All 2st Spark plugs: differences

Hi, anyone have any thoughts on Spark plugs for the WR125? Stock is a B9EG (I believe), would a B8EG hurt, help, or be hazardous for the motor?

Just to confirm, B8EG is a hotter plug, right?

thanks,
JS

The 8 is hotter, with NGK the higher the number, the cooler it is.
If you run the bike hard, high rpm, the 9 is better. If your wife is lugging around, the 8 may be better. Depends also on your jetting, just keep a watch on plug color, and it will tell you which way to go.
I am currently running an 8 in tight single track, but that might change as I get the PWK the way I want it.
GP

Thanks. I fouled the first plug with the bike last weekend following my father-in-law around at walking pace for about an hour in 80 degree weather. The only plug I had was an 8 from my 250 (not the BR8EG, but B8EG), and the bike seemed much happier. It would not load up as much, until I was able to put a smaller pilot jet back in at the truck.

Why would you not want the hotter plug when riding full throttle?

JS

It can burn a hole in your piston in a worst case scenario.

The 'R' designation only means its a resistor type plug so it wont cause radio interference. I'm pretty sure the Husky spark plug boots are also resistor type, so no need for an 'R' plug. Although it wont hurt anything to use one and they are more readily available.