'03 WR450F. Low voltage to TPS. CDI?

Okay I have had simular problems on the same bike but after toggling the light switch a few times, restarting the engine and setting the light switch on the opposite position it seemed to fix itself... i know how dumb this sounds but i believe the reason it did this was because the owner before me had a hd light on it and messed with the electrical a bit.... maybe test output with and without the light on... just my experience with a simular problem...

Check the cam timing, confirm both the marks line up and the lobes look right (cams have been known to move in the sprockets unless welded).

I still haven't managed to get this bike running right.

Today I checked the cam timing as William suggested, it was fine. I also took the opportunity to check the valve clearances while I had the head cover off. They were all spot on, at the the tight end of range.

Also I've taken every electrical connector apart and cleaned it up with a small dental brush and WD40.

Any other ideas what to do next?

At this point, I'd have to say the stator is suspect.

Oh well I guess I'm gonna have to start throwing money at it and just keep going until I find the problem.

I think I'll go for a upgraded stator/DC conversion kit first (£133 or $210 - ouch) first

and if that doesn't fix it I'll take the head off and check out the valves, piston etc.

Just a thought, does the auto-decompressor ever cause problems on the WR450?

When the engine is struggling to rev it maybe sounds like it could be a valve not closing properly.

I've got the bike back together after stripping the head and checking the valves. I've also fitt6ed a new coil/plug cap and choke plunger (the old one was a bit bent).

It's still not running right and won't rev past 5000rpm.

So I'm going to take William's advice and change the stator and crank position sensor next. The Trail Tech one, this one, is a similar price to the OE Yamaha item and is apparently higher output and a DC conversion.

Anyone think the TrailTech one would be bad choice for any reason?


The Tsil Tech one will be fine. Is your bike alread coverted to all DC? Do you already have the larger rectifier/regulator?

Well I've fitted the TrailTech stator/CPS/Reg-Rec but it still won't rev properly.

This getting me down now.



I seem to have a same kind of problem (at 6000 rpm) - see http://www.thumpertalk.com/topic/1107921-sudden-drop-in-acceleration-power-at-full-throttle-and-high-rpm/


- Engine was running bad at low rpm

- Noticed wrong valve cam timing setting - I noticed this when I was checking valve play (minimal adjustment was needed)

- Changed cams timing to spec + replaced ignition coil + replaced oil filter

- Engine running now fine at low rpm, but not at high rpm --- :goofy:

- delayed the outlet cam - 1 teeth- to get better cleaning of the exhaust gas (valve opening overlap inlet - outlet), did not work...put cam outlet back to normal...

- Tried with and without DB killer (exhaust opening - restriction more / less) - No effect

- Now I suspect the ignition coil + oil filter

- Gonne run without oil filter today and check resistance levels ign coil vs spec.


PS did you solve the problem finally? Or sold bike :rolleyes:




Edited by Arjan van Druten

I would remove the carburetor and clean it inside out.  It probably takes you one evening to do so and then you know its clean and isnt causing you this problem.  

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now