03 WR450 from the grave (consolidated)

Ok so got an 03 non running dirt cheap.

New plug (Have spark)

Rebuilt the carb to include all seals and all new jets

New gas

AP and diaphragm look good

Valve clearances still w/in spec

Leak down test on cold motor was 13% all past the rings so probably less if warmed up, had no discernible air at all from intake/exhaust or in the radiators


Still wont start...what am I missing?



when you had the valve cover off, did you check the timing?

is fuel actually filling the float bowl? is your float level correct?


are you kicking or E-starting? kick will spin the motor faster.

I did check the timing. It was off and I corrected it.

Fuel is filling the bowl. Checked height, seat and float are spotless.

Kick starting.

Give it a spray of starting fluid. If the cam and ignition timing is right it will light. Then you know if it's fuel related.

OK so I took the carb from a great running 04 WR450 and still no start.

That just leaves spark problems.

Where should I start?

Just tried the starter fluid. Got a nice loud bang and then nothing.

Was hoping to try a swap out with the 04 known working CDI to the 03 but they seem to have different part numbers when ordering online.

OK so put the non running bikes carb on my running 04 WR450 and it fired right up.

So how to chase spark gremlins?

Have you verified spark?

Have you done a stator check per the service manual?

According to the troubleshooting tree for the ignition:


1. Check fuse -> no good, replace and inspect harness

2. Check battery -> no good, recharge or replace

3. Spark gap test -> no good, clean or replace
4. Check entire ignition system (refer lower instructions)
5. Check Engine Stop button -> no good, replace
6. Check Main Switch -> no good, replace

7. Check Ignition Coil (both primary and secondary) -> any no good, replace
8. Check AC Magneto pickup coil -> no good, replace
9. Check Neutral Switch -> no good, repair or replace
10. Replace CDI


checking harness:

Take a look at the engine ground to battery which is right near the carb.  You may have a loose or dirty connection which will cause all sorts of electrical issues.  


If that's good then look at the whole wiring harness VERY closely.. look for any signs of damage, melting or anything going wrong.  


After that if everything was good, unplug all the connectors one by one and look at the pins for any signs of damage or corrosion..


Still can't find anything.. then start unwrapping sections of the harness to get a close look at the wires underneath all the zip ties.  You'll need about 2-3 rolls of electrical tape to wrap it up again.  (My bike had a open on the neutral sw grounding to the frame which caused a bunch of issues)

STILL can't find anything.. borrow your buddies CDI.



Remember to have fun while doing this.  This is why buying mechanics specials can be frustrating.

Edited by zibbit u2

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