Did you put clutch in yourself? If so...there is a metal pin that holds the throwout bearing onto the fork comming from the slave cylinder...if it is not tourned the right way it will make the clutch slip when it heats up..the pin looks like it can go either way, but it needs to be turned so that the two bumps on the pin are under the two pieces that go to it on the fork..its very easy to miss...just a suggestion.