NGK Spark Plug Test

Discussion in 'General Questions' started by Fabian, Sep 16, 2009.

  1. Fabian

    Fabian Well-Known Member

    After reading posts on the superior performance of NGK spark plugs, i decided to do a basic test.

    I chose three spark plugs: an unknown plug out of a chainsaw, an NGK BP6HS and an NGK BP8HS-10.
    The BP8HS-1 is the same type of plug as the BP6HS but 2 heat ranges cooler and the "1" designates it has a 1mm electrode gap.

    The chainsaw plug must be a reasonably cool plug like the BP8HS-10 and the BP6HS is a hotter plug as evidenced by the clean burn on the electrode.
    I was surprised just how much hotter the BP6HS ran that the BP8HS-10, a bit too hot in my opinion.

    I'll be sticking to the BP8HS-10 as the engine seems to run a bit smoother and the burn colour is a bit more comforting than the BP6HS.

    The conditions for the test were wide open throttle with an untouched factory assembled carburettor and 98 octane unleaded fuel with 20:1 oil ratio.
    The new plugs were run for approx 10 kilometers or 6 miles before the photos were taken.
    As i tow a modified bicycle trailer weighing 25 kilos; i'm always running at wide open throttle, uphill or downhill because i've installed a SickBikeParts shift kit.
    The engine does not get over revved but it works awfully hard towing the extra weight.


    Attached Files:

  2. Pablo

    Pablo Motored Bikes Sponsor

    What is your jet size? Looks like you might be a little lean on fuel.

    What oil and ratio?

    How have ambient temps been at the end of winter?

    With my slant head I have been running a BP6HS for awhile now and the plug looks a lot like your BP8HS.
  3. Fabian

    Fabian Well-Known Member

    I agree with you, the BP6HS does appear to look like it's running lean.
    Having said that, the other two plugs tell me the mixture is ok - i'll be checking my jet size to confirm the carburettor is set to factory specifications.

    What exactly is the correct jet size and what jet size are you running in your 66cc engine.

    On the day of the plug tests, ambient temperature was approx 20 degrees celcius, that makes it around 45 to 50 degrees farenheit and humidity was low.
    When i use the standard Chinese sparkplug, the burn coulour looks like the BP8HS-10 in my engine.

    I'm really surprised at how much difference spark plugs make in these little engines, maybe not in outright power, but controlling the flame kernel temperature.

    Oil ratio i'm using is 20:1 - slightly leaning out the air fuel ratio over say 25:1 or 30:1

    I can't afford to jet richer as the engine is drinking fuel (towing the trailer) thinking petrol is the price of water.


    ps since my modifications to the final drive train to rear cassette and derailleur, i've had 100% reliability for nearly 1000 kilometers and the Jackshaft Shifter Kit is working beautifully - just awesome to have gears.
    All we need now is a 2 speed hub built into the chainwheels, giving a crawler gear for hill starts on very steep grades and a fully loaded trailer.
  4. Ghost0

    Ghost0 Guest

    You know we have a 30 tooth with an offset so if you have the room you can run 2 chainrings with a front derailleur. Then you will have super low gears.
  5. Fabian

    Fabian Well-Known Member

    That's exactly what i need - combine it with the new Shimano 12-36T and i'll have the crawler gear i've always dreamed of.

    How does the offset 30 tooth chainwheel attach to the 36tooth chainwheel - any photos?

  6. Ghost0

    Ghost0 Guest

    It just bolts on inside the 36 tooth. Here are some photos of one of our customers that installed it.

    Attached Files:

  7. Fabian

    Fabian Well-Known Member

    Oh yes - that's exactly what i want.
    When i bought my SickBikeParts Jackshaft kit, i didn't even realise the 30 tooth chainwheel was "an additional" chainwheel - the website needs to spell it out in big letters.
    Running a front derailleur may have prevented my chainsuck problems back in the early stages of the trials and tribulations with chain, rear wheel and rear derailleur destruction.