jnmotors racing coil

Discussion in 'Electrical' started by mountainman_oef, Apr 12, 2014.

  1. mountainman_oef

    mountainman_oef New Member


  2. butre

    butre Well-Known Member

    you should have done some more research before buying. those are for aftermarket CDIs with no built-in coil. get a Jaguar or something if you want to use that.
     
  3. Fabian

    Fabian Well-Known Member

  4. jaguar

    jaguar Well-Known Member

  5. mountainman_oef

    mountainman_oef New Member

    just bought it....i'm getting about 32mph now. how much of an increase do you think i'll get?
     
  6. jaguar

    jaguar Well-Known Member

    32 is fairly good already so don't expect too much increase.
    more important is lessening of vibration, better idling, more consistent running, longer bearing life.
     
  7. mountainman_oef

    mountainman_oef New Member

    ok, yea, I'd like 40mph but I realize thats getting a little crazy. haha, so far i've got expansion chamber pipe, ported cylinder, cut on piston, 32t sprocket and soon Jaguar cdi and racing coil. I'm rather happy with my set up. next step is reed valve, upgraded carb, headlight, rear light and turn signals.
     
  8. butre

    butre Well-Known Member

    You should be able to hit 40 no problem if your porting is good, what sort of compression are you running?
     
  9. mountainman_oef

    mountainman_oef New Member

    how do i measure compression?
     
  10. butre

    butre Well-Known Member

    what cylinder head do you have? is it an aftermarket one, or a stock one? if stock, is it a slant head or a straight plug head?
     
  11. mountainman_oef

    mountainman_oef New Member

    stock slant head
     
  12. jaguar

    jaguar Well-Known Member

    No matter what head is there, the only way to know compression is to measure it with a compression tester. There are some cheap ones available for less than $20. I consider having one absolutely essential if you have modified the engine.

    Since you have an expansion chamber then you probably won't get any speed increase. Why? Because the header length determines the top RPM and a CDI won't change that length. Shorten the header if you want more speed.
     
  13. 074KU

    074KU Member

    To measure the combustion chamber size:

    do this ONLY if you feel confident enough and have a few tools.

    Remove the head (only if you have a torque wrench to put her back on!)
    Leave the plug in.
    Lay the head as flat as you can upside down, using a syringe (10cc/ml) drip water into the head 1cc at a time until you just before you form a meniscus.
    or fill the head till you get a meniscus, remove surface tension so water sits flat in relation to the edge of the head and draw it off using the above mentioned syringe.

    Similar to this: http://www.youtube.com/watch?v=QrfEo-Od8yE

    Both of these will give you a combustion chamber size. (fairly accurately)

    To measure PSI:

    If you want to know how many PSI you are generating you need an engine compression tester which sits in the plug socket, give it a crank and it will tell you compression in PSI.

    http://www.mityvac.com/hq_images/05520.jpg (something like that)

    If you don't have one of these perhaps somebody with one and a slant head would be kind enough to do this for you, if anybody offers make sure your engines are modified in the same manner (or not modified as the case may be) as some mods will create higher PSI readings.

    I am sure the is some nasty maths way to figure out PSI from dimensions, I don't know it though.
     
  14. mountainman_oef

    mountainman_oef New Member

    just installed the Jaguar CDI and oh man, its sooooo smooth. I dont feel like i'm riding a weedwacker anymore. Not just the vibrations down but WAAAY smoother acceleration. I'm very happy with this. Next project is building a battery box to put all these wires and stuff in so it isn't all exposed.
     
  15. 074KU

    074KU Member

    May be an idea to open the CDI and stick the Veroboard down with a little silicone to stop vibration damage of the CDI as well. Perhaps your doesn't but mine rattled like a maraca as I got it in the post.
     
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