hey everyone im hear to ask wat u guys put on ur 400ex as first performance upgrades and if anyone had any suggestions on wat to get first for my first upgrad and how much it would cost thanks everyone

 

On my 400ex i added a DMC afterburner full exhaust, JE 12:1 high compression piston,CDI rev box, K&N power lid, uni air filter, uni pre filters, Custom jets and needles. That cost me rite around 1,000 dollars.

I would say if you dont want to spend any money i would just uncork it by removing the end cap off the exhaust and taking the air box lid off.

But if you wanna spend some money probally would be best off by getting a exhaust system and re-jetting your bike, also you could just get a Procom cdi rev box it is only about $100 and it adds 1200 rpm's and 5 horspower at the top end and takes about 30 seconds to install

 

thanks so when u put on all those things did u feel a ig gain also i posted a topic about removing the airbox lid and got a reply saing that it would be a good idea unless i reletted it but if i did take the silencer off and the air box lid ff wold i really feel a gain or would it gust lessen me engine life because ofteh air box lid is off

 

If you ride in dusty conditions, it will require more filter maintanance, but it you ride in creeks and stuff I would not remove the air box lid as it will make it easier to let water in.

 

If you take your air box lid off you will get a lot more air and your bike will run very lean. you would have to buy some jets and rejet it until its right. i you did that you would be able to feel a pretty good power gain.

 

i noticed huge power gains mostly in the bottom and mid range rpm's tons of torque.
I can tell so much because my sister has a bone stock 400ex and i ride hers in my backyard and street alot because its not loud and mine is way to loud.

But yeah just by taking the airbox lid off and removing the end cap off the exhaust you will definitely notice a power difference basically you allowing your machine to breeth uncorking it. But you will also probally have to get a larger main jet cause your bike might bog down a little to balance out the air - fuel cost you like 5 bucks if even and takes you like half hour to install. Also by uncorking it it is better for your engine

 

Jets are cheap i opened mine up and we didnt have a jet big enough or it so i had to mod. the cover instead. Jets are really simple to put in all it6 takes is a 17mm wrech to take the plug out of the carb and a 1/4 inch socket on a swivel to take your jet out and reinstall.

 

ok sounds about right but if i got new jets for it isnt there like 10 different sizes because MY FRIEND GOT jets for his ltz400 and he got at lease 20 different jets wat ar all them for and dosent the 400ex need more then one jet?? to get performance

 

all you need is the main jet. and there are more then 10 of them. my stock jet was a 148 and i had to jump up to a 178 with holes in my air box and slip on pipe. 178 was still to lean to take the cover off completely

 

ohh ok well i was thinin of buying some dyno jets or something soon and now u said that u have a slip on exhaust is it realy worth it the pony up the extra 1 or 2 houndred for the wholesystem or would the slip on still be good enought power gain because i read on line that a white bros e serios slip on adds up tp 4 hourses and the whole system 580dollers adds 4-7 while the slip on cost around 380