A cap is $4 Coil is $100 start with the cap. the ignition components do fail so having extras is never a bad idea if it turns out that’s not the issue.
On 91 non-ethanol fuel you should expect detonation - and probably rapid engine failure.
Use 93-octane fuel with 10% ethanol, use a 24:1 oil mix.
do i need to clean the carb after each use with ethanol?
I just drain mine and have very few problems with ethanol. I take the airbox and fuel line off, start the engine, idle it until it starts to rev up, then slap my hand over the carb to stall it out.