Plug Gap

Discussion in '2-Stroke Engines' started by JimKamenidis, Sep 1, 2010.

  1. JimKamenidis

    JimKamenidis Member

    Spark Plug Issue

    Finally after alot of plug-chops and carb-tuning I got my fuel mixture right..
    At the middle of the spark plug where the electrode is there's a almost perfect chocolate tan color but all around it and where the sparg plug screws there is black oil...
    Is this normal or bad and am I loosing any compression?

  2. GearNut

    GearNut Active Member

    That is normal, and unless you leave the spark plug loose in the cylinder head, you will not loose any compression.
  3. JimKamenidis

    JimKamenidis Member

    you're right! :p
    I've just ordered new spark plug, boot, exp. chamber and high flow filter and can't wait... :)
  4. JimKamenidis

    JimKamenidis Member

    Here's another one.. I usually see recomendations of spark plug gaps ranging from 0.20 to 0.50 but I have mine at about 1..
    I know I have a very high idle but I like high speeds.
    The thing is why haven't I heard nohing like that from anyone else, are there or could there be problems and does that mean that if I make the gap bigger I will have an increase in top speed again??
  5. GearNut

    GearNut Active Member

    The CDI unit is very weak. Forcing it to jump a large gap is only working it harder that it's designed capacity and will cause it to burn out faster.
    Setting the spark plug gap to .024" to .028" seems to be the best range.
    The largest gap factory specified by Grubee is .034".
  6. JimKamenidis

    JimKamenidis Member

    ok thanks you, I just bought an ngk and the gap seems small enough so is it ok to leave it how I got it because I have no way of measuring it.??
  7. HeadSmess

    HeadSmess Well-Known Member

    i confess ive always been an eyeball gapper after experiences with lil particles of carbon getting in an annoying place.... 1-2mm

    the cdi is not weak. they are intended to produce spark at rates of up to 20,000rpm for single cylinder use... far superior to any induction coil/points system. very hot and intense sparks of a fixed length and strength.

    maybe in these engines they are POS(in my opinion, yes)...but...

    at high RPM, whilst the charge time is less, the charging ENERGY is MORE due to increased speed of the magnets passing the coil. the basic laws of electromagnetics. left hand or right hand rule? iunno :p

    Voltage AND Current are proportional to the RATE at which a WIRE "cuts" a LINE of MAGNETIC FORCE.

    the spark is still just as long, and strong, irrespective of speed....within limits. (module circuitry mostly)

    its ironic that cdi is not good for extremely low speed engines! the magnets dont pass the coil fast enough to generate the voltage required...

    you can improve spark energy by using stronger magnets (more lines of force) or more turns on the coil (more wires to cut lines of magnetic force) but then...the cdi module has a regulator built in! so.... you replace the module :) the module contains things like a capacitor and fancy bits of silicon to do the hard work, including spark advance!

    then the upper limit is still restricted to less than 40kv. high voltage starts thinking
    everythings nice n conductive....
    Last edited: Sep 4, 2010
  8. GearNut

    GearNut Active Member

    HeadSmess, By weak I am referring to the components used to manufacture the CDI box, not the KV output of the secondary coil inside it.
    They cannot handle jumping a large spark plug gap for long before suffering internal insulation breakdown.
    These Chinese CDI units do not have an electronic advance in them either. I wish they did, one could pull more RPM's out of the engine and have better low end torque as well.
  9. RedBaronX

    RedBaronX Member

    if you have the chance to go to an auto parts store, plug gappers are available as cheap as a dollar. The ones I have seen that cheap look a little like a large coin.

    my plug gapper was my grandfather's, but I don't know how old it is. (at least 20 yrs)