250r with 310 kit, what plug heat range?

[WEATHERBY460]

86 atc 250r with a 310 big bore kit, paul turner exhaust...should I run a br8es, or a br9es?

Thanks

[nate b]

your motor is the only thing that can answer that question. I'd start with a 9 and pull some plug chops and see what the plug looks like.