Honda Interceptor 1987 Spark Plugs getting carbon fouled within seconds. Vehicle idling louder than usual

I recently installed a new engine on my Interceptor. After riding for about half an hour the bike petered out. I left in in the garage for about 7 months before installing new spark plugs. This got it running again, but it idles extremely loud, as if I was cranking the throttle all the way, and the plugs become carbon fouled within seconds. I tried to start the bike up the next day and it wouldn’t work until I’d put a fresh set of plugs in it. What might I want to inspect? Is it safe to keep a bike running if it’s idling so loudly?