mike0chek Posted October 11, 2011 Report Share Posted October 11, 2011 (edited) just getting my new 421 dialed in and am getting close. there is a midrange stumble that i just cant get rid of. sorry but stumble is closest thing to describing lol. its a fully drag ported 421 block with shearer SB inframes, dual pingle valve, POD'S, 24 cc domes on 93 oct., 35mm carbs with 52 pilots and 168 mains. bike idles great after dropping pilots from 68 to 52 i think, really screams on topend but hesitates right before powerband. any input appreciated! Edited October 11, 2011 by mike0chek Quote Link to comment Share on other sites More sharing options...
mike0chek Posted October 11, 2011 Author Report Share Posted October 11, 2011 o and the clip is on groove 4 from the largest end, if i lean the needle more than that it seems to rob the topend a bit Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted October 11, 2011 Report Share Posted October 11, 2011 o and the clip is on groove 4 from the largest end, if i lean the needle more than that it seems to rob the topend a bit Then lean the needle out and up your main jet one size. Quote Link to comment Share on other sites More sharing options...
mike0chek Posted October 11, 2011 Author Report Share Posted October 11, 2011 Then lean the needle out and up your main jet one size. ill have to order some jets 168 is the biggest i have, what mains you running on your 421? Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted October 11, 2011 Report Share Posted October 11, 2011 I noticed you said drag ported. I've ridden drag ported motors and some of them literally have no nutz until the powerband. Anyway, Your best bet is to plug chop your way to happiness. The needle should not affect wide open throttle... 99.9%main jet and the rest is the idle circuit feeding the engine at WOT. If you are at part throttle when the hesitation occurs you need to adjust your needles or swap out for a different style needle. If it stumbles or hesitates when you open the throttle all the way, then it is an incorrect main jet. Either way, do a plug chop. That is your number one clue. Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted October 11, 2011 Report Share Posted October 11, 2011 ill have to order some jets 168 is the biggest i have, what mains you running on your 421? 48 pilot, 160 main, CEL needles middle clip. I would imagine you would require more fuel than I. Quote Link to comment Share on other sites More sharing options...
mike0chek Posted October 11, 2011 Author Report Share Posted October 11, 2011 ok thanks for the help man, i can feel the lack of balls your speaking of down low but this really cuts out so ill have to try a bigger main and do some chops Quote Link to comment Share on other sites More sharing options...
gotta_goatsfast Posted October 11, 2011 Report Share Posted October 11, 2011 ok thanks for the help man, i can feel the lack of balls your speaking of down low but this really cuts out so ill have to try a bigger main and do some chops I wouldn't go changing mains until you know what you're dealing with. Buy a hand full of plugs and start with what you have. Then go up or down using your results. Quote Link to comment Share on other sites More sharing options...
mike0chek Posted October 11, 2011 Author Report Share Posted October 11, 2011 my plugs look great right now, i might try playing with the air screws next, i got them 2 turns out now Quote Link to comment Share on other sites More sharing options...
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