"Cleaning" a wet clutch

[CheezWhiz]

Just bought a 92 Nighthawk 750, about 20k miles on it. The owner had recently changed the oil. I noticed some high-rpm clutch slip, only when you are really banging on it. Apparently this bike is a little more difficult to change the clutch on than your average Japanese standard, so I'd like to try changing the oil first in the hopes that maybe the guy just put some 5w-30 car oil in there or something.

So the question is - I was going to go with Rotella 15w-40 dino oil, run for a bit and then change the oil again. Is there anything I can add to the Rotella to "clean" the clutch plates? Like Sea Foam, Marvel Mystery oil, eye of newt, wing of bat, etc.?

 

[Steve S]

Is there an adjustment on the clutch? Does the clutch need adjusting?

 

[CheezWhiz]

Don't think so - plenty of free play at the lever. But I've got a Clymer manual on the way so I'll definitely check that out. I understand some bikes have clutches that are adjustable at the crankcase and the free play at the lever may not be relevant.

 

[Chris142]

Maybe slip the clutch some with the new oil. Don't want to smoke it but you could slip it enough to wipe off whatever you think is making it slip?

 

[CheezWhiz]

Well there is some suspicion that "friction modifiers" in car oils cause problems for wet clutches. I'm just curious if there is anything I could or should add to the Rotella that would help get these "friction modifiers" off of my clutch and into suspension in the Rotella so they would come out when I drain the Rotella. I agree slipping the clutch some might help, I kind of figured just go for a ride to get the oil hot and work the clutch some.

 

[road_rascal]

Seeing as I have a '97 (same thing as a '92) I would change the oil (Rotella 15w/40 is fine), make sure the clutch cable is properly adjusted (I'll have to dig out the shop manuals for a number), and replace the clutch springs. I highly recommend K&G Clutch Factory springs, and they're a breeze to change out. I doubt the plates are glazed. You need a special clutch tool since these bikes have an inverted clutch basket (no big deal really). I have over 60,000 on my Nighthawk and I replaced the springs at 30K or so.

 

[CheezWhiz]

Yeah not knowing much about the subject but I doubt the plates are glazed too. The clutch holds fine except for when I'm really wailing on it.

 

[road_rascal]

Originally Posted By: CheezWhiz
Yeah not knowing much about the subject but I doubt the plates are glazed too. The clutch holds fine except for when I'm really wailing on it.


This is where new clutch springs would help. I honestly never rev this bike past 7500-8000rpms. No real point in it as you're past the torque and hp curves (more noise than acceleration). These engines are extremely durable- you should get at least 100K out of it. How's the tach working? That's the only weak spot in the early Nighthawks.

 

[CheezWhiz]

Tach works like a charm. Did the carb washer mod and that really helped operation below 3k rpms. Thinking about maybe adjusting the idle screws too since still a bit cold-blooded. Love the bike, I'm not racer or an image guy just like riding. It's perfect for just that - riding.

 

[road_rascal]

I would also sync the carbs too. I haven't done anything to the carbs on my bike except sync them twice.

 

[02zx9r]

On my zx9 i was lubing the clutch cable and didnt adjust it properly so the same thing happened, i got on it and it was slipping some, revvvved real high then finally hooked up after a split second. Adjusted the cable properly and it went away. Was running the rotella 15w40 at the time.

Would running the recommended doseage of auto-rx in the oil possibly help with clean up?

 

[CheezWhiz]

I guess that would depend on whether Auto-RX or Cycle-RX would have a tendency to get the moly or whatever other stuff is on the plates into the oil so when I drain it, the moly/other modifiers come out?

 

[02zx9r]

auto-rx, cycle-tx, tranny-rx= all same product, just the amounts you use are different for the different applications.

 

[Mackelroy]

either your clutch cable is frayed and hangin, your clutch basket tangs are worn or the plates or springs, I'd inspect all 3 the 15w40 rotella is pretty high friction oil

Are you the Zx 9 that ran redline previously


btw wet clutches are self cleaning ,just keep good fresh oil in them

 

[02zx9r]

Not me, I have run rotella 15w and 5W40 and exxon superflo 20w50

not redline

 

[Cmarti]

The detergents in a diesel HDEO may do all the cleaning you need.
The 5w-40 Rotella synthetic has cleaned out crankcases of a couple old bikes and ATVs for me. Now about "cleaning" clutch plates, I just don't know.....

 

[Mackelroy]

Your post was slightly unclear on the clutch adjustment.
did you have issue prior to adjusting the clutch cable with slipping, and when you did initially inspected the cable was there any free play in the cable.

Basically ya need a few mm's of freeplay

With the oil youve been running I highly doubt any additional cleaning will do any good, your probably going to have to repair with parts.

 

[CheezWhiz]

I haven't adjusted the clutch at all, but I think it's ok - there is some play when you pull in the clutch handle before the clutch starts to release. And there is some play when you release the handle before the clutch starts to grab.

I don't think the car oil has been in there very long, the oil looks almost new. I think maybe the guy who sold it to me thought he was better off selling the bike with new-looking oil than whatever crud was in there.

I guess I'll just do the oil change, use Rotella, and see what happens, then go from there. Bike is plenty usable right now. Thanks everyone!

 

[road_rascal]

One thing I forgot to mention is to make sure the clutch lever has freeplay when you turn the handlebars from lock to lock (all the way left and right). With a 16 y/o bike I would replace the cable (just me) or at least lube the heck out of it to make sure it isn't binding.

 

[Chris142]

Let us know if the different oil makes a difference. We always have heard about Moly and slipping clutches but they are pretty rare. I run oil with Moly in my bikes and have no troubles. But mine is only a 250 so maybe it does not have enough power to slip the clutch?