I picked up a DB30 at Walmart for half price that had been returned because it had issues. It had a sign on it that said it would idle but stalls when given gas. I stopped and got a new spark plug on the way home and swapped it out before I even tried starting it. With the new plug and started right up and runs, but I don't think it's running right. I rode it around the yard and it doesn't move very fast, I would guess maybe 5 mph. Going up a slight incline pretty much brings it to a craw. I am about 260 lbs, so I wouldn't expect it to move very fast, but I would think it should be a bit faster. If I pick up the rear end and hold the throttle open it seems to run good. Any advice on a good starting point to troubleshoot? Thanks in advance.