WEnt cruising at 55-65 mph for 70 miles today, did a plug chop and the plugs were somewhat sooty. Running NARKED, 140 mains, thruxton needles, no shims. Seems a 140 is already smaller than most NARKS use, so I need advice here. THe bike came with dynojet needles. Should I put them back in and put the clip up a notch, or buy stock needles? I estimated I got about 50mpg on the run.