I have just fitted the bosi pipe to my 300 4T and am looking for suggestions for jetting, The needle has been raised all the way, 3 1/2 turns out on mixture

Bike runs sweet through the rev range with no hesitation.

But it's running very rich will run for maybe 5 hours before fouling plug then will puff black smoke and flames on overrun after high revs.

If I replace the plug the problems solved for another 4/5 hours,

I'm confident I've no air leaks and ecu is good as I ran standard pipe today with no issues at all.

currently running 27.5 pilot, 120 main if I lower the needle I introduce a flat spot about half throttle.

Edited November 25, 201213 yr by watch this

clearly running too rich, just moving the needle down is too much so you ll need to go down on the main.. the needle should be in a mid position though so it might be as well to open up the main jet and lower the needle a fair bit.

box of jets/ needles req..