Steve........you do know 8N's have 2-differnt dizzy's don't you??? the weird 4-nipple frontmount with 1-terminal square ignition coil; and the more common looking 5-nipple sidemount with semi-bulletproof round can ignition coil.
A BAD condenser will show-up in the FIRST 1-minute of operation. NOT YER PROBLEM. Keep yer itchy-twitchy fingers off'n them handy-dandy carb tweek'ums.
Dont't fergitt, yer N-tractor fuel system is gravity feed and 2-hrs of operation could create a VACUUM in the fuel tank which could self-relieve inna'bout 1/2-hr. Never hurts to un-snapple yer gas-capple when yer tractor stalls.
The squarecan ignition coil of the 4-nipple dizzy will generally run fer about 1-hr before the INTERNAL insulative tar melts and causes WEAK SPARKIES just as you complain. It takes about 1-to-4hrs for the internal insulative tar to re-harden and make strong sparkies.
The ONLY cure fer melted squarecan ignition coil is REPLACEMENT. Unfortunately, many neubie shadetree mechanics BYPASS the "infamous ballast resistor" for hotter sparkies and eazier starting. And then guess what??? MELTED tar and weak sparkies. Both the original 6V and the modern 12V squarecan coil NEED the MANDATORY ballast resistor. NO ARGUE!!! ..........Dell, yer self-appointed sparkie-meister