Spark plug heat range.

[DAM shop]

What do you all think about a hotter spark plug to help burn excessive carbon and fuel off? One of our trikes likes to get the plug pretty wet and I thought a hotter plug might help. Runs great.

[ATC200X4716]

Is the porcelain inside the plug around the electrode black and wet? The hotter heat range plug won't hurt, but it may not be enough to overcome excess fuel at some power condition. Good idea to start with a fresh plug and see how it changes color. Seems like it is a little rich somewhere in the operating range. Maybe try dialing down your fuel mixture at idle and make sure the engine responds, either slowing down or dying out. Just remember how many turns you move it so you can put it back. What kind of machine? If it's good at idle maybe check your jet sizes against the shop manual, but also have to be weary of drilled jets. Is it using any oil? it could be some oil getting through the rings and valve seals wetting the plug but you should see or smell some smoke. Make sure to take it for a good long ride to get it hot and run it to dry the plug to temp, and drive it in above idle and kill the engine if you want to get a gauge of how it is burning above idle. You can do the same letting it run at idle for a long time and then pulling the plug to try to get a gauge on how your idle burn quality is.

[patriot1]

"What kind of machine?"

Bet it's a 90!!

[DAM shop]

"What kind of machine?"

Bet it's a 90!!
Bored and stroked 110 with a 24mm mikuni. I would attempt to rejet but it runs great in all power ranges. I just have to start it right in the first few pulls or I’m pulling the plug. I assume it’s a bit rich.

[rpeters]

Far better to jet it properly than to use a hotter plug than stock as a band aid to compensate for some other problem. A hotter plug is not hotter than a colder plug until the engine is running, therefore, a hotter plug will not make the engine start any better, and if it has a "big cam" etc, you will likely never get it to start easily continuously even if it is perfectly tuned. Also, if an engine has much more dynamic compression than stock, a colder plug is typically used.