Need electrical help on a 2003 WR450.

1 reply to this topic
  • StreetbikePimp

Posted February 25, 2009 - 10:34 AM


Hello All,
I own a 2003 WR450 that I have “YZed” for racing Harescrambles. The issue that I have and the issue that I’m trying to find an answer to is…”Why do I keep frying ignition coils?” What I mean by fried is the bike will stall if the RPMs drop below 2800, and I know it’s the ignition coil because as soon as I replace it with a new coil, I can dial my rpms to as low as 1500, and the bike will “putt-putt” like a tractor all day long. (in neutral of course) I am currently on my 4th ignition coil is 6 years.

Here’s the back story: I chose a WR to race instead of a YZ because I wanted the softer suspension, the 5-speed tranny, and the ELECTRIC START. As time went on, I became frustrated with the electric start because it was unreliable. I don’t know if it was because I rarely saw 3rd gear during a race, or I stalled too much, or some other reason, but 9 times out of 10 it was faster to kick start the bike, then it was to hold the button and listen to the motor crank, and crank, and crank (with your fingers crossed) and wait for the bike to start as people pass you. Eventually I gave up and just reverted to kicking it all the time.

Since I was committed to kick-starting the bike, I removed the battery and the starter, to save weight. I have also removed the headlight and taillight as well, and per ncmountainman’s posts, the negative cable is grounded to the regulator/rectifier. The other modification that you should be aware of is that I have an EZ-start Rekluse clutch without the clutch perch adjuster. So this means there isn’t a clutch handle for me to pull in if I think the bike is going to stall.
So this is where my problem stems from. With the EZ-start clutch, it is important that your idle is set between 1800 and 2000 rpms. If it’s any higher than that, your bike will try to move while it is in first gear, or stall if it’s under load. So then, when my coil goes “bad”, the bike stalls every time the rpms drop to idle speed. Granted, I could turn my idle up, and ride the brake, but at 2800 rpms, my bike is in constant motion, and becomes hard to control.

So this is my question: It seems like if I put the battery back in, this will solve my problem, but I really, really don’t want to. It is 6 pounds of weight sitting high up on the bike, and YES, you can feel the difference when you race a harescramble, and you’re flicking the bike from side-to-side about 300+ times during that race. Furthermore, forum research suggests that the bike should be able to run just fine without the battery. So, am I missing something? I’m not an electrician, so I need some expert advice. Will I keep frying coils if I don’t put the battery back it? Is there something else cause the coils to go bad? No headlight perhaps?

I’ve wrestled with this problem for about 3 years now, and since I don’t have the funds to go by a YZ right now, any help you guys can give me would be appreciated.

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  • DuneDevil

Posted February 25, 2009 - 03:05 PM


Maybe put a large (1F?) capacitor in place of the battery. As far as the rest of the bike's electrical system would know, it would think there was a battery there.

As far as killing coils though... I don't know. If your DC voltage is getting higher than about 14V while the bike is running that could be damaging the coil...


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