Hi and welcome to the forum.
I had the same issue with my '03 RFS bike.
Believe it or not, it was the exhaust valves being
tight.
When did you last check the clearance?
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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)