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2003 WR450 runs poorly with headlight on

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I recently bought a California street legal 2003 WR450 set up as a supermoto. Pretty nice setup - Excel rims/Talon hubs, Brembo radial master, Braking 320mm rotor, Braking 4 piston caliper, FMF header, suspension redone for supermoto. 

 

The bike had been sitting for close to a year. I checked the valves and they're in spec. I cleaned out the carb, it was pretty dirty. It now runs pretty well when the lights are turned off, but when I turn the lights on I can't do anything more than putt around. If I stay at small throttle openings and low RPMs it runs fine, but if I open the throttle much it falls flat on it's face. I only did a few pulls with the lights off, but it seems to run well that way. The previous owner now admits that it was acting that way before (he didn't tell me before I bought it, oh well). 

 

I'm planning on putting a new battery in the bike - probably a Shorai - but I'd rather not kill it, which I suspect the current charging system will do. 

 

I have a good multimeter, so I can check what I should this weekend, but any suggestions on where to look first would be appreciated. 

 

Thanks for any help.

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I would go through the whole harness and look for a worn wire off the lighting cluster switch that is grounding out.

 

That, or the system is running a high wattage light system, but the stator can't handle it.

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The lighting appears to be stock. 

 

I'm reading elsewhere that a dead battery can cause these symptoms. My battery is pretty dead as far as I can tell. I guess I'll try replacing the battery and seeing how it works. 

 

Is there an inexpensive voltage gauge that people would suggest? I'd like to be able to keep an eye on voltage so I don't trash an expensive lithium battery. I'm thinking of swapping the ignition switch behind the headlight for a Baja Designs keyed switch, and then wire up the voltage gauge so it turns on rather than the LED. 

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I realized that the battery in my SV1000 streetfighter was the same one that Shorai suggests for the WR, so I stole the battery from that bike and rode into work this morning (14mi total, 9 on the freeway - I stuck to lower speeds than usual due to 14/40 gearing on 17s). I turned the headlight off where I reasonably could, but didn't have any trouble on the way in even when the headlight is on. 

 

Of course, I don't know whether that's due to the battery feeding the bike, or whether it just needs the battery to act as a buffer. Either way, it seems to work for now... if it still has enough power to fire the starter when I get home tonight I'll probably continue the testing. 

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Is there an inexpensive voltage gauge that people would suggest? I'd like to be able to keep an eye on voltage so I don't trash an expensive lithium battery. I'm thinking of swapping the ignition switch behind the headlight for a Baja Designs keyed switch, and then wire up the voltage gauge so it turns on rather than the LED. 

 I have one of these mounted on my bike.  $8 shipped on ebay.  I've got the blue one, can't see it in the sun but it does the job. 

volts.JPG

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Turns out it has charging system problems, it started doing it again with a good battery. 

 

It appears the electrical has been converted to DC if it matters. What should I look at first?

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Regulator rectifier, I just had mine go bad too, I had intermittent spark and hard starting.

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Also if the electrical had been tampered with it could be that when the light is on, there could be issues of crossing the A/C and the D/C electrical systems

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I suspect it's been converted to full DC, although you're right that it could have been done wrong. 

 

I was riding home from work at 55mph or so and it started sputtering. That felt very similar to what it was doing before I replaced the battery, so I tried turning the headlight off. At that point it rode fine, and seemed to charge the battery some (meaning I could run the headlight a little more). 

 

I put 2 tanks of gas through it with the new battery, largely with the headlight on even if it didn't need to be. The headlight wasn't on full time, but clearly I can run it for a reasonable amount of time before the battery drains. 

 

The symptoms: with the headlight off it runs great and seems to charge. With the headlight on, there's an rpm ceiling above which it doesn't like to run. 

 

I'll have to take a good look at the R/R this weekend and see what it appears to be. Is there any reason I can't run a sportbike one? I know they're pretty interchangeable among sportbikes but don't know about dirtbikes. 

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A sport bike one would be larger than necessary and you would need to find the pinout. I'll try to remember to take a look at the wiring diagram, in the mean time you check and see if there are extra plug or harnesses in your system. Take pics of your controlled and wiring harnesses and your reg/rect,and we'll see if we can work you through this. Just need to know what I am working with.

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They aren't that large, and they have much larger heatsinks which helps them stay cool which tends to help both efficiency and longevity. 

 

Most sportbike R/Rs use 3 AC lines in, then a hot and a ground out. That's pretty easy. I've swapped them on other bikes before, just not dirtbikes.

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IMG_0342.JPG

 

Can anyone tell me if that's the stock R/R? If it is I'll assume there's very little DC charging and that I can likely solve my problem by retrofitting a different R/R and floating the ground. 

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If I can get a sportbike R/R to work I'm gonna do that, waiting on word from other people... I trust OEM parts a lot more than cheap aftermarket stuff. 

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After doing a little research, I guess I'll buy a Trailtech. From what I'm finding online, I'll need to float the ground on the stator as well. 

 

While I can cut the existing wiring and splice in the generic one if I need to, but is there a plug and play option?

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