A buddy of mine just bought a new 2003 400ex. He doesn't have to much money left and wants to know what performance mods are going to be the best with his limited funds. He has about $400 to $500 to spend.

 

The first thing to do is to get the 400 jetted, 42 pilot and a 152 main. Get a slip on exhaust, some are good and some just make noise. The White Brothers e-series is the best you can get. Take the head pipe off and clean out the welds on the inside and this will make it run just like most of the aftermarket headpipes. With the new exhaust then change the main to a 155, you don't need the K&N jet ket. Also, the stock airfilter is good, put the UNI is better with the outerwears cover is best for dust. Get a steering stablizer and then front shocks used from e-bay. Take the airbox lid off or put some holes in it to get more air to the engine.

 

white brothers R4 pipe, 4:16 kit or new stage II cams

 

I would say the one of the best mods he could do it +2 +1 a-arms and shocks. In that price range we will have to look in ebay for something used or get an extra $250 and buy everything new ($450 for the arms and 300 for the shocks).

The reason for my suggestion is that for $500 you are not going to build a fast motor. You could buy a pipe, a k&N filter and your money is gone. You will have a little more power. But buy the suspension and you may not be the fastest in a drag race but you could rip it up at the mx track with the best for them, no stock z400, Raptor or Bashee will even come close (equal rider skill of course).

Of all the mods on my R the a-arms and shocks are by far the most noticable, it make you wonder why they didn't come like this from the factory.

 

Thanks for all the help. This will give him an idea of what he needs to do.

 

Or for that much you could get a cam and piston and really get some more hp. Hmm.... pipe.... or cam and piston.... not a hard choice for me.

 

Hmmm - shouldn't you check and see what type of riding he's going to do before you start suggesting mods? Depending on the what you want to do, you can improve suspension, low end power, high end power, etc - but a LOT of what you do depends on where you're gonna be riding.

There isn't one 'proper' mod or starting point - you need to tailor your bike for what YOU want it to do. . .