i got a catalog from nik's pro x and they show a .020 and .040 over

 

Sireland

Once I took out the right pilot jet and closed the airbox back up it ran much better....It still has a flat spot if you pin it off the line, but it starts and runs on the top end much better....

I will let him work with this for a while and will eventually go to CT Racing for their power package

Thanks for the help

 

BTW, the FX55 is still available in other brand names. See the current post "1st ATV". It's on Ebay for 620, free shipping.

 

The FX-55 was impressive...the KMX-50 was not

I hear that there is an FX-75 now available this month on the same frame, but more cc...but 1 speed tranny


Thanks for the post...I will look at the post

 

would like to thank everyone for the great ideas and input into getting this little pig to move! fist of all i think the kfx50 is a great quad for begginers who are young and small, my son started solo riding at 3 he is now 4 and weighs 38lbs. Mine is the 2003 model kfx but im pretty shure all the 2strokes are the same. so here is what i did

1 inch wheel spacers in the rear only , he had a bad habit of rolling it over
removed the rear shock and replaced the spring in it with one that had a 65lb spring rate 35$. it was music wire with a .187 spring thickness. this made a world of difference, the stock spring is set up for a 380lb man!

removed intake restictor and jbweld the transition smooth, while i was in there i cleaned up the casting and opened it up, matched the intake to the head.
removed the piggy back pilot jet and replaced the one left in it with a17, bumped the main up to a 65. also drilled the airbox
pulled the head and did a slight port job, mostly clean up casting and match ports. polish the exhaust side
milled .035 off the head and put a new wiseco piston in
went with the fmf turbine2 exhaust because of price 175$ and i am not dissapointed
removed the oil injection and went with premix
This thing really rips now, of course it wont increase your top speed but it has some *****! kid has no problems starting from a dead stop on steep hills wich was a major drawback of this bike, plus it will actually burn out wich he is into