ref to ron & jeting in general. i have been reading your posts about your jeting proplems and will add my .02 worth. i have 00wr, yz timing, yz pipe, yz throttle stop. 45/175, stk needle & pos. mix screw 1 1/8 turns. i have set this up using the yam exhaust gas analyser. i tried a 48 and the analyser was peged out rich. also i had symptoms like ron. it turned out that the spark plug was fouling out. i put in a 45 and it ran worse. a partly fouled plug will only run rite on a rich mix. then it dies. if you try a jet change you must do it on a fresh clean plug. the 45 ran perfect with a new plug. FYI best mix screw settings on ega were 2 1/2 w 42, 1 1/8 w 45, 1/8 w 48. the biggest prob with jetting the wr400 seems to be that it will run good with almost any jetting up to filthy rich untill the plug starts to foul, then no jetting in the world will make it right.