I have used my 8N for 15 years without much trouble. I am now having an issue and could use some advice. The tractor starts and runs fine but after about 5 to 10 minutes it quits. It restarts immediately but quits again. I have drained the gas and replaced the filter and can not see any evidence of rust or other foreign material in the gas. It has a front mount distributor. I was told by someone that it could be the coil. Any suggestions on how to proceed.