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Kx250f electrical problem

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First of all iam from Germany so be aware of grammar mistakes ^^

sadly no one in a german forum could solve my problem. i bought a 2006 kx250f and rebuilt it but because it wasnt running. 

i put in a new piston and cylinder, put in new shims and changed the camchain. i also tested the valves and they seal quiet well so compression is in spec. carburetor was completely rebuilt (jetted as it says in service manual)   accelerator pump is adjusted. also the bike had no cdi box so i bought one of a 2005 kxf250

now my problem: the bike dies when i rev it. it revs to about 1/4 throttle


i tried almost everything, new stator, wiring harness, sparkplug, ignition coil, crankshaft position sensor even the cdi box

all ohm readings are in spec, i tested them with a multimeter 

 here is the thing: i thougt it was the cdi box because it is from an older model but with a newer one from 2006 and one off a 2008 model it wont even start(no spark)


i hope someone has suggestions on what is wrong with my bike 

thanks in advance philipp :)

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Hi Philipp!

Very high probability that you have a slipped camshaft sprocket. This causes all various kinds of troubles that look alot like electrical and timing problems. So my first advice is to check the cams for the sprocket to be out of time (slipped on the shaft) relative the cam lobes.

Another you did not mention is the throttle position sensor. It may not be adjusted or may be faulty.

Another which happens, but is often overlooked, is a failing kill switch button. Sometimes corroded wiring or kill button internals can act up on vibration causing weird problems.


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