I have a 2005 280, the bike ticks over nicely and revs up very cleanly but on overun it tends to pop 3 or 4 times ussally as it reaches lower revs. Its running a 118main and a 38 pilot with boysen dual stage reeds. I have checked for air leaks and have recently cleaned the exhuaust repacked the silencer and sealed the various joints but still it does it, interestingly if you rev it up and then flick the choke it dosent pop at all which makes me think its a fuel problem, the bike runs fine apart from this so am not sure if this is just something they do.

Try lowering the idle. This allows less air into the pilot circuit, if that stops it then the pilot adjustment needs to be richer. Bit of a juggling act between what idle you want, bottom end smoothness and over run pop. Does the motor rattle when you float along at a very slight throttle opening ?

Cheers ShercoH

Will definatley try that, raising the needle seems to help a bit but dosent cure it, havent noticed any rattling, but it does pop and burble at low revs but under load ie. riding up a steep hill it runs very smoothly, if it wasnt for the exhaust popping on throttle off i wouldnt know there was any problem. I have just retarded the timing a bit to hopefully smooth it out further.

lifting the needle has richened the area above the idle/pilot circuit. What small improvement it makes is due to the extra fuel residually left after opening.You need to adjust the idle circuit as that controlls when the slide is fully closed. Don`t recommend you change ignition from factory specs,while chasing this. Change one thing at a time.