cdi problems... motor biker in distress..

Discussion in 'Electrical' started by Tacklebox, Dec 31, 2011.

  1. Tacklebox

    Tacklebox New Member

    Can I use a 66cc CDI instead of the stock CDI that came with my 49cc chinese motor? I found one online that seems to have the upgraded rubber wire that will fit the new NGK plug I bought... My plug wire does not unscrew from the CDI and has no screws on it, completely sealed off and leaving me stuck pedaling.. the upgraded CDI is only 10 bucks, which the new plug wire will cost me almost that... and if I can't use the 66cc CDI where can I find a BETTER CDI than this all plastic POS... thanks for any input
     

  2. Al.Fisherman

    Al.Fisherman Active Member

    All these Chinese HT's 49cc and 66cc use the SAME CDI, among other parts. Haven't heard of a BETTER stock replacement.
     
  3. Tacklebox

    Tacklebox New Member

    thanks

    ok... the CDI i saw was the same just with an upgraded plug wire and boot... it will fit directly on the NGK without modifications, and its a rubber wire instead of plastic... Thanks I will try that route...
     
  4. motorpsycho

    motorpsycho Active Member

    you can put your own wire (they're made of silicone not rubber) on your original cdi. Just unscrew the stock wire and screw a new automotive wire with a rubber boot into the cdi.
    you will need to put the little screw on cap back on top of the spark plug for an automotive boot / connector to snap onto the plug.
     
  5. goggy

    goggy New Member

    Hello. I too think the stock CDI is killing my engine ther must be some up grades out there , and my plug wire will not unscrew! I have changed to NGK plug and cap, but still bike miss fires and will not rev out what should i try next????
     
  6. motorpsycho

    motorpsycho Active Member

    you should be able to just unscrew the wire....just twist it out of the cdi.
    a single cylinder 2 stroke can't mis-fire. it will either run or not run.
    if the cdi is bad, it will either work or won't work.
    it's possible that you are experiencing 4 stroking.
    4 stroking is when the engine is getting too much fuel and not enough air, which will make it run really rough, have low power and the rpms won't go as high as they should.
     
  7. goggy

    goggy New Member

    Ok motorpsycho, I'm sure that i'm suffering from '4stroking' where to start to cure it? I have tried 3 carbs now: the orginal nt , a 16mm mukuni and now 12mm flat slide from a 39cc minimoto! both of these are smoother than the NT but still suffer 4stroking at cruising speed or WOT? bike starts great cold or hot I have also port matched inlet and exhaust so no miss match, answers please thankyou for your time.
     
  8. motorpsycho

    motorpsycho Active Member

    to cure 4 stroking, it requires changing to a leaner main jet.
    this is done by trial and error because no 2 engines will run the same on the same jet.
     
  9. marksie

    marksie New Member

    To jet carb, correct way is to start from main jet & work down requires full throttle run this is main jet only if still 4 stroking, it requires changing to a leaner main jet.once this is right use the needle to correct running from 1/4 to full throttle this is done by trial and error lower needle is leaner lift needle is richer ,other things effect the running like carb slide ,filter type & pilot jet for below 1/4 throttle.
    cheers marksie
     
  10. Big Red

    Big Red Active Member

    CDI's

    Not to change the subject now that you're on to 4-stroking. BUT, I have seen the plug wire GLUED into the CDI. Don't know why they would do this, But I've had to dig out a couple of plug wires from the unit.
    Shiney Side Up,
    Big Red.
     
  11. goggy

    goggy New Member

    Ok thanks guys will have a look at jets and see what can be done , also will dig sparkplug wire out and replace mine is glued on tight! hope i don't damage cdi, but got to be done .
    Thanks for your help :)
     
  12. motorpsycho

    motorpsycho Active Member

    I have never seen a spark plug wire glued into a cdi box EVER.
    who made your engine kit?
     
  13. Big Red

    Big Red Active Member

    Cdi

    Can't remember where I got it. I'm sure it was the cheapest POS chinese carp I could find. BUT, like I said, In almost six years and only God knows how many engine kits (60? 80?) I've only seen it twice.
    Shiney Side Up,
    Big Red.
     
  14. jaguar

    jaguar Well-Known Member

  15. Al.Fisherman

    Al.Fisherman Active Member

    Well here is one....
    [​IMG]

    So now you can say you have. New CDI that I just removed from a sealed baggie.

    But the glue is a non issue as you can cut the wire off and dig the remaining wire from the CDI holder.
     
    Last edited: Jan 5, 2012
  16. goggy

    goggy New Member

    Cool that is just like the one 'CDI' on my bike Al. i shall dig it!
    just been reading on forum about '4 stroking' and taking in what you have all wrote taken carb off again , now I've taken more notice, looking down the inlet port, I turned crank to tdc shock!! theres alot of piston still showing! covering about 30%+ of the port!
    Could i be suffering too rich mix' as this piston will not let the engine breathe fully? If only say 70% of air can get in and i have carb WOT sending 100% lots of fuel in 'richmix" that it can't burn?
    Do you guys think this is most likely to be causing my trouble? and I should 'trim' file my piston first before any other adjustment ?
    Thankyou for your help :)
     
  17. Big Red

    Big Red Active Member

    Glue?

    Thanks for the back up on this one Al. I knew I wasn't going crazy.
    Shiney Side Up.
    Big Red.
     
  18. jaguar

    jaguar Well-Known Member

    No. Raising the piston skirt 1.2mm will give it a bit more top end speed but does not change the needed air/fuel ratio.
     
  19. goggy

    goggy New Member

    Ok Jaguar thanks, i shall reduce the main jet size your link is great! i've read it more than once. My down pipe is now 6" longer and I have modded my stock muffler as in your diag'm, if i end up raising piston skirt 1.2mm i will also chamfer crown on transfer port areas 0.8 at 40deg. Yes i would like your cdi but can't afford it yet,
    Thanks
     
  20. HeadSmess

    HeadSmess Well-Known Member

    ah, the old "file the piston trick"

    overdo it and you lose your bottom end.

    get it right it makes a big difference.

    :)
     
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