04 wr450 start issue

I have an 04 wr450 with a fresh engine, 13.5 je piston, yz cams and timing, factory r&d pump cover and fuel screw, vortex x10, rs3 full system and was dyno tuned after rebuild (59hp).

When the bike is cold, like after sitting overnite it will start straight away, just pull the choke and hit the button. Once it warms up it will still crank fine but kinda just burbles like timing is out and will not fire, but will start instantly off the kicker. Sometimes it fires off the e-start after 4-5 secs when hot but not very often.

I have checked the valve clearances and they are spot on, voltage to the cdi while cranking doesnt drop excessively, battery load tests ok and carb is jetted properly for my area.

Is this because of the yz cam/timing or another issue all together?


Just to cover all of the bases... are you pulling the hot start when the engine is warm? I MUST pull the hot start when my engine is warmed up for it to start easily. (05' WR450)

...As far as it starting on the first kick while the starter just whizzes away:

There is a built-in starter switch detector in the CDI that causes the engine to not fire on the first few revolutions when using the e-start. There is some discussion about the reason that the engineers added a few dead revolutions when using the starter. One theory is to reduce the chance of kickback potentially causing undue stress on the starter mechanism, so modify at your own risk.

This mod requires that you find the blue/white wire that exits the CDI disconnect and isolate at the connector under the tank.

Just to clarify:

There are two blue/white wires that are associated with the CDI wiring harness, one that comes straight from the CDI and enters the connector next to the gray wire (that most of us have disconnected). There is another wire that exits the CDI as sky blue and changes to blue/white at another connector (at least on the 05' US version) leave this wire alone.

I have done this mod and rode a few times since and so far it works great.

Thanks to Thumper_Bloke for this tip...


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