I know I've screwed up...How bad is it?

I run Rotella 15w40 in all of my machinery, except for the Civic, which calls for 5W20.

I also run shell rotella T in everything and its the ONLY oil i will put in my kz.

Has this bike been sitting for a decade? You stated you didnt change the oil in a decade.
I have seen alot of bikes that sit have steel clutch plates that have rusted. I usually go out and hold the clutch a little open and just grind the scum off the plates letting the motor rev up. Really it works! Only take a block or two.

Grumpy Ole Artist wrote: Thanx for the encouragement! Yes, I have tried the external clutch adjustments, I believe that I performed the internal adjustment over the winter, but definitely will do it (again?)to verify...Martin, 20-50, the kind in a plastic bottle! LOL! Do they MAKE different oils? (I did attach a pic of the back of the bottle.) Thanx for the oil brands, BTW! Snapped pic to bring in, get on here, and look up the oil/clutch slippy ingredient thingie...SHO would like to find a correct pdf manual...Thanx again, all!

Some oils have friction modifiers, such as lighter weight oils & some of them will have "Energy Conserving" on the label. The additives are supposed to make them too slippery for a motorcycle's clutch (I guess?). From the label, it seems to me the GTX should have been fine, but a product data sheet says it has "Ultra-low friction to improve gas mileage" - which could be why your clutch is slipping? Conversely, the MSDS lists the ZDP as 5-10% (seems rather high ?!?!).

A lot of riders like the Mobile-1 Racing 4T 10W-40 (it's a motorcycle oil).

As for slayer's comment about the Delo, you pretty much have to keep up to date on the MSDS info for any oil. They usually list the zinc-phosphate content as a percent. Heavy duty, motorcycle, & racing oils typically have 1-2% ZDP or ZDDP.

Castrol GTX works and doesn't have friction modifiers unless you run 10W30 or lighter oil. I can't see the oil causing the clutch problem. I've even run 10W30 in very cold weather that had the friction modifiers without knowing til after a couple thousand miles and clutch never knew the difference.

See how fast this is turning into an oil thread!!

Grumpy Ole Artist wrote: Thanx haybus! What would be the procedure for cleaning the clutch discs...An aggressive solvent, such as lacquer thinner? Milder? (VM&P naptha, etc) Any abrasive? (Sandpaper, whetstone,etc) Should I "flush" Castrol residue out of the crankcase with a mild solvent? Will I need to have a replacement gasket on hand for side clutch cover, or does it come off with cover/stay on case? Sorry,I'm a Newb! Thanx, again!

I personally would use brake cleaner on the friction plates. I wouldn't flush the case with anything. What little is left of the friction modifying oil after draining will be quite diluted with the new oil. Probably need a new gasket if its been on there a long time. It will be stuck to the case, cover, or a little of both. Resist the temptation to reuse the old gasket with silicone. Once silicone is on a surface it's very hard to remove and few products, other than more silicone, will stick.

As was stated by others you could simply R&R the oil and see if it cures the problem.

Good advice to get a manual. I just figured it goes without saying. Should be a rule you cannot post here until you show proof of a factory manual.

I have ran Castrol GTX and other oils in bikes such as an 89 ZX-10 and a 99 TLS with no clutch slippage. However after reading some stories on here I went with actual motorcycle oil (Valvoline Motorcycle 4 Stroke 20W50)in the KZ and my clutch slips a bit. It could just be a worn out clutch. :blush: