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Weird spark plug color...

Use this area to post problems that may arise, if you could use some help in figuring out what is wrong with your bicycle motor and what needs to be done to achieve top performance.


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Old 07-12-2013, 08:15 PM
Pedrito0906 Pedrito0906 is offline
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Default Weird spark plug color...

Hello riders, this thing is driving me crazy, I've searched for this topic and is impossible for me to find any good advice. I've had a motor around 7 month, I have a NT speed carb, port matched, modded piston, the only thing is I cannot find that right carburetion, that chocolate/tan color in the spark plug, I was using a ngk BH8 spark plug and it was black with a 66 jet no 4 stroking, now I'm using a BH6 and is grey (see the pic) with a 70 jet and no 4 stroking. I have a slant head with a smaller combustion chamber to increase the compression a bit. I live in Puerto Rico where the ambient temperature is around 80F - 100F. I'm usining AMSOIL, 50:1, Please help me to find the right color in the spark plug. Any suggestion will be highly appreciated :-D
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Old 07-12-2013, 08:24 PM
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Default Re: Weird spark plug color...

Not to worry. Your oil and gasoline have much to do with the color of your plug. I'm an Opti-2 user and my plugs all look very much like yours. I tune by shades of grey, which is all I get running the Opti-2 oil at 100:1. If my plugs are dark grey, I lean the carburetor. If they're light grey, I richen them up a little.

Some members have actually reported they get plugs with a red color and it has been traced to certain additives in the gasoline they use.

Tune for the best performance and watch the plug to make sure you don't move into the very light grey shades. That might be a little lean. As long as the engine is running good for you don't worry too much about plug color. A little 4 stroking in mid range is a good thing.

Tom
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Old 07-12-2013, 08:53 PM
Pedrito0906 Pedrito0906 is offline
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Default Re: Weird spark plug color...

Thank you for answering tom, should I use the bh5 spark plug or the bh6 spark plug according to that temperature?
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Old 07-12-2013, 09:27 PM
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Default Re: Weird spark plug color...

Pedrito,
The plug's heat range, signified by the number, 5, 6, 7, determines the depth or reach of the plug's electrode into the combustion chamber. Typically a cooler plug (higher number) will perform better at higher ambient temperatures such as those you'll see at your location nearer the equator. A hotter plug, 6 and 7 will give better performance in cooler temperatures.
The 6 is a good mid-range plug that seems to be the choice of most builders. I've also had good luck with the Champion 811 (L82C) spark plug.

You'll need to experiment and see what works best for you. Your riding style and carburetor tune will play into the way the engine performs. Keep in mind that we always recommend that you accrue at least 200, preferably 300 miles on a Chinese 2 stroke engine before worrying too much about optimum performance. They are a little slow to break in and only after a few miles will they really begin to tell you what they want/need.

Tom
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Old 07-13-2013, 12:41 AM
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Default Re: Weird spark plug color...

Unless your compression is a lot higher than stock, I would use a NGK B6HS. BP6HS would also be worth a try. The only difference is the BP has an extended tip. If your compression is higher than stock you could try a 7.

I think your jet is rich. Try a 66, and be prepared to go as far down as a 60. What you're going to need will depend a lot on how good your exhaust is.

Also gap your plug @ 0.025"
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