Knock at 3500 RPM

[Yamaharacerx]

Hey, so not sure what it is.

So when i am riding right at 3500 rpm there is a knock/ hiccup. i can feel it, like really feel it but the bike runs really good besides that. All the way through the rpm range and it won't do it all the time just when i am cruising. If i rev the bike up through 3500 it doesn't do it.

It almost sounds like a sticking valve thing but ducati's don't use springs so.....

o its a 01 900 SIE

Thanks for looking,