Not sure of the year of the bike but i believe its a 2000-2008 Yamaha Kodiak 400 4x4. I recently got this bike to fix up and it runs smooth and good but i just replaced the battery, old one was a goner and ive found that the battery inst charging. I can start the bike up and ride for hours but if i turn it off and go to start it the battery is very weak or dead. The fact that itll ride for hours with a dead battery makes me believe that the stator isnt bad. Before starting the bike it reads around 13 volts when started and revved up the voltage doesnt change itll just start dropping eventually if you keep starting it. Am i missing a terminal on the battery all there is on the positive side is the red wire going to the starter solenoid and the solenoid just goes to the start i dont see any wire that connects to the charging system. Im thinking its the Rectifier or im missing a terminal because i dont see how itll charge if its only hooked to starter solenoid and starter.

 

If I've got the right model,regulator shows to be behind the rear fender area, item #17.Yamaha ATV Parts 2002 KODIAK 4WD - YFM400FAP ELECTRICAL 1 Diagram If you can trace the yellows(normally?) from the stator to the regulator,there should be some small resistance between each one with no yellow shorting to ground. This should eliminate the stator as the main problem.You can get an oem or take a chance on a cheap 15 buck regulator.Voltage Regulator Rectifier Fit Yamaha YFM400 Kodiak 4WD 2000-2006 2001 02 03 04 | eBay

 

Ill go outside and try to do that in a minute here but if i remember correctly there were 5 or 6 wires going to the regulator a red, a black and the other 3 all looked white some with stripes i think not the usual yellow. May be stupid question but how does the battery get charged if the only terminal on positive is the terminal that feeds to the starter solenoid and the other side of the solenoid goes directly to the starter motor.

 

Then I would guess the white wires with the stripes is the wires from the stator to the regulator?? This is where the manual comes in handy... Again you can test resistance between each wire. Should be some resistance with no wire shorting to ground. That is just have the red probe on the meter on the wire,the black probe to a good ground. See if this video helps along with this article. Technical Article: How a Motorcycle Charging System Works - ElectroSport IF the stator isn't suspect then get a new regulator/rectifier.

 

Most Yamahas and Suzukis have a fuse on the solenoid, and one (or two) of those thin wires that go to the multi-pin plug on the solenoid, are the live feed wires from that fuse to the ignition switch. The fuse gets it's power from the binding post connected to the battery. That is why you have to connect the thick wires to the solenoid the right way round.

This will not have anything to do with your problem, unless you are getting a high resistance here, as the wire from fuse also goes to the regulator.