ktm 400 perfornance mod?

Im new to TT. I was off of a bike for years and just picked up an 01 ktm 400 exc. Was curious if there are any cheap/quick mods i can do to improve performace/ power?

what doesnt it do for you? its an old bike doing mods might not be worth it.  They do exist but mainly a 453 kit.

Well i love the bike. Has great power and feels smooth all the way through. Alrhough i used to ride when i was younger i never got into doing mods. I am just curious whats out there... What are otjers doing to improve power, response, or even gas mileage.

Other than an off-idle bog, I don't remember much bad about the 400 from that era

The best part about a 400 is that it's a 400. Nice and smooth delivery of good solid power.

Might be time for you to check into a newer 450, 350 or 500

HT Racing used to make a smaller header pipe that woke that engine up a bit, mostly on the bottom end. Rather unlikely you can find one but you might post in the wanted on ktmtalk. Replace your accelerator pump with the Honda unit in the FAQ at the top of the forum.


I put HT Racing's 453 kit in two of my 400s. That really wakes the bike up. If your bike is in very good condition it may well be worth it. The only must do thing is replace the cam gear if it hasn't been done and when the water pump starts to weep upgrade to the later model water pump seals. The old style cam gear has a nut and bolt for the decompressor versus molded in. I just tack welded them with a wire welder. The rear wheel spacers are made of putty. Replace them with the later units, your wheel bearings will last longer if you ride in a lot of water. Also look in your parts book and replace all the cam bolts if the bike has a lot of hours. Cheap and can easily be done without pulling the engine.


KTM changed the front axle size so newer wheels won't fit. The rear is the same. 


I consider the RFS 400 to be one of the better bikes KTM ever made for all around use. You'll enjoy it.  :thumbsup:

I just picked up a new to me 2004 version of the same bike. I live at 6400 feet and wanted to make sure I was in the ballpark for jetting so I picked up a JD jet kit. Came with the diaphragm mod and an o ring mod. Throttle response is much better. My first 4t and I an enjoying the even steady power of the 400.

I just picked up a new to me 2004 version of the same bike. I live at 6400 feet and wanted to make sure I was in the ballpark for jetting so I picked up a JD jet kit. Came with the diaphragm mod and an o ring mod. Throttle response is much better. My first 4t and I an enjoying the even steady power of the 400.

Open your forks up and remove the center bushing and the aluminum spacer if it hasn't already. While you're at it replace the fork seals with SKF units.


Many people think the '04 was the best of any of the 400's. Not very many of them were imported either.

I appreciate the advice. I have been researching a thread on KTMtalk that covers that mod. I will be pulling the front forks and reworking as soon as the snow starts falling. I am planning on removing the center bushing and spacer as well as replacing the remaining two bushings with new and the new seals. The forks are really harsh and I don't think they have ever had anything done.

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