TOPIC:

I just got done wrenching on my beloved '82 GPz750.

I changed the oil last month, and put in the same boring Castrol 20w50 GTX that I've used since the time that the Earth cooled, but the bike developed a little clutch slippage - only at full power - starting at 7000-8000 rpm's, so if I really wanted to show it to you, I'd run it up to redline in 1st, it'd start slipping, and on the upshift, it'd keep slipping until I let off the gas.

So my new clutch discs & steels arrived yesterday, I found a nice clean empty ice-cream bucked, tossed them in a quart of oil, and swapped them out today. No problems on the swap - I didn't even have to change the cable adjustment.

It works super, and on a hard one-two shift I overdid it a little, and it started to launch the wheel, and lever effort is the same.

I'd still like to know why it slipped - lots of material on the plates, and the steels aren't even marked.

Any ideas ?

Slightly overfilling the oil level can cause some slipping after an oil change, when there wasn't any slippage prior to the oil change.
I just went through this on a 550.

If that was 20-50 GTX made for cars they changed the formula almost back when dirt was invented and it is not made to use in a Kaw any longer as the friction modifiers make a wet clutch slip. Others here like 650 Ed can show you lots of data, but The GTX I used 20 plus years ago is no more. Best for me is Shell Rotella diesel oil you can get at Walmart

Not sure about car oils any more. They don't say what's in them and I don't trust them. I guess you have to look for the JASO-MA tag to be safe. I do know that any oil that says "energy conserving" on the starburst label has moly in it and will ruin your clutch.

Try adjusting the clutch before changing plates,The fact you say you didn't need to change the adjustment after installing new plates is a red flag for me anyway.

Street Fighter LTD wrote: If that was 20-50 GTX made for cars they changed the formula almost back when dirt was invented and it is not made to use in a Kaw any longer as the friction modifiers make a wet clutch slip. Others here like 650 Ed can show you lots of data, but The GTX I used 20 plus years ago is no more. Best for me is Shell Rotella diesel oil you can get at Walmart

All true. The contents of car oil changed several years ago to include friction modifiers that don't damage car catalytic convertors. If the oil container does not show "JASO-MA" do not use it in your Kawasaki because it will affect the clutch - and not in a good way.

You may need to remove and scour the clutch friction disks or replace them. Ed

I had to drain the oil anyway, and being suspicious of the 'car oil' after reading here I refilled it with Castrol 15W40 diesel oil - mainly because I see the diesel oils popular here on the forum.

BTW - I went with the Barnett Kevlar discs, Barnett steels & springs too. I just got back from a ride - work great.

PLUMMEN wrote: Try adjusting the clutch before changing plates,The fact you say you didn't need to change the adjustment after installing new plates is a red flag for me anyway.

Points towards something other than friction plate wear.

Not wanting to start one of these endless oil threads, but these modern semi synths can be a problem with wet clutches. Back in the day I used anything within spec but now I am noticing the difference.

I had a similar problem on my 750, I checked friction plate thickness, wet and dry cleaned up the plain plates, solvent cleaned and then shimmed each bolt with a washer and problem solved. It might be the super slippy modern oil components only stick to metal surfaces so your 'old'clutch may be reusable?

Nice collection Eric.

Most of the clutch slipping problems I have seen are caused by the springs collapsing. Keep your old discs and steels, they are probably still in spec. Measure the old springs, the manual should have a minimum length spec.

Tyrell Corp wrote:

PLUMMEN wrote: Try adjusting the clutch before changing plates,The fact you say you didn't need to change the adjustment after installing new plates is a red flag for me anyway.

Points towards something other than friction plate wear.

Not wanting to start one of these endless oil threads, but these modern semi synths can be a problem with wet clutches. Back in the day I used anything within spec but now I am noticing the difference.

I had a similar problem on my 750, I checked friction plate thickness, wet and dry cleaned up the plain plates, solvent cleaned and then shimmed each bolt with a washer and problem solved. It might be the super slippy modern oil components only stick to metal surfaces so your 'old'clutch may be reusable?

Nice collection Eric.

Golden spectro has been around since late 70s-early 80s,never had a clutch issue with it.