400ex popping/missing?

[brad200615]

I have recently acquired a 400ex that has been bored to a 416 with a 11.1:1 piston, heads ported and polished, stage 2 cam, curtis sparks X6 pipe and was told it had a 450 carb on it but comparing to my buddy's stock carb it dosent look any different so not 100% sure on it but anyways when i am just cruising around half throttle or a little less it sounds like it is missing. thought it might be a fouled plug so changed it and still does it.
Is this normal or can anyone give me any ideas on what could be a problem.

[exrider87]

If it only does it at half throttle it sounds like your jetting is off. Probably need to adjust your needle.

[big95xj]

I bet that 200 main is a lil to much for it now that it actually has an air filter on it...when we goin to the track?

[420exJuggalo]

i know this might sound stupid,try ridin it w/yer air box lid off, if u have one on.. worked for me after i jetted my bike.

[brad200615]

currently it dosent have an airbox lid

[exrider87]

does it have a choke that you can reach on the left side of the carb? if so try choking it slightly and see if it makes it better or worse. If it makes it better you probably need to be jetted richer, worse it needs to go leaner.

[brad200615]

Well since posting I found out it had a 200 main jet and haven't gotten the chance to play with it and get it lowered

[ngarbe561]

poping and missing genral means the jet is to small not to big

[420exJuggalo]

try adjusting ur fuel screw, turn it all the way in,then back it out about 2 1/2, to 2 3/4 turns out, btw you might have a clogged jet,so pull the carb take it apart and remove your main and pilot jet, clean it, take a wire brush and pull one wire off it with some pliers, use that one wire to run in and out your jets, thru the hole in it. clean it with carb cleaner and hit it with some compressed air, put it back together and adjust your fuel screw like above, also u should run a 170-175 main and about a 38 or 40 pilot if your under 2000ft. elev.if u allerady have a 40 go to a 42, and your clip should be 3rd from top on needle. good luck

[brad200615]

well when i get my next day off work ill try these things and see what happens thanks for the info