Yamaha wr450 2008 spark issue

Guys I need help. I have a alloy framed 2008 wr450 with no spark.

The bike was running fine all day in December when I then power washed it and put it away. Two weeks later I got it back out and it had no spark. I have checked everything electrical and found that the pick up coil maybe at fault. This was replaced with a genuine and brand new pick up and ac magneto unit but still no spark. Again every electric part was checked and I found no faults so I changed the CDI box for a brand new genuine part but still no spark. For a third time I checked every electronic part and found no faults so I changed the wiring loom for a second hand but guarenteed genuine part with still no spark. However if I put a wire between the white wire from the ac magneto and the white wire from the pick up coil it sparks and starts. Does anyone know what the fault can be as I'm really finding it difficult to fix and it's an expensive orniment :-).

I've just had a thought, if I'm bridging these two wires and getting a spark and the engine runs but very poorly I'm surly feeding the motor still with AC current and missing out the regulator/rectifier. So if this unit is for some reason grounding all the AC current and not converting it to DC for example am I right in thinking I could have a regulator/rectifier problem?

Scrap that I've tried the regulator/rectifier on a slightly older WR and it's working fine as is the ignition push button switch. I'm really struggling now :-(


How did you figure out to bridge the 2 white wires?  If my bike was having the problem that yours is, I would try these.

Check that the black wire coming from the regulator is actually grounding.  Use a multimeter, you have one, right?

Disconnect the power switch and connect the red and brown together.  The black and the red/black go to the indicator LED, so those don't need to be connected to anything.  

Disconnect the headlight and see if that makes a difference.  

Pull the kill switch off the handlebars.  

Check the fuse, under the seat.  It's got 2 in there, one is just a spare.  

Is the battery charged?  Your multimeter again, it should read about 12.6 fully charged.  

Pressure washers are great and I use one but they can force water in where it doesn't belong.  

Do you have a wiring diagram?  If not, I can post one.  

Hi there, yes I have a wiring diagram and I have tried all that u have mentioned. I just decided that there must be power somewhere so looped the two power wires together. I am thinking that maybe, just maybe some how the flywheel has lost it's magnetism and the pick up has nothing to pick up. Maybe the power washing was just coincidental, long shot I know. To be honest as you can tell I'm clutching at straws now with it :-(

Check the pick up for metal debris stuck to it's tip, canceling out the trigger

Yep done that, it's a brand new Yamaha part but done that just incase, still no spark :-(

Anyone got a flywheel for sale or know where I can get a good flywheel from. As I'm going to have to change it as it's the only bit I haven't changed and the fault is still there

Guys I've taken the flywheel off and well it's got varying degrees of dents in it. Question is should it have, could something have broken ie magnets inside that I cannot see to prevent the bike sparking. Here's a picture

ImageUploadedByThumper Talk1427389939.611262.jpg

Not normal but unlikely to have damaged the magnets


If your bike was running ok, then you jet washed it and put it away and now it doesn't start it ain't your rotor


As said before, its gonna be an electrical connection somewhere


As a matter of interest, where about's in the UK are you?


A few questions

Tried a new plug?

Have you got voltage at the plug cap connector when you turn the engine over?

Have you voltage at the CDI output when you turn the engine over

Have you voltage at CDI input when you turn the engine over

Have you voltage out of the stator?

Have you got voltage out of the trigger coil?

Edited by GuyGraham

Hi there I'm in the northeast of England. Not sure on what readings I'm supposed to be getting at what wires in and out of the CDI. Plug and coil pack is good as tried on another bike, but there is nothing at the loom end (obviously). I've done the ohms test on the pick up which is within normal parameters but as for voltage tests if it's not in the book I'm struggling as my electrical knowledge is poor to be fair. I've changed all the switches onto another slightly older bike and that bike still works so these must be ok. Got to be something I haven't changed, which leaves rotor and reg/rec unit. I disconnected the reg/rec on the other bike and it still starts so I'm guessing it's not that. I'm with you though I didn't think it would be particularly common for the rotor magnets to fail and they are £200. Can u tell me what volts I should be getting at what wire and I will give it another check over :-)

North East is a bit too far form me in West Mids to be of any practical help


Absolute readings aren't really important, as regards out of stator, trigger, cdi etc, it just comfirms the ignition is working up to this component

Stick multimeter probes into the Red and White wires from trigger coil. Kick bike over and see if you get AC voltage out of it - if not its dead

Do same for White & Yellow from Stator

Check at CDI input - white (which goes into White/Red wire on CDI side of connector) & Red

Check Orange to ground for CDI output

Check Orange to black at plug cap connector



Start at plug cap connector and work backwards and find where there is no voltage

Use the kickstart because this discounts any of the starter circuit relays/diodes


If no voltage out of CDI then it could be CDI or one of the realy/diodes etc including also the neutral switch


Also check the grounds into the CDI (using multi meter resistance scale) which would stop it starting - should be open circuit - if there is a circuit you have a short


Black /White (engine stop switch) - to ground - should be contintuity in run position

Check you have 12V into the CDI - Brown wire to ground should be 12V DC

Check Red / Black with has continuity to ground with main ignition push button is on

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