How to wake up a 400ex?

[Harper25]

My daughter rides an 07 400EX and she is a good little rider that likes riding my 450R a little too much LOL!

Her 400EX has a full sparks exhaust and a K&N filter/prefilter and it runs OK but what can I do to really wake it up without ruining reliability and such?

I would really prefer to keep it stock bore and stroke but I figured bump the compression up with a piston kit, change cams and port the cylinder head (maybe a new CDI)....can I really wake it up for her with those modifications or will it take more than that?

I am not sure what to expect out of that motor?

We mostly rip around the sand at Little Sahara (Oklahoma) and then some trail riding here and there.

Thanks in advance for any info!!

Jeff Harper

[Steve86trx250R]

The mods you said would help while you're in there I'd upgrade the head studs as well if you're bumping up the compression to prevent blowing head gaskets you could also lose the airbox and put a clamp on k&n filter with an outerwear