Motorcycle Repair: 98 honda 400 quad starting problem, silicon diode, motor windings

Question
My quad won't start unless I attach a battery charger to the battery leads. I swapped the battery for another good one-no dice. The motor turns over but won't start, unless I hook up a charger. I changed the plugs, the starter switch and swapped the coil but no improvement. Also, the engine will only run so long as the starter button is held down. Any ideas?

Answer
Rob, the whole ATV/ATC off-road bike deal is not my area of expertise and I don't have any technical information available to me. I checked to see if there were any online wiring diagrams, but nothing came up in an initial search.

Be aware of a few things that I think are important....
The ignition is CDI, which in most cases is self-generated.
When the motor is turned over the pulser coil is activated by a trigger magnet on the flywheel. This, coupled with voltage generated by the stator into the CDI module creates an ignition system signal to the coil, which creates a spark at the plug. A slow turning starter motor may hamper the ignition system from developing a solid spark for starting/running

The electric starter is a separate circuit, dependent on a fully charged battery, an operational starter solenoid and starter button switch, plus the starter motor and associated wiring. There is a silicon diode in the harness, perhaps for part of the safety switch wiring. If the starter brushes are getting worn or the motor windings are getting old, the starter motor may be in need of replacement, so it can turn the motor over, fully.

http://www.powersportspro.com/partsfish/login.asp has illustrations of parts components. You didn't mention which version of the 400 you have and the 4x4 is different than the EX in many ways. I saw a reference to a 3 way diode on the Foretrax Foreman illustrations, near/in the fuse box. That part may have an effect on the starter and ignition circuit.

Here's another link to an ATV site, that may be of more help. I strongly suggest you get a shop manual with wiring diagram as these things are rather complicated with the various sensors and safety devices incorporated into the design. http://www.atvriders.com/index.html

Bill Silver