August 2, 201610 yr Just picked up this bike. Seems to have a knocking / plonking sound when the revs fall after it has been revved. It doesn't get it at idle or on the increase of revs. It appears just before the revs fall close to idle after high revs. Just put new petrol in and drained old petrol out of tank. I'm just going through the bike before I take it out for its first spin. Any ideas what this knocking is ? Air mixture? Air leak ? Or mechanical noise ? Edited August 2, 201610 yr by gazzaecowarrior
August 2, 201610 yr Sounds like too lean on the air screw from the way you describe it, but diagnosing noises over the internet isn't exactly an exact science.
August 2, 201610 yr Author Sounds like too lean on the air screw from the way you describe it, but diagnosing noises over the internet isn't exactly an exact science. Thanks for your reply. That was my thought. I'm going to strip the carb and clean the air filter. What is the rough air screw and needle position for this bike ?
August 3, 201610 yr It is probably just the clutch, which all the Pro`s do it. Does it go away with the clutch pulled in?
August 3, 201610 yr Author It is probably just the clutch, which all the Pro`s do it. Does it go away with the clutch pulled in? Yes there is a lot of clutch chatter which disappears with lever pulled in. But this noise is not that.
August 3, 201610 yr A carb clean is never wrong (unless you break it ) and a good start. Using higher octane fuel might also help against this problem.
August 3, 201610 yr If its a Dellorto carb then unscrew the fuel screw half a turn and try that. If it has had a Keihin carb fitted then turn the air screw in a quarter of a turn and try that, sounds to me like its just "Pinking"....
August 3, 201610 yr Author If its a Dellorto carb then unscrew the fuel screw half a turn and try that. If it has had a Keihin carb fitted then turn the air screw in a quarter of a turn and try that, sounds to me like its just "Pinking".... Thanks for that. I will give it a go. Bike seems totally standard. What about the needle position? I'm in Cardiff so no altitude.
August 3, 201610 yr So it should have a Dellorto carb, the needle should be a D36 with clip in the next to bottom groove, so 3rd one down from the top...!
August 3, 201610 yr Author So it should have a Dellorto carb, the needle should be a D36 with clip in the next to bottom groove, so 3rd one down from the top...! Nice one. Thanks. If its the other carb what should that one be ? I'm in work sadly so cant check.
August 3, 201610 yr Author It is a dellorto. Will try the air screw and needle position over the weekend. Thanks for all your help. Hope it works. Gareth
August 4, 201610 yr Gareth, Its not an air screw on a Dellorto, its a fuel screw, turn it out to give it more fuel, turn it in the give it less fuel.... Kev
August 4, 201610 yr Author Gareth, Its not an air screw on a Dellorto, its a fuel screw, turn it out to give it more fuel, turn it in the give it less fuel.... Kev Hi kev Oh I see. So I need to screw the fuel screw it in to the end point and then unscrew half a turn. Is that right ? Gareth
August 4, 201610 yr No, just turn it out another half a turn from where it is now to stop it from pinking, clean the carb out fisrt though incase there is any dirt in there, make sure you blow the jets out....
August 4, 201610 yr Author No, just turn it out another half a turn from where it is now to stop it from pinking, clean the carb out fisrt though incase there is any dirt in there, make sure you blow the jets out.... I understand now. Thanks
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