I've had my White Bros CDI box for about a year now. Just went to go for a ride and the bike wouldnt start. After a little trouble shooting, I put the stock CDI box back in and what do you know... started right up. Anyone else run into faulty WB CDI box..?

 

I had my CDI box modified for my 300EX. After several successful rides, my ATV started blowing fuses. I put another stock CDI that I purchased on for my last ride, and now, no blown fuses.

I've questioned the placed that modified it and even Curtis Sparks Racing, and neither think it has anything to do with it.

Heavy J

 

Friend had same problem. Thought it was having ign troubles. Wouldn't start and wouldn't start. Put a new plug in, band aid fix for a while. Kept feeding it spark plugs, until finally it gave up...You're not alone from what I have heard....I have heard of several failing now...

 

There's a known problem with using aftermarket CDI's on the 400EX, regardless if it's a WB or XR250 CDI. Apparently, when it's cooler or cold outside the starter can't turn the motor over fast enough to allow the CDI to send the signal to the coil telling it to fire. If it starts with the stock CDI, and then the WB or XR250 CDI works after the motor is warmed up, that's what's causing the problem. If not, it's probably bad. I remember a while ago WB had a problem with some faulty CDI's, but I think most problems were related to the cold start issue...