05 WR450 - challenges since adding lights

A few weeks back I street legalized my bike - I addded a high/low beem switch, brake light and license plate light - all pretty basic wiring. Since doing this my bike runs fine for 45 minutes and then starts to act like it is running out of gas - it runs very poorly and gets to the point where it will stall and not start. When I charge the battery it fires up fine. ANy thoughts? I have thought about replacin the battery but not sure if this is the problem? When it will not start - I can't even kick it which tells me that it is not the battery because the bike should kick start without the battery attached. Any thoughts would be appreciated - thanks

I'm pretty sure I know as I had the same situation on my '08. It sounds like your stator is not keeping up with the draw. I'm guessing that you have an aftermarket or rewound stator where the ground is floated and all the juice is run to the battery. The bike is actually drawing it's spark from the battery (a Yamaha thing and not necessarily typical) and your lights are drawing down the battery beyond what the stator can keep up with (at that rpm).

I had the same thing happen with my bike on a night ride with a Trailtech stator. One of the side effects was that the bike was an absolute bitch to start cold, but never a problem when warm. I rode for about 30 minutes before the bike started cutting out on me. As soon as I shut off the lights, the bike returns to running normal. In my case, there was never a problem with the stator, but rather the way I wired the regulator/rectifier. Do you have a blue wire on your reg/rec that is going to the negative terminal on your battery? If so, disconnect it. The Trailtech reg/rec has a 5th blue wire that is supposed to take overcharge to very small (less than 2 ah) batteries and run it back to the reg/rec. This wire greatly reduces the charge that is allowed to go to the battery. Once I disconnected mine, my bike went from about 12.58 volts at idle (and never got much more than that even at 1/2 throttle) to about 13.7.....a very big difference. Disconnected, the bike also starts like a champ now.

I'm just making assumptions because you said you just wired up some street legal equipment and maybe your stator has been redone. If that is not the case, you might just need to rewind the stator to make up for the added load. The bottom line is the bike draws it's spark from the battery and when you add too much load, it cannot keep up and you'll actually notice it in the spark probably before even the lighting.

Good luck :worthy:

Great info Brett on Battery providing spark. Did not know that.

Great info Brett on Battery providing spark. Did not know that.

Yeah, it's kind of a weird deal, but I'm not saying it's necessarily a bad thing. Seems like lot of bikes have about two separate poles wound to service just the spark and often times they are of a different gauge wire (usually smaller). I'm sure there are advantages to that, but I like to think that having all the juice from the stator running through the battery to service both lights and spark possibly is a more efficient use of the power and maybe less wasted. Yamahas seem to have pretty strong charging systems in general. Maybe the downfall of this is if your battery is stone dead I guess it could open up problems getting spark to the bike although I have heard people say that they have disconnected the battery and still had no problem running the engine so the wiring could be a bit more complicated than what I'm saying. I'm sure the guys at Baja Designs could give you a much better explanation.

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