why is mine slow?

[cals400ex]

alright i have a 400ex with just a twin air airfilter and six uni vents in my airbox lid. i have a 152 main jet in. my friend has a 400ex with a k and n with a 150 main jet in. in the 4th and 5th gears he pulls hard on me. it is really pissing me off and i don't know why. before we both rejetted mine was faster, now its not even a race because i don't have a chance. please help??? maybe i need to try a different main jet.............

[Castor-426ex]

perhaps you guys are running different gearing??

[Leo]

have you tried switching machines..?

did something screwy happen (like the shop gave you the wrong style main jet..?

Leo

it because he has a k and n, he is gettin more air flow, i have the same problem here only im winning and my friend is losing, cuz he has a uni, and i ahve k and n, k and n gives u better air flow over a foam filter:D

[cals400ex]

we both have the same gearing. also we both have the same main jet but mine is a 152 and his is a 150. they are both the correct style main jets. we went up there the same day. the dealer already gave us the wrong ones twice and i did not realize it until i had the carb off. yes he does have a k and n but he also has an outerwear on. i have a modded air box lid though. i would think a modded lid with a twin air would give more air than a stock lid with a k and n with outerwear, but i really don't know. its weird because i beat him until about 4th gear. arrrrrrrrr.....

[Stunz]

Did you ever adjust your throttle?

Chances are it's not opening all the way.

Check it out!

[NacsRacing400]

A 152 main seems high for that, Curtis Sparks recomends a 152 if you have a slip on pipe and all of the mods you listed. His jeting might be alittle more on giving some more power to because i have a k and n and it isnt that much of a ifeerence over stock.

[cals400ex]

yes we both have our throttle cables adjusted. we have no modifications to our pipes either. choke is still in place on both quads also. i was wondering if a 152 is a bit high also. i would think it would cut out at full throttle if it was too rich though? the plug also seems to be a nice tan color. thanks for the replies, any other suggestions would be great

[Wheelie]

When top end(4th and 5th gears) performance suffers after rejetting, the quad is running too rich.

Install a #150 main jet and see what happens.

[cals400ex]

sorry i forgot to mention that too, i have a 148, 150, and a 152 main jet. they all seem to give equivalent power with similar spark plug reading. this just gets confusing. any other possibilities?

[QUOTE]Originally posted by Wheelie
[B]When top end(4th and 5th gears) performance suffers after rejetting, the quad is running too rich.

very true when you change jets your engine gets a hard betting with gas and if you get bigger jets then you need to run high octan.
go to the nearest gas station and get the most exspensive gas
.plus, do you even have a aftermarket pipe because thats bad if you are running big jet and an aftermarket filter without a aftermarket pipe. and a pipe would help you the most.

[cals400ex]

every tank of gas i have ever put in is premium(which is 92 octane here). no i don't have a pipe. i just have the twin air airfilter and a modded lid.

[Big - D Racing]

The k&n flow a lot better, with a pre filter. It tears your uni apart in terms of the amount of air flow it is taking even with holes in your lid and none in his. Take off your lid completely. Unless your riding in mudd and rain keep it off, that will help a little. Go to a k &n with a prefilter. I only use a uni foam filter if riding in the dunes where there is a lot of real fine dust. That is your problem nothing else. His bike just breathes better.