Replaced the Factory Plug on a 66cc China Girl Motor -Wow!

Discussion in 'Motorized Bicycle General Discussion' started by Russ McClay, Mar 2, 2013.

  1. Russ McClay

    Russ McClay New Member

    Jan 21, 2013
    Likes Received:
    Yes. It is almost a mantra here to change the factory plug for a better one.
    I decided on an NGK BP7HS - 5111 for a variety of reasons. Unfortunately
    that plug is difficult (impossible?) to find here in Taiwan. So I bought one from
    MFG Supply in the States. It arrived yesterday.

    I already have over 350 miles on the bike with the factory plug and it has
    worked well. Idling no problem. Plenty of power. But I wanted to follow the
    advice of changing it.

    Eagerly I installed the new plug. I don't have a feeler gauge, so I didn't
    bother gapping it. Visually the gap was the same as the factory plug, which I
    also didn't bother gapping. According to NGK, the factory gap is: .027"
    (0.7mm). And since the threaded end is shipped with a cardboard cylinder
    protector around the threaded's highly likely that's what the gap is.

    Fired it up...first thing is the idle was too high! I had to back out the carburetor
    idler screw a full turn out right away. This meant the plug was igniting
    fuel more efficiently (which of course translates to better fuel economy, more
    miles/kilometers per gallon/liter).

    It was raining so I didn't take it out for a run.

    But today I took it out...and whoa...the difference between the performance
    is remarkable! I ride the same set of steep mountain roads with their
    switchbacks almost daily. So based on my digital speedometer I know very
    well what my average speed is on the steeper sections. These are sections
    where I usually have to add a little pedal power (at around 13 mph) to keep
    the momentum a 2-stroke engine needs.

    Well after installing the 2 dollar NGK plug...the machine is powering at least 2
    mph faster in all gets up to speed faster. The combustion sounds
    better. More robust. Better performance. Better gas mileage. Overall a
    significant improvement just from changing the plug.

    And here's the sweet understated benefit of this NGK plug: the factory plug
    has two thin, hard steel washers which have a gap at the ends. The only leak
    (very minor) I've had on my engine was from the spark plug. The NGK plug only
    has one washer. It is thick and tapered and is "soft". When you tighten in
    the plug that washer "melds" with the head. Perfect seal! if you're a newbie like me...take heed to the old-timers here who
    say replacing the factory plug with a better plug is one of the first things you
    need to do!

    Motor on!

    Attached Files:

  2. Russ McClay

    Russ McClay New Member

    Jan 21, 2013
    Likes Received:
    Re: Replaced the Factory Plug on a 66cc China Girl -Wow!

    By the way, that's a 2000cc bottle of gasoline/oil mix in the basket. lol

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