If you got the motor in the UK it is 99% sure to have the long LSN.
Easy to check - Pull the throttle slide fully open to the far side of the carb throat. If the tapered tip of the LSN is still just in the spray bar, you have the long LSN.
If the needle has a rounded ¨bull nosed¨ tip and is well out of the spray bar at WOT (coming out of the spray bar at around 1/2 to 3/4 throttle), then you have the short LSN.
Sounds like you may have fallen into the age old wide idle gap, rich bottom, lean top tuning dilema.
The motor will run ok, with plenty of smoke through most of the rev range, but will be very lean at the very top. This is probably why you are buring and blowing plugs. The motor runs ok because the wide idle gap disguises the overly rich bottom end and allows the motor to function ¨almost normally¨.
Go here
http://go-racing.vpweb.co.nz/Tech-Tips.html
Scroll down to the tuning guide. This tells you exactly how to set the idle gap, lsn, and hsn correctly on the long needle GO motors. Follow this and you will be sweet.
I would say you will find your idle gap is too wide by quite a bit.
Long lsn needle settings - within 1/4 of a turn are normally:
HSN 2 - 3 ¨HOURS¨ only in from flush. Any more and you will be in trouble with lean bog etc if the rest of the carb is tuned correctly.
LSN 1 1/2 - 1 3/4 TURNS in from flush, depending on fuel, pipe and ambient conditions.
Let us know how you get on
