SPARK PLUG TECH TIPS

Generally speaking, you want to run as wide a plug gap as possible. Having to reduce the size of the plug gap once it has been well established can possibly been an indication of problem manifesting in the ignition system. This is common in the magneto systems as they generally need smaller and smaller plug gaps as the magneto deteriorates.

A spark plug that appears to have a pinkish hue to the electrode has either been overheated or has been subjected to pre-ignition. Pre-ignition is the result of the cylinder firing before the plug fires. Carbon buildup, untrimmed gaskets, sharp edges, too hot of a plug are just some of the causes.

Little black splotches on the insulator of the plug can be caused by detonation, which is basically an explosion in the cylinder after the plug has fired. Shitty fuel, too far advanced timing, engines that have seen a lot of miles, or were improperly assembled can suffer detonation when oil gets into the combustion chamber and reduces the octane of the fuel. If that happens, a rebuild is the only repair, otherwise retarding the timing, and/or using better fuel usually does the trick.

Aluminum deposits on the plugs means that the piston is overheating. This is caused by either a lean mixture, or having the timing too far advanced, or a combo of both.

When you have the head off, check the projection of the plug into the combustion chamber. If there are threads showing you will want to either use washers to pull the plug back up or better yet switch to a shorter plug, if possible.