A short while ago my CBF250's clutch started slipping. Going uphill in high gear the revs would rise but the speed didn't. This was surprising. Although the little bike has done a fair amount of miles, bike clutches don't generally wear out. Especially since the CBF has modest power and low gearing so doesn't give the clutch a hard time.
Before proceeding further I checked the cable. The pull on the lever wasn't excessive but the cable seemed to be sticking. You can try squirting some oil down it but I thought I could do more.
I fitted a tube over the end of the cable, filled it with solvent and blew it through the cable with an air gun attached to my compressor. I then blew some chain lube through it.
Success! the clutch no longer slips. Seems that the resistance in the cable was enough to cause slippage.
|Operating arm on engine|
|Disconnect the cable at the lever....|
|....and at engine|
|...and blew through some solvent then chain lube|