2009 Nightster,bone stock with 549 miles.If I accelerate in second gear and back quickly off the throttle without pulling the clutch in the bike makes a strange whirring noise from the left front of bike.Clutch in the noise is not there.My first thought was the primary chain was too tight .I have checked the adjustment of the primary chain twice and have it set perfect.I have also checked the primary fluid level and just replaced the shift shaft seal tonight.(shift shaft seal had a minor leak)Any one else hear this noise on their Nightster?(it almost sounds like a loud sucking of air) I have never noticed the noise on any of the other three 1200 Customs that I have owned

 

No one?

 

only in second gear???

 

Good question. I will check that on the way home today from work. 27 degrees riding in this morning. CHILLY

 

Hard to tell without being there and hearing it, but it may be the primary chain jumping under engine braking. Try adjusting it again and give it less slack.