I missed the clutch part of your Pm (if I'm not mixed up this morning).Thanks guys, I will have to try this, as this is a recent thing. I have not adjusted the clutch cable since I had to redo the pawl spring (for the umpteenth time), so I will try that first. As Teddy said, I don't think it would be the splines, as I have just taken that apart and lubed everything. I've never replaced a clutch, is there anything else I should look at while I am in there?
Before you open the clutch case, make sure you have the correct oil. Know what type of oil is in there. The wrong oil slips the clutch every time.
With the right oil in it and still slipping after some warmups, check the "clutch arm" at the bevel gear, make sure the gap aligns with the mark on the case as close as possible.
Next, check the fine cable adjustment at the hand lever. Free play should be about the width of a nickel - 5 cents - between the lever and the perch (see manual).
Make fine adjustments slowly, test, retest. It's a fine line between slipping and harsh shifting into 1st gear. If the fine adjustment seems wrong, thread the fine adjustment all the way in, then take up some slack at the coarse adjustment at the midpoint of the cable run. Then go back to the fine adjustment.
Mine slipped because of the oil, some Valvoline "energy saving" crap. No bueno in fun machines,. Rotella T 15W40 conventional has been in my bike since, most all oils suggested in the forum are good., syntheteic, etc. There's oil code on the bottle, what is it guys? Im birdbrained.
I did the fine adjustment before the oil, so I had to go back and adjust. A few blocks and three stops, she was fine after a good warmup with the right oil. If it slipped I adjusted the cable looser/more play, if it gnashed into 1st gear or pulled at a stop, I made the cable pull tighter/farther. 1/4 turn, then cut down to 1/8 turns or even 1/16 turn, a fine adjustment.
Do the adjusting warm, fully warm. But don't burn the clutch to warm it up.