09 KXF 450 problems... Missing at high RPM

I have a 09 KX450 that my son rides in a open A and a sport A offroad classes. It started missing at high rpm after it gets hot. I have had the head rebuilt with K/W valves and a new top end. Still missing. We have also changed the fuel pump, stator, coil & condenser, spark plug & cap. I have pulled every wire connection loose and sprayed with a cleaner. The only thing we haven't changed is the voltage regulator. I've always understood the voltage regulator either works or it doesn't. I'm starting to think thats not true. I've already spent a ton trying to find the problem. Have you any suggestion. I am at a lost...

Thanks Curtis

Ign coil? If its only when hot.

Cracked plug would also.

Or is just hitting rev limiter. Lol

No it's not the rev. limiter...

I've changed the coil and 3 plugs with a plug cap...

Recheck valve clearance. May be floating a valve.

Have you checked to see if the TPS is in spec?

I'm not sure what TPS is... I was hopping Ron would jump in and give me a clue as to whats wrong. I'm now thing the wiring harness could have a broken wire some place....

Had this problem on my '10 and ended up having to remap it and havnt had an issue since

Any new ideas.......

The only thing we haven't changed is the voltage regulator. I've always understood the voltage regulator either works or it doesn't.

you could meassure the voltage (approx 14.2V at capacitor, 5V at TPS) ,slowly go up with rpm and see what it does...

as stated, check the TPS. its a variable resistor and when you apply 5V to blue (black ground),

then the output (yellow) should have about 0.65V at idle and a continuous increase to approx 3.9V at WOT

did you check for FI error codes?

Edited by kawamaha

FIX'ed!!!! and I now know what a TPS is..... Started with a loaner bike. Changed the cid box with no change. Put the throttle body from the loaner on my bike and it ran like it should. I put the TPS from my bike back on and it was back to missing.... found the problem... put my throttle body back no with a differant TPS and it running again....Thanks for the help....

you know you have to adjust the TPS? if you just put it on and its running fine, you have had good luck...

nevertheless, good to hear you found the problem :thumbsup:

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