I did the carburetor white spacer modification - thinning it down to half its thickness and turning out the idle mixture screw about 2 turns. The bike runs so much better through all revs, especially when cold and in 1st and 2nd gear. There are no loud backfires, no farting when turning it off.

However, one thing I've noted is a change of sound on deceleration - it sort of purrs and gently burps its way down the revs, which it did not used to do. It sort of sounds better actually but wonder whether it really is also very slightly backfiring on deceleration. Is that normal - should I worry about it - should I try turning the mixture screw in or out?

Larry