Check the clutch release and cable adjustments and
lube the clutch cable.
To adjust the clutch release, first remove the sprocket cover on the left side of the engine. Just ahead of the front sprocket and chain, you will see the end of the clutch cable, fitted to the clutch release.
Next, look at the clutch cable, along its run beside the carbs. There should be an inline adjuster that needs to be made as short as it can. There will be a large body, a lock nut and an opposite end adjuster, Loosen the nut, turn the ends together to slack the cable. Do the same at the clutch cable adjuster at the lever holder on the handlebar. You want the clutch lever to come completely back to the handlebar without even trying to release the clutch.
Then, down at the clutch release, there will be a nut and screw. Loosen the nut, then turn the screw inwards, right hand rotation, until you just feel resistance against the screw. Stop, back the screw off 3/8ths of a turn, lock the locknut down, replace the sprocket cover.
Then, at the handlebar, make the adjuster have about two complete turns out from all the way in. The lever will still not release the clutch.
Last step, turn the inline cable adjuster down at the carbs, to give the lever on the handlebar about 1/2 inch pull from its at rest position before it starts to release the clutch. Lock the adjuster with the locknut.
Test ride, see if it still slips.
The clutch should begin to release with about 10mms
(3/8ths of an inch) of lever travel at the handlebar when the engine is at full
operating temperature, not a quarter or halfway back to the bar. As long as
there is free play in the cable, and there is 3/8ths of a turn on the adjustment
screw backed off on the release mechanism, and the clutch doesn't slip, you are
There will be a bit of free spin to the rear wheel when on the center stand and out of gear, this is normal and not a concern. You should be able to stop the tire when this is happening. I just touch the tire with a foot/shoe.
I run either straight 30 wt NON-SYNTHETIC motor oil or a good 90 wt gear oil like Sta-Lube or Torco, with NO additives.
Usually, the plates aren't bad, but the springs should be replaced, and I suggest doing what was advised in the above posts ONLY IF THE CLUTCH STILL SLIPS, check the steels, bead blast them, and check the fibers, but do not run Barnett plates, seek out a dealer with K&L Supply sources for Vesrah fiber plates, and then, use the Barnett springs.
How do the plates get wiped out? Well, one of two
reasons, either adjustment/release of the clutch isn't correct, holding the
clutch partially released, AND/OR, springs are sacked out.
In 35 years of working on all sizes of triples, I've replaced only a handful of plates, but a bunch more springs.
I'd also say that there is no way to correctly assess the clutch condition until the adjustment is correct, and after that is done, if there is still an issue, then, and only then, go for the internals of the clutch.
The adjustment should be done before any tearing into the inner workings, it may not be internal.