what do you know? 400 sx too a 450?

I have a 2002 400 sx, I decided to find some aftermarket parts, primarily a pipe and some other things to try and get a little more power. I have come to a conclusion that there is some stuff out there but not a wide selection too chose from, at least for a 2002 400sx so MY question is this: are the engine blocks and inner workings the same on 2003 and newer, if so would it be a good idea to change the piston and connecting rod and etc? so that I could just look for 2003 parts? I have thought about a big bore kit but that still leaves me with this question, after the big bore kit, they don't have any pipes for a 2002 450sx? would i just run a newer 450 pipe and would the frame bolts line up? please any tips or advice company names etc.


the simplest (and probably less expensive) approach would be to get the 453 kit. i also have installed a thunder alley pipe (off road-spark arrestor type) and really like it.


The 400 pipe is the same as the 520 pipe. The head/pipe connection changed in '04 and the sx's changed in '03 so you would need a pipe from an '03 or earlier e/mxc or a '02 and earlier sx. Also a pipe in itself will not give you more power. it may make more power in certain RPM ranges but IMHO it won't give the kind of gains you are looking for.

The bottom end on your bike is the same basic botom end as all the RFS motors. In order to update your motor to an 03 or later 450sx you will need crank, piston, gaskets, cylinder, cam chain and cam.

I have a 453 kit avalible that is a bolt on kit and if you add a 450sx cam you will have almost the same power as the '03+ 450sx's. Do a search here and on KTMTalk in the 4 sroke section for "453 kits" and you will find many happy riders.

If you would like to discuss options for your bike you can pm me or call me @661-713-4295


thanks Travis, What about an ignition box

What kind of power are you looking for? The '05 sx box will fit on your bike and it does make a difference. More power off idle and pulls better through the mid and about the same on top. If you want to get really fancy try a vortex ign. It has 10 different power curves to chose from so you can dial in or out power accorting to track/trail conditions

I have a 02 400mxc and I but a white brothers r4 pipe and jetted it. the guy who had it before but everything off of the 450 engine on it, He said it bolted right up. So its really a 450

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now