3nc cdi 3 wire servo help please

  • morning all. firstly this is my first post. great forum really helped me getting the old bike running nice. the bike was gifted to me a few years ago by a friend but sadly he,s passed away since. i was hoping for some help regarding a 3 wire servo, i have the 3nc00 type cdi on my mid 90s dtr. the bike is used as a field bike these days as the thieves caused to much damage to put her back on the road. my main question is what do the 2 wires on the connection block do? where could i wire them to so the power valve works. there's no battery and no female connector for the servo. i have the black and yellow bullet wired but do i need to earth the connection block or give it a constant live or both? if so could the live connect to the ignition coil or the magneto wires? ive serched the forum for 3 days before posting but cannot find what im looking for. so basicly im just hoping someone could please let me know what i should do with the black and the brown wires in the block to get the servo working?

  • Firstly you're going to want the check the rating of that stator on those old engines.

    They struggle to power the lights, let alone operate the servo, I have a strong suspicion that those wires were a dedicated live and negative for the servo to operate. I doubt the servo will be supplied enough power otherwise.

    Don't quote me on that. I'd have to dig through my Haynes manual to know for sure.

    I'll be sure to upload the wiring diagrams to this site to make easier for others in the future.

    I would recommend getting a battery fitted, the servos tend to be a bit hit and miss without them. I know my DTRE would play up if the fuse went between the battery.

  • Hi callum. Thanks for a swift reply. From what I've read up on once the engine is running it should power the servo ok it just won't do the cycle when ignition is turned on. But I'm not experienced with electric side of things. It's a 3bn03 bottom end with the 3 stators. I did read a post a week or so ago where someone had the same question as me but I can not find it for love nor money now (typical lol). If I remember rightly he said something like one is a constant earth and other but I'm not sure if I'm remembering right or not but the other could be a switch earth from the ignition but as said I can't remember.

  • Also I have a Haynes but I can't seem to find a wiring diagram in there that relates to the 3 wire servo. I have the 88 to 97 manual.

  • @watty I'll check my manual, like I said, DTR's struggle to power the lights, so I doubt it'll power the servo.

    Hence why motocross bikes utilise either pneumatic or gearbox operated powervalves.

  • Thank you very much callum. Any help would be greatly appreciated. I can ride the bike as is without the servo but on the enduro track its all or nothing getting through slow sections which can be difficult without the bottom end power. Thanks again mate

  • @calum yeah if I leave the ignition on by accident over night my servo will take a little while usually the time it takes to warm up to become operational

  • @calum I've got it going. If I connect it to a battery it does its "cleaning" cycle and when I started it and give some revs it works ie moves the pv back and forth.
    My next question is how would I go about charging the battery from the magneto/stator? To keep charge in the battery.

Log in to reply