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Q: I bought a used 96'Gas-Gas. What sparkplug should I run in it? It's got a NGK B7ES in it now.

A: That's not the right plug. It's too 'cold' and for a MX bike. Check your owner's manual or your dealer to see what they recommend. Here's some plugs that work well, in most conditions, in your bike: NGK BP5ES, BP5EV, Bosch W8D, WR8DP, Champion N11YC. Set the gap at .024 in.

Most rider's have a 'pet' plug that they like and opinions vary. Some rider's 'hate' American (or German, or Japanese) plugs, some love them. I've used both, however, I like platinum type as I've found they run a little 'cleaner' but they cost a little more.

Those numbers and letters refer to the size, length and thermoconductive efficiency (ability to dissipate heat) when in operation. In Trials, we run 'hot' plugs that run cleaner under the operating conditions we subject them to (low rpm, partial throttle, etc.). Keep in mind that the heat range rating (usually the number on the plug) is different for American plugs and European/Japanese plugs. The higher the number on an American plug (like a Champion) the 'hotter' it is. The lower the number on non-American plugs, the 'hotter' it is. That's the reason the '11' Champion is roughly equilvilent to a '5' NGK. Some factories recommend a resistor type plug. As I understand, this is for reducing radio reception interference only and you can run a non-resistor plug in most bikes without any problems.

Don't forget to check the plug often for any unusual signs of problems such as a lean fuel mixture (pump gas should give you a milk chocolate color, however some race gas gives a dark gray color), broken or chipped insulator, blued threads (overheating), etc. Knowing how to 'read' plugs is a good way to 'see' into the combustion chamber and get an idea as to what's going on in there.
Professional tuner and 'Trials Competition' writer Jon Stoodley has very kindly stepped up to the plate to answer your questions. If you're having problems, or need some advice just send an email to Jon. If it's something that could be useful to others, we'll post it on the site.
This article originally appeared in 'Trials Competition', and was reproduced with permission.
Home. Back. ..... The Gas Gas Guru. Technical Information.