I picked up a yz 250 and Im having trouble with the plug fouling. I ran it for about five miles today then it quit. I checked the spark and had none. Im mixing the gas 42-1. I just picked up the bike and Im just now going through it. Its been a few years since Ive had a bike. The last yz I was a 78' 400. Its a upgrade for me having a 91. Should i rebuild the carb? Is there an adjustment I can make to solve this problem?

Marlin

What condition is the plug in when you take it out? Often the mixture is off.