I started up the GTR after storage yesterday and she ran like a champ. At the end of last season I changed to hotter plus for two reasons: (1) I thought it might help in cold weather up here in Minnesota and (2) I had wet, charred plugs.

My motor seems to start faster and run better with less backfire. Is this coincidence? Could I have gotten the same result by adjusting the carb? What is the guide for which plug temp to use?

Thanks

The operating temp of your engine (which is why you choose a specific temp plug) isn't affected by air temps in the sense you're thinking. A hotter a colder plug should be chosen based on achieving certain temp ranges inside the cylinder for combustion. Too much heat on the plug tip can cause all sorts of damaging issues, too cold can prevent efficient burn, increase fouling, and have less power. You may have gotten lucky and found the correct plug. Just for the wrong reasons.

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For the record, I went to a colder plug once I built my engine. Havent played with plugs since.

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Maybe, but the plugs are just a piece of the puzzle. If the engine is tuned correctly (air/fuel) then changing plugs might be a good idea or not, and might require an tweak of the screws on your carb. Jet sizes shouldn't change with a plug change, but the temps would and could make the engine a bit happier or not for the long term.

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