04 eton viper90 won't start
The 04 Viper 90 should be a 2 stroke engine so valves aren't a issue. My son has the same quad and it did the same thing one time. The oil injector system has been leaking and it leaked into the carb and engine also. I pulled the drain plug out from the bottom of the carb and let it drain out which was very oily. Then I turned the gas back on and let it run just for a bit. Put the plug back in and it fired up. Ran very smokey for a bit and tehn cleaned out and ran fine after that. I still had the issue of the oil injection system leaking which I will address later but it has bigger problems now. After a pretty good over the bars fall, the rear swing arm is bent with about a 5 degree twist in it. I am working on that now.
Let us know what you find out and good luck with it!