Just a thought from when I was chasing down an errant "new" noise on
my 640.
Anyway, I tore off all my plastic, and tank and found a 8mm socket had
fallen between my right radiator and the frame down tube.
It had driven me mad for about 3 rides.
Not saying that is your issue, but I'd do a "sanity check" before I went
into the engine.
__________________
2011 Husaberg TE 300
2002 640 LC4e
Past Rides
'03 KTM 450 EXC (SOLD)
'01 Honda XR650R (SOLD)
'98 Honda XR600R (SOLD)
'95 KTM 620 RXC (SOLD)
'88 Yamaha TT600 (SOLD)
'86 Yamaha XT 350 (SOLD)
'84 Yamaha IT465 (STOLEN)
'83 Kawasaki KDX 450 (SOLD)
'83 Honda CB1000 Custom (SOLD)
'82 Kawasaki KDX 400 (SOLD)
'77 Yamaha DT200 (SOLD)
'70 Honda CT70 (SOLD)