mod question

[SHARPMACHINE]

hello everyone,


I am new here and am probably asking a repeat question, but please help me out. I just bought a 2001 400ex with a white boy slip on that is otherwise stock, and I want to add some power, but not make it a racer. This quad is used for riding around the house, some trails, and silver lake sand dunes (I live 15 minutes away). I will prob. ad an air filter and mod my air box first.

I have read about jetting, a curtis advance key, a stage 1 cam, and a rev box. Have I missed anything? What order should I do mods and/or should all of these be included. I don't plan on doing a 416 or 450 kit yet, but who knows.

What about the 42 pilot jet for cold starts? Can it be left in all year ( I live in West Michigan)?


thanks alot for your help in advance :cool:

[250EXking]

Doing anthing like opening up the air supply with a modded box, and jetting is going to give you power. Try riding like that, you probably wont need the new Cdi box. But if you did the cam, you might need the new Cdi. All that is good, and not to expensive and that will get you some good power. Also, if you have someone around the does engine work, look into a high compression, standard bore piston with oversized valves and port and polish the head. My buddy has that on his 400. It rips. Just some ideas for a lot more power without spending tons of money.:)

[SHARPMACHINE]

ok, thank-you,



Anyone else have some thoughts. Any help is much appreciated.

1. I was planning on an air filter and something to allow the "lid" to breath.

2. I was hoping someone could recommend carb adjustments for this set up.

3. If I install a 42 pilot, can it be left in all year. (I was really wanting to make a year around set-up cuz I'm lazzzy :devil: and all spare time is for beer drinking).

4. Last question (sorry to drag on) I was thinking a sparks ignition key might be a good mod to do at this time??


thank you this site is :cool:

[BT&D]

I use my 400ex for working around the house, trails and dunes also. I took the lid off the air box, K&N filter with outerware, full Yoshi exhaust, 160 main jet, 42 pilot. This setup works very good in the dunes compared to stock.

[BLEEDRED]

If I install a 42 pilot, can it be left in all year. (I was really wanting to make a year around set-up cuz I'm lazzzy and all spare time is for beer drinking).

I live and ride in Michigan and I leave my 42 pilot in all year.

[SHARPMACHINE]

thanks for the replies.


For the last week I have been searching and reading info here and have decided to start with a 155 main (650' above sea level) and a 42 pilot so that it may start better. This will be done at the same time as I install a better air filter and remove my lid.

I am also trying to find a good place to order an ignition advance key (can't get one locally).

Any continued help will be much appreciated. :cool:

[400exnac]

BT&D...WHere abouts in GR are you from? Im from Comstock Park. Are youi going to make it to silver opening day or weekend?