Here's my issue. It was running fine one day then the next it stopped running properly. It will crank when no one is sitting on it but any pressure pushed on it downward makes it shut off. Also when you throttle up when it's idling it starts stuttering with a drumming sound and shuts off. I decided to do an oil change and a gear oil change to see if that'd help but it didn't fix the issue. I also checked the air filter to see if it was dirty but it's very clean. What should I do next? Thank you.