gazzaecowarrior Posted August 2, 2016 Report Share Posted August 2, 2016 (edited) 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, 2016 by gazzaecowarrior Quote Link to comment Share on other sites More sharing options...
heffergm Posted August 2, 2016 Report Share Posted August 2, 2016 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. Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 2, 2016 Author Report Share Posted August 2, 2016 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 ? Quote Link to comment Share on other sites More sharing options...
lineaway Posted August 3, 2016 Report Share Posted August 3, 2016 It is probably just the clutch, which all the Pro`s do it. Does it go away with the clutch pulled in? Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 3, 2016 Author Report Share Posted August 3, 2016 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. Quote Link to comment Share on other sites More sharing options...
crazybond700 Posted August 3, 2016 Report Share Posted August 3, 2016 A carb clean is never wrong (unless you break it ) and a good start. Using higher octane fuel might also help against this problem. Quote Link to comment Share on other sites More sharing options...
fullfactorykev Posted August 3, 2016 Report Share Posted August 3, 2016 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".... Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 3, 2016 Author Report Share Posted August 3, 2016 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. Quote Link to comment Share on other sites More sharing options...
fullfactorykev Posted August 3, 2016 Report Share Posted August 3, 2016 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...! Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 3, 2016 Author Report Share Posted August 3, 2016 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. Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 3, 2016 Author Report Share Posted August 3, 2016 It is a dellorto. Will try the air screw and needle position over the weekend. Thanks for all your help. Hope it works. Gareth Quote Link to comment Share on other sites More sharing options...
fullfactorykev Posted August 4, 2016 Report Share Posted August 4, 2016 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 Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 4, 2016 Author Report Share Posted August 4, 2016 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 Quote Link to comment Share on other sites More sharing options...
fullfactorykev Posted August 4, 2016 Report Share Posted August 4, 2016 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.... Quote Link to comment Share on other sites More sharing options...
gazzaecowarrior Posted August 4, 2016 Author Report Share Posted August 4, 2016 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 Quote Link to comment Share on other sites More sharing options...
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