Shorty Spark Plugs

Discussion in 'Motorized Bicycle General Discussion' started by 2door, Jan 8, 2010.

  1. 2door

    2door Moderator
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    Does anyone have the part number for the NGK-6 in a short, or stubby plug? My local Checker/ O'Riley Auto Parts carries the standard length 6-HS but he says he has no way to look up the short version of that plug without an application. I found several lawn and garden equipment plugs of the right length but all had a very short electrode depth (heat range) compared to the NGK-6.
    I just built a 24" bike and even though the plug fits I have to use an open end wrench to remove/install it due to the close fit. No biggie but its always better to use a socket.
    Tom
     
  2. Dave31

    Dave31 Moderator
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    The only low profile plug I know of is the Champion CJ7Y or CJ8 I believe.
     
  3. 2door

    2door Moderator
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    Thanks, Fair. I'll check those today.
    Tom
     
  4. Finfan

    Finfan New Member

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    Sick bike parts carries 2 short plugs. They list the numbers as NGK BPM6A and NGK BPM7A.

    scratg
     
  5. azbill

    azbill Active Member

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    I have had success with the cj7y :)
    every 2 stroke I have built got 1 (they are cheap at ace, its 10 miles away to an auto parts place :()
     
  6. 2door

    2door Moderator
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    Thanks everyone. That should do it.
    Tom
     
  7. bairdco

    bairdco a guy who makes cool bikes

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    accel makes a cool yellow one, but i dunno the part#.

    i've got the same "problem." 24" bike, open end wrench. if i had a 1/4" less clearance, i'd have to take my motor off to check the plug.
     
  8. cigron

    cigron New Member

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    Im useing E3 make number e3.10 it has 2 threds less the plug that it came with.
    it`s a little more then 1/2 the size. But it runs better then every.
     
  9. 2door

    2door Moderator
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    Cig,
    What brand plug? NGK, Champion, Autolight?
    Tom
     
  10. wantabike2009

    wantabike2009 New Member

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    see if you cant cross reference that plug number with a stilh chainsaw or a weed eater maybe a polan or other brand hope this helps call a small engines shop they may have paper books still to do the cross for you
     
  11. mdlee1958

    mdlee1958 Member

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    2Door,
    I've been running SBP's NGK BPM6A up here in Ft Collins now for about 2 months and has run very well even thru these cold snaps. I too have a 24" frame that has had to have the engine "shoe-horned" in. and the short plug is real easy to get in and out with the standard plug tool.
     
  12. cigron

    cigron New Member

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    2 DOOR
    the brand made is E3 you can find them in most auto parts store the part number is
    E3.10
     
  13. 2door

    2door Moderator
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    Okay spark plug gurus...Take a look at these photos.
    Look at the first one (left) and notice the difference in thread length between the NGK and the Autolite plugs. The Autolite is the crossover from a Champion plug, CJ7Y recommended by those who have used it. It also is a cross for the NGK BPM6A, the short version of the plug many of us use. At first glance you'd assume the longer threads would relate to a hotter plug. I saw the difference in thread length and told the counter man that it wasn't the same as the NGK. He layed them next to each other and told me to look at the reach of the electrodes. To my surprise they are the same. The porcelain is longer, more of it exposed below the threads of the Autolite shorty but the reach is the same as the NGK standard length plug, B6HS...So...is heat range determined by the length of the exposed electrode or the depth at the end of it? Obviously it is the total depth and thread length and porcelain placement has no bearing on heat range. Just curious.
    Tom
     

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  14. mdlee1958

    mdlee1958 Member

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    Since the purpose of the porcelain is to insulate and control the amount of spark I woud say your right 2Door.
     
  15. mdlee1958

    mdlee1958 Member

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    But my concern would be with the additional length of threads will it clear the piston head ? I guess the easy way to tell would be to lay it down next to the OEM plug that comes with the engine and compare the two side by side.
     
  16. 2door

    2door Moderator
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    Actually, mdlee, the longer thread plug is the one I always run in 26" bikes. It is the replacement for the kit supplied plug that many of us use, the NGK-6-HS. There's no piston interference with it. And as far as that goes, the shorter thread reaches into the combustion chamber the same distance. Thanks for the reply. And I neglected to add in my earlier post that I have installed the short Autolite plug and the engine seems to like it just fine.
    Tom.
     
  17. tommyboy1442

    tommyboy1442 Member

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    i have a question,im running a short ngk plug that ive got from sick bike parts,now the reach on the short plug is actually shorter than the stock one supplied with the kit,when its tight in the cylinder head,the plug is actually inside the thread hole and doesnt come out as far as the stock plug.could this give me less compression because of more volume inside the combustion chamber?also could this affect the efficency of the fuel being burnt?id like to hear what some others think.ill post pics soon....
     
  18. wildemere

    wildemere New Member

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    Using the NKG part number guide available here,

    NGK Spark Plugs USA

    A BPM6A decodes as 14mm plug with projected tip and 3/8 long threads

    The B6HS Is the same as the stock plug, 1/2" threads

    BP6HS has the projected tip as well.

    The shorty plug will leave exposed thread in the chamber, not good for many reasons. Especially when you try to install the correct 1/2" plug and the threads are full of carbon or burnt away.

    The shorty plug may fit better without its washer or if the head is machined to accept 3/8" plugs. The quality of the alloy used here might not be good enough for only 3/8ths of thread though.

    One of my engines blew out a shorty plug once.

    A helicoil insert fixed the issue though.
     
    #18 wildemere, Jan 12, 2010
    Last edited: Jan 12, 2010

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