Rzr has been sitting unused inside garage for about 18 months. Engine started and run about 15 min every 1 or 2 months. Never any problem starting or running. This week took it out of town to ride for a day. Loaded, unloaded with no problems. After unloading went trailing. After about a 1/2 mile we went down a small kill and started up another hill and engine died. Restarted many times and died each time after only free seconds. Brought it home and started several times with same outcome. Changed to fresh fuel and started it. Lasted about 90 seconds (at idle) and died. So we started it several times and revved the engine up and it continued to run (while still revved up) each time until we dropped it back to idle and it died each time. HELP! Please.