JD Jetting kit = jetting perfection

[04TRX400EX]

I picked up a JD Jetting kit for the 450/505 SX and installed it over the weekend. All I can say is WOW I have never ridden a quad with such instantaneous throttle response. I only got to ride it around my house but could tell immediately the difference the kit made. I'll be at the motocross track this weekend for sure.

Due to emissions regulations for importing "vehicles" from Europe to the U.S., KTM has to jet their quads (and bikes) very lean from the factory. What happens then is to compensate for an overly lean low-throttle condition, they increase the duration of the accelerator pump squirt, therefore causing too much fuel when you snap the throttle open, resulting in an irritating and very significant bog. Fixing the problem requires a few modifications to be made:

* custom taper needle jet and clip position to richen mixture down low
* larger main jet (depending on elevation) to richen mixture in higher revs
* o-ring or wire mod to throttle/carb linkage connection to reduce throttle response delay
* longer accelerator pump diaphragm post to shorten squirt duration and prevent "lean-bog"
* adjusting air/fuel screw to even out mixture

Just wanted to give everyone a little review. I cannot say how much of an improvement these changes made.

[Quadevil]

It's a MUST DO! for everyone that buys a KTM XC/SX
It even can lead to problems in the engine if the motor runs lean too much time...

[OutlawBill]

Current Mods: This thing needs nothing
just a JD jet kit.

[bbrad mulvey]

whats the part numbers?

[04TRX400EX]

Part number for the kit is JDK017. Here is a link to their website JD Jetting - they have a kit available for almost every bike and quad.

[bbrad mulvey]

nice thank you!

[LT-R450 131]

does it come with a idle screw?? the one with the numbers

[04TRX400EX]

Originally posted by LT-R450 131
does it come with a idle screw?? the one with the numbers

Nope, the idle screw remains the same, as does the air/fuel mixture screw. I haven't touched the air/fuel since I set it per the kit instructions and the idle screw is easily accessible just like on most quads.

[moogie]

I have just got one of these, so i think that JD kit is a must as it was a bit slow on throttle
Also what about slipon...have to do something about that as std even with arrester removed sounds awful

Any suggestions, I see HMF and FMF do something

[04TRX400EX]

HMF and FMF both offer exhausts for the XC version, which will also fit the SX quads. So far, your best bet is Dasa, which seems to be the story whichever quad you have. Dasa seems to somehow squeeze the most performance (not to mention a great sound) out of their exhausts and thus creates the most usable power - just where you need it. I'll be adding one down the road.