Low profile plug and cap?

Discussion in 'Performance Mods' started by MOTOMTB, Oct 8, 2014.


    MOTOMTB Member

    Hey guys,

    I just bought one of those cool performance billet heads on ebay, everything is cool and I'm all set to ride but because the plug sits straight up, I just don't quite get enough clearance for my gas tank. I'm just wondering if there exists a shorter BH6S plug and cap out there, or possibly just a more low profile cap, that would probably work, all I need is a 1/4" of clearance. Any suggestions, please let me know ASAP. Thanks


  2. butre

    butre Well-Known Member

    get an ngk bpm6a. if you need a shorter plug boot you can just trim the one you've got to length

    MOTOMTB Member

    eh thanks so much man, I owe you one, basically exactly what I was looking for. So will there be any performance difference or is it just a direct replacement but short insulator?
    I think I should be able to take the lower rubber part off the boot so it will fit this plug...
  4. butre

    butre Well-Known Member

    it's meant to be a direct replacement, but I'm sure there's some kind of downside to using the shorter insulator. Whatever that downside is, I've never found it.

    MOTOMTB Member

    Ok, well in this case I have no choice if I want to use the billet head.
  6. Purple Haze

    Purple Haze Active Member

    Get a plug wire with a 90 degree boot.

    MOTOMTB Member

    Lol. it is 90 degrees. The plug itself is too long. Just bought a short one today. Going to try it out.
  8. Purple Haze

    Purple Haze Active Member

    Just trying to help. Lots of people put the straight boot wire on, then have clearance issues. Glad you got er solved. Sometimes these builds come down to a millimeter here or there.

    MOTOMTB Member

    Hey Purple.. don't worry I appreciate it anyway! I didn't have a picture anyway so not your fault :) Big thanks to Brute also for the quick reply. Forums help so much, as opposed to spending half a day running around town searching. I just went to the local utility store and picked one up. Thanks again guys!
  10. HeadSmess

    HeadSmess Well-Known Member

    bpm5-6-7a, brm,bprm, and im sure theres another letter that just signifies the hex size as well. "J" possibly... couldnt be bothered googling anything! and one for the taper seat versus the washer/gasket. now i think thats the J!

    B is the thread, in this case, 14mm.
    P is a projected tip. i personally avoid them.
    M is the size of plug...standard or M for mini :)
    R is the resistor version. i like resistors in my spark plug as well as the cap and the lead.
    the numbers are the heat range, lower for engines that get idled a lot in low temperature climates, higher for ones that get run WOT in the middle of summer.
    the A or more normally H on these engines is the thread length. theres about 1mm difference between the H and A, whereas the "E" is 19mm long or another 6mm+... avoid!

    anything else like IX stuck on the end means fancy electrodes. IX is specifically iridium. if its NGK, anyway.

    all that matters is the b, m, numbers,and the a(or h)

    so a bm8h would do but is more than likely impossible to find!(ngk, for some reason, wont actually list every plug they make...) the one problem with "non standard" plugs is less heat variants available.

    other alternatives are champion CJ8, common mower/yard tool type plug. torch, denso and bosch, the numbers fail me at this point in time...

    at least you had the sense not to get a slant head :)

    MOTOMTB Member


    Wow, you're definately the plug man. Thanks for all the info. I ended up going with a replacement plug for BPM6A, it has some weird number on it, like 5483 or something. Anyway it works fine. I didn't even have to cut the boot, just popped off the lower rubber part and it fit on perfectly.

    Slant heads no good? I've been using one up until now, seemed to work fine.
  12. HeadSmess

    HeadSmess Well-Known Member

    sounds like an ac delco with only numbers..

    only slant head ive had the misfortune to receive on an engine was just the zest on top of the entire freaking lemon the engine turned out to be, so maybe im biased... simply, where the plug goes, rather than "retain" and modify the pattern for the standard head, they made a new one... and skimped on material. where there should be some type of "beam" transferring loads between two studs, there simply isnt. and that was the spot where that head warped every time the thing fired up, despite using a 2.5mm gasket at one stage! 3 sides fine, one side...could almost bend it just by looking at it, uri geller style :jester: the side the plug is mounted in. rather than machine the casting with a recess, they removed most of its strength instead.

    careful fiddling with teflon tape beats metal head gaskets IMHO ;) havent had one ptfe gasket let go yet :) (except on aforementioned slant head...) i cant see the point in making copper gaskets anymore when a loop of tape works better :)