I had a problem with the starter clutch slipping that was caused by using car oil with friction modifiers. I was sure it wouldn't hurt the clutch as it had in my bigger engine bike.... and I was right. It didn't hurt the transmission clutch at all. But the starter began slipping.

It would slip and then catch again harshly. I was sure that it was a mechanical problem but then weighed how the starter clutch functions, the claims for the modifiers, and decided it would be worth a try to change the oil. I had no great hopes, just figured it was worth a try before to tear into it. I changed the oil to motorcycle oil and it cleared up after several starts.

That was over 10,000 miles ago. Might be worth a try... and a warning to those who get tempted to try it.
I'm old enough that I was around before this stuff was an issue. I ran MANY miles on good old engine oil like Castrol GTX and such and never had any problems. And if mileages into the 150,000+ range is any indicator, with great success. Then came the modifiers.
I still run regular old GTX in my '86 Gold Wing and have never had any problems, modifiers and all. On my CBR-1000F it caused transmission clutch problems. Thinking I understood the issue with the 1000, knowing that the engine was fairly torqey and the clutch fairly light in feel, therefore clamping force, I considered that to be an odd case with the reasons understood. Then came the EX situation. Now I just run motorcycle oil and don't have any problems. Might be worth a try... and let us know the results, please.
