mine just started doing the same thing and my buddies thruxton does it as well. i'm pretty sure it's the clutch. what oil do you use? i'm using 20-50 now and it started happening. my buddy swears his got worse when he went from 10-40 to 20-50. i also have a mechanic friend who says he come across it before, he takes the clutch all apart, everything looks fine, carefully puts it back together using the triumph aligning tool and it goes away. i'll be going back to 10-40 on my next change to see if it goes away. i'm in los angeles so it's mostly in the high 70s to low 90's.
