I have a 3hp briggs with a pulsa-jet carb. I bought it not running, and after removing carb, cleaning it, sealing diaphragm with gasket sealer, it runs. But, its very hard to start, sometimes it will idle good, sometimes it won't idle at all. When i give it throttle, it dies. This doesn't happen when the bike is up on stands with the rear wheel free to spin, as it runs nearly perfect on stands. After adjusting idle mixture screw, it ran well enough to ride. It ran crappy at half throttle, but once it reached higher rpm's it ran great and pulled strong. I came to a stop and the engine died. It wouldn't start after that. Just wondering if there's anyone that may know what's causing this?