to them. He will suggest which ones to use.
If your clutch still slips after this, then you might need new fibers. 650central sells tem too. I like the Ferodo plates.
talk the then at 650central about them too.
Leo

 

[Jim]

The PDS for that oil say's it has "friction modifiers" added so.... yeah the oil might be part of your problem.

 

[XSLeo]

On the back of the jug there are a list of specs. Like on the oil use it says meets or exceeds API SF/SG/SJ and a JASO MA. This last one is the wet clutch rating. This means it was tested and approved for wet clutches. This is a motorcycle oil.
Some diesel oils have this rating, some don't.
Leo