spark plug gap

Discussion in 'Motorized Bicycle General Discussion' started by nmason, Jul 22, 2008.

  1. nmason

    nmason New Member

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    Recently I put a 80cc chinese engine on my bike, does anyone know what the proper plug gap is? It ran great the first day I tried it but now it runs but doesn't have any power. I was going to put a new plug in it thinking I might have fouled the one that came with it out trying to get it to run.
     
  2. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    .020"

    Check your intake for an air leak.
     
  3. Dave31

    Dave31 Moderator
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    Welcome to the forum :)
     
  4. nmason

    nmason New Member

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    Thanks, I'll get a new plug and check the intake.
     
  5. Ilikeabikea

    Ilikeabikea Moderator
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    Welcome to the forum. Glad you joined us..................
     
  6. Quick1

    Quick1 New Member

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    I just installed my 80cc and my spark plug gap was set to .045 and I adjusted it to where this forum recommended (some said .018-.023 & some said .020-.028). I set it to .025 & it wouldn't start. I tried everything and finally re-set the original gap & it started right up!
     
  7. Quick1

    Quick1 New Member

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    I'm sure it has something to do with the fuel/oil ratio used for break-in. It would probably have to be a bigger spark to fire through all that oil (16:1). It could also be due to the quality of components used. I'm using the stock plug/plug wire and will be changing that pretty soon. I'm learning a lot on the forum, but I haven't been able to find anything about upgrading my plug wire. Just recommendations to upgrade to a 7mm or 8mm wire. Not to change the direction of the thread, but can you point my in the right direction?
     
  8. eDJ

    eDJ New Member

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    Ya know alot of automobile engines are running gaps in the .040 neighborhood too. I think it's more to do with the CDI ignition they are set up for. As far as the plug wire I don't know just what the ohms resistance (per foot) of the wire
    should be, but if you take the wire off and check it with someone who knows and understands this stuff then you could make that calculation.

    I've seen guys put solid metal spark wires on High Energy Ignitions and burn the
    system out. They generally rely on some resistance. The resistance helps to prevent the premature burn off of the electrodes (both center and ground) of the plug and maintain the longevety of the ignition system. Generally the wider gap gave better bottom end and starting characteristics where as the narrower gap gave the best top speed running. Bear in mind motor's aren't designed to run at 100% for long and 75% is a more sane cruising speed.
     
  9. al1971

    al1971 New Member

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    hello everyone new to site have read some great stuff on this site on a spark plug gap which is better if it calls for a range between .028 to .034 a smaller gap seems to make more sense????
     
    #9 al1971, Aug 30, 2008
    Last edited by a moderator: Apr 26, 2009
  10. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    With the weak mag the china in-frame kits have, the general consensus is to gap @ .018-.024

    If you can get a consistant spark at .034, go for it.
     
    #10 Bikeguy Joe, Aug 30, 2008
    Last edited by a moderator: Apr 26, 2009
  11. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    To answer your question, a larger gap will give better low end and starting and a smaller gap misfires less at high rpm.
     
    #11 Bikeguy Joe, Aug 30, 2008
    Last edited by a moderator: Apr 26, 2009
  12. Biker Mike

    Biker Mike New Member

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    It sounds like a lot of people are having this same problem. I have posted this response on several threads where I think the same problem exists.

    Ok, here goes, I had a sputter and power problem with one of my kits as well. It ran great for the first week and then all of a sudden no power and sputter. I finally figured it out after 2 carb's, new wire and end, new CDI, new rings and all. Here is what caused my problem and once done I am riding SMOOTH once again.

    The problem was restricted Air/Fuel flow to the cylinder by the factory intake gasket. It seems the gasket is cut to the size of the intake and not the cylinder. Once the gasket was saturated with fuel and oil it expanded and interfered with the flow.

    The fix: Remove the carb and intake. Cut the intake gasket center hole out using the engine side as a guide (I used an exacto knife). Be careful not to get pieces in the engine. Add blue sealer (small amount) to both sides of gasket and re-install. Mine runs GREAT now.

    I hope this helps. Let me know if anyone needs further info on this such as symptoms,or fix procedures. I love it when a plan comes together!
     
  13. misteright1_99

    misteright1_99 New Member

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    I get a smoother ride with mine set at .030 I have tried everything from
    .020 to .040
     
  14. azbill

    azbill Active Member

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    or you could just use RTV only
    I put it on the manifold and bolt it up
    I do the same with my exhaust
    neither leak and the engine has 1700+ miles since late March
     
  15. HD62

    HD62 New Member

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    I just purchased a 65 cc Chinese bicycle engine. Can anyone tell what the spark plug gap should be on this 2 cycle?
     
  16. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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  17. HD62

    HD62 New Member

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    Thanks Joe
     
  18. Dave31

    Dave31 Moderator
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    Hello HD62, Welcome to the forum :)
     
  19. Gallup

    Gallup New Member

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    What gap for you plug are you using

    Greetings,

    Bought and built my bike (Chinese "80cc" 2 stroke purchased off E-bay) about a month ago and have had no problems at all. Ride to work and back everyday - about 4 miles round trip. I live in Gallup, NM at about 7000ft above sea level and pulled the plug last night to see if it was running too rich. I have not changed the stock plug. When I pulled the plug I noticed that the gap was HUGE!

    What should the spark plug gap on these plugs be?


    TIA

    G
     
  20. Motormac

    Motormac New Member

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    .20 to.25 should be the gap.Throw away the stock plug and replace with a NGK B6HS plug, If you continue to use the stock plug the electrode may break off and cause damage inside the cylinder.
     
    #20 Motormac, Nov 16, 2008
    Last edited: Nov 16, 2008

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