400ex dont run good at top end

[97blaster200]

hey guys my brothers 400ex doesnt run good when u give it alot of gas. we changed the jets about 20 freaking times and it still doesnt run right! its at a stage 2 jet kit from moose. if we take the airbox boot off of it it runs AWESOME. but when we put it back on it runs like pure shat.

CAN SOMEONE GIVE ME SOME IDEAS ON WHAT TO DO?

[frankiedizzle56]

clean carb an maybe that will work

[97blaster200]

we cleaned the carb......and it still runs like shat at the top. but when we take the air box boot off its fine. and we keep trying to adjust the air/fuel intake and it still does it.

[dunes_rider]

just keep the lid off u dont need it i have my airbox lid removed and i like it.

[97blaster200]

the aibox lid is off. is some kind of aftermarket box that reloactes the battery into the box. we got something today from a local honda dealership so hopefully it will work.

[underpowered]

you are way to rich. if you take to boot off to let more air in and it runs great, that means you have too much fuel for the amout of air you are getting. what all is done to the bike mod wise, what jets have you tried, what is you air/fuel screw set at now? tell me this and i should be able to give your a rough estimate on where you should be at.

[cals400ex]

my bet is your mainjet is just too big. you could also be rich on the needle clip too...

[97blaster200]

the motor is bored to a 416. and it has a pro circuit t-4 silencer and i think header? but im not sure. it def has the silencer though. our main jet is a 170. honda dealership i talked to said that would be a good jet for the mods on it.

could it be the pilot jet? we just changed that fom a 48(stock) to a 55. they also said to do that so i duno what the problem is?

[cals400ex]

Originally posted by 97blaster200
the motor is bored to a 416. and it has a pro circuit t-4 silencer and i think header? but im not sure. it def has the silencer though. our main jet is a 170. honda dealership i talked to said that would be a good jet for the mods on it.

could it be the pilot jet? we just changed that fom a 48(stock) to a 55. they also said to do that so i duno what the problem is?


first off, the stock pilot jet is a 38. if you upgrade, get a 42 or 45. a 170 mainjet will be too big if you have the air box lid on. are we still talking about dynojets or keihin jets?

[97blaster200]

honda dealership told me the stock was 48 i thought. oh well...we are talking about dyno jets. we got them from the honda place. moose dyno jets. they dont say u have to change the pilot jet. so we went to the dealer and they told us to change it to a 55. so we did that and we did the same shat.

OH AND ALSO,

there has never been an airbox lid on it. i was talking about the snorkel

[underpowered]

the pilot is WAY To big, go down to a 42. stockis a 38, not 48. and the 170 is also too big, try a 162 or 165, needle on 2nd clip down, ir fuel screw 3-3.5 turns out. It should run better, but may still need to be messed with a little.

[shorgasm]

Just an idea here...Check the carb boot out real good.Pulling it on and off may be causeing a airleak somewhere.

Is it performing poorly off idle on the needle or the main?

[shorgasm]

Spray some carb cleaner around the boot when it runs poorly and see if the rpm's change any bit.That'll show an airleak.

[cals400ex]

i would probably start with a 42 pilot jet, 165 mainjet from the moose kit, and the moose needle in the 3rd clip position from the top. this is just starters...

[97blaster200]

thanks guys...ill be working on it all week so we'll see what happens.