If you want to read a pretty good write up on the why and where-to-for on reading spark plugs then pick up a copy of the current - June 2018 issue of Hot Rod magazine. There is an article called Spark Plug Reading 101 written by a guy - Don Ward - who has been in the spark plug business for 40 or so years. It technical enough to make sense and non technical enough with lots of pictures for those of us - me included- to understand it. Don't get hung up on it being in a car not M/C mag - the basics are there. Might even be able to read it online - I didn't look there since I like paper magazines.
Actually, READING a Spark Plug needs new terminology. I read mine and it reads Champion. Or, some people ask(What does that that Spark Plug say: B8 or B9)? Iv`e yet to hear of a Spark Plug that could speak or read but I would understand the question. Seriously, READING is just fine! Just like Hodaka calls a Hub a Drum. No, the Drum is the metal ring that presses into the Hub. Like a KILL button. If you press it, you won`t die but the engine will stop running. So, why not call it a STOP THE ENGINE FROM RUNNING BUTTON? Your Hodaka DOES NOT have a Motor. A MOTOR is powered by electricity. Your Hodaka is powered by a 2 Stroke Internal Combustion ENGINE. Terminology: It changes over time. Joe Ormonde.
If a "motor" is one that operates using electricity, then I've been buying the wrong oil for the last 55 years for my cars and trucks. Every one I remember has had MOTOR OIL on the label and I've been putting it in my engines. Really, it's a moot argument.
"Motor" is a fairly generic word applied to any device or system which converts stored or potential energy to motive force. When I was a kid, I was referred to as a "motor head" not an "engine head".
And for those that are illiterate, there is a special tool and mount designed to have others inspect and decipher the plug. A company called Webco had made a cast aluminum two plug holder and wrench. It was designed to change out and hold two champion spark plugs so that they could be read their last rights at a later date.
All in good fun and use what works for you!