Sparkplug Indexing??(Slant)

Discussion in 'Motorized Bicycle General Discussion' started by Mac, Jan 23, 2010.

  1. Mac

    Mac New Member

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    I was wondering if indexing the spark plug on these engines is a worthwhile endeavor. Both of my PK80 Slant motors with NGK's (or stock) have the outer electrode facing down, basically shielding the direct spark from the piston. I'm thinking facing the piston = Better. Anyone's thoughts??
     
  2. tommyboy1442

    tommyboy1442 Member

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    whats happenin mac,if it matters,in my opinion, i dont think it matters much,i used to think like that as well,but then i thought about it one day and figured it doesnt matter cause its the vapors that ignite and they are probably around the entire voulume of the combustion chamber. i wonder has anyone tried an irideum plug in these motors yet? i had a 94 cavalier with 2.2 motor and noticed huge throttle response improvment with an irideum plug by ngk.....
     
  3. Mac

    Mac New Member

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    I know in the drag racing days we used to always index the plugs(BB Chevy) good for a bit more power. My last engine dyno, the operator did it too(Car engine) but that was a 12 1/2 : 1 compression, Heck I'll give it a try, I don't have any shims that fit these plugs, I'll pick some up when I get down to the speed shop. I'll post when I get results, even though it's only "seat of the pants".
    xct2
     
  4. WayneC

    WayneC New Member

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    I always indexed the plug TOWARD the intake valve. Where exactly is the intake valve on YOUR engine?
    Point the plug in THAT direction!
     
  5. Mac

    Mac New Member

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    It's a 2 stroke, PK80.
     
  6. bairdco

    bairdco a guy who makes cool bikes

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    i do it, just because. dunno if it helps, but i know it doesn't hurt.
     
  7. pdubs

    pdubs New Member

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    straight from NGK's website.

    4. Indexing

    This is for racers only !!
    Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.

    However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.

    In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.
     
  8. pdubs

    pdubs New Member

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    so on a 3hp engine you can expect 0.03HP??
    guess its something you want to try just for the hey of it ;)
     
  9. Mac

    Mac New Member

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    OK so I indexed the spark plug, outer electrode facing up, only took .040 shim. No other changes, before and after runs, Same warm-up distance from cold. I noticed it came on the pipe quicker on top end, before run it 4 stroked lightly, didn't clear out for about 10 seconds, cool down, reindex to "unshield" spark gap, same warm up, it 4 stroked right on top end a bit, like 1 second, then cleaned right out. I know that's not scientific but I tried to keep test as consistent as possible. Heck it works for me!

    Mac
     

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