2004 Yam Bruin 4X4, Motor won't turn over with out adding power to the Blue/white wire coming from the CDI into the starter relay. 1. Should there be constant power on this wire coming from the CDI. 2. Are there any internal relays inside the CDI that would need a signal from an external switch/sensor to activate power to this blue/white wire. Attached is a wiring diagram to follow along.

 

No, the CDI does not have relays inside of it....but it is looking for other switches to be "made" in order to close circuits to turn over the starter.....left handlebar switch made ( if in gear ), neutral switch to be made, ignition switch on...Starter push button when depressed. The CDI is not the issue...something else is.

 

I followed the circuit on the diagram. (#5) fuse on starter relay supplies power to main switch (#3) switch on passes power on thr to fuse (#23) power than goes to left handle bar engine stop switch. switch on than passes power onto oil temp warning light (#17). (#29) start switch than put ground on #17 oil temp warning light and #6 starter relay. (#19) diode checks to be good. neutral sensor light on. and I still don't get power on blue/white wire out of CDI...... Maybe bad CDI?

 

I certainly admire your troubleshooting skills, and attention to details in regards to the diagram but, in my years of working on/repairing dirt bikes and ATV's, I have yet to see a CDI fail in which it would not still allow the starter to function and turn an engine over....it was always a "no spark" or intermitant spark issue. Here I would recommend checking the wiring for damage/breakage and if you find the wiring/connectors are good ( ohm out ) then yes, change the CDI. And for sure post your findings/results here so we may all learn from this.

 

Just checked wires for any breaks or damage, I replaced 5 wires that seemed to have some questionable performance. But still no start! So I used a jumper wire on the starter relay red wire (power from battery) to blue/white wire coming from CDI I am able to crank engine and notice no spark also!.. I am going to assume that the circuit that triggers power to the blue/white from the CDI is dead or has no signal to activate it. So..... I order a new CDI on Ebay $45... will post results! Where can I find a circuit diagram for the CDI Part# 5UH-85540-00-00 (F-8T40371)

 

It's starting to sound like a CDI problem ( the no spark ), and hopefully it is. There aren't many tests for CDI's, one must prove everything else is good, then go with a new CDI. I doubt you will be able to find a diagram for the CDI. Was the left handle bar switches good...the kill switch and the start in gear switch?

 

That blue/white will only be fed power when the bike is in neutral or park, so you can't start it in gear. There seem to be diodes in the neutral switch circuit, I would suspect these, if the neutral light is working. It may be the CDI though, why do they make the ignition circuit so complex?

 

Also you would think the service manual would have a section on troubleshooting the CDI circuit. I bypassed both neutral and reverse switches to see if the CDI would feed power to the blue/white wire. But no good. Waiting on new CDI to arrive... keeping my fingers crossed hoping that is it.

 

Well my ATV Connection friends turns out it's a bad CDI! I now have a nice strong blue spark and the engine cranks over no problem. Paid $45 on ebay for new CDI. thank you all for your help.

 

That's awesome! Thanks for letting us know what the fix was and...speaking for me, I just learned something new! Thanks