Spark plug gap

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Jul 10, 2008
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I read something posted on a thread recently about eliminating a backfire problem (which I'm currently dealing with, BTW) where it was said that one should be sure and check the gap on your plug is at least .030? I've been gapping mine at .025. Is this correct? Currently using NGK BP7ES plugs and an electronic ignition. Does forcing the plug to jump a bigger gap make for fewer unintended ignitions or something like that, perhaps?
Boyer recommend 0.025" as did Lucas for their points system, others might prefer 0.030". I don't think you would notice any difference if you used either gap.
I just has a mechanic tell me that Boyer likes a smaller gap than with points. He recommended .18 to .20 for gap with a Boyer ignition. Any comments?
I've used .025" with a Boyer and N7Ys for as long as I can remember. Never had a problem with fouling or difficult starting unless there was an external cause. Try holding an HT lead near the head. The Boyer can jump far further than 25 thou.
Backfire sounds like a carburetor problem to me. Check your pilot jets; chances are one or more is partially blocked.
Yeah, I figured that a too-small idle jet was part of my problem. I replaced it with a larger one and the problem has gone away mostly, but I get a pop every now and then, and mostly on decelleration. I've made sure the exhaust is good and tight, and made sure all adaptors and connectors on the intake manifold are air tight. It still appears to be running a little lean, and I'm thinking the exhaust valves may need re-lashed (I had them reseated recently) or I still have more jetting to do.
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