1981 250r plug problems

[little ricky]

Hey guys i just got a 1981 250r i rebuilt it. But now everytime i ride it kills the plugs ive tried 8's and 9's. Any ideas on why it could be doing this?? anything will be helpful thanks

[dcreel]

Is it running rich? What do the plugs look like when you pull them out?

[little ricky]

Not that i know of. And the plug is like a brown or grayish tan color.