I have a 2009 Ferris IS1500z 48in with a Kawasaki 21 hp v-twin. engine model number: FH641v-ES25-R. the mower and engine only have 200 hours. About a week ago i was cutting a yard when the engine simply stopped, after it stopped i tried to fire it up and it simply would not. White smoke came out the exhaust while i cranked, and after a few seconds of cranking a large flame came out of the exhaust and continued to burn for a few seconds. After the flame had entered back into the exhaust it burned inside the exhaust for another five seconds. After that i let the mower sit for 2 hours, when i came back to get it it fired rite up, and i put it on the trailer. I thought the plugs could be bad since there was probably no spark since there was unburnt fumes coming out of the exhaust. So i replaced the plugs, the original plugs were very black and appeared to be fowled out. I also replaced the hydro fluid just because the mower was due at 2oo hours. after all that was done i went and cut two yards successfully, when i put the mower on the trailer after the second yard, it died and did the exact same thing as it did before by having a large flame come out of the exhaust. So here i am asking what you guys think. I have no idea what it could be. keep in mind that the temps here have suddenly gotten cold again, about 30 degree lows. THANK YOU!