Was in a deadlock of traffic on a hill which caused engine oil to heat up and clutch now is engaging and jerking when using first gear. It's '77' Shovelhead. What should I check first?

 

is primary setup stock? in otherwords does the oil pump supply the primary? if so the excessive heatup of engine oil will prevent it from cooling the clutch causing damage to clutch pack. convert it over, very poor factory design, the oil returning from primary is unfiltered any metal pieces or junk from primary will return to motor along with the oil