Need some mechanical info Honda gx390 belt driven

Alright I started a small pressure washing business. I have about three years experience but just got back into it. So I purchased a Honda gx390 belt driven. Went to do my second driveway job and noticed a funny sound about halfway through the job. I also noticed I lost some psi. I checked the oil and pump oil, everything was good there. Then I pulled the belt cover just to see if there was anything there. Sure enough the pulley connected to the shaft coming from the motor was about to fall off. I found a square key or shear pin whichever it’s technical name is laying in the cover. So I don’t have a ton of mechanical knowledge but I noticed the shaft was thread and turned the pulley to see if it would tighten back up and it does. Being the machine is under warranty (1 week old), I called Honda. They said to take it to a certified Honda engine repair shop 45 minutes away (closest one). So my question is this… The pin or key whichever it is doesn’t appear broken. Can I just tighten up the pulley, insert the key pin and turn the pulley back out to tighten it all up or do I just need to drive the hour and a half round trip and get someone to fix it.

I don’t pretend to know about that exact circumstance, but if the key tightens back on and the pulley is secure, sounds like you fixed it. I would however use some blue loctite to prevent it from backing out again.

Thanks. Crazy thing is I spent a little extra getting belt driven in hopes of not having any issues.