rode the atv one day it ran fine. put it in the garage and the next day it would not start. turns over and backfires but will not start. has spark and gas. is it possible to jump time?  

yes it is very possible and with it backfiring it sounds like it has.

could be the cam tensioner broken.  

i checked the timing it is correct. where do i go from here? i put a new ignition module a couple of months ago. what else could it be.  

how much compression are you getting?

get a guage and see what your compression is.

could be a bent or broken exhaust valve.  

what should the compresion be? the atv has very few miles on it. less than 400  

well it varies from atv to atv.

a 400 should be getting anywhere from 150 psi -165 depending on the design.

i don't have my books with me or i would look it up for you.
give the dealer a shout and ask them, they should be more than happy to tell you how much compression you should be getting.

the backfiring it is a backfire or more of the engine trying to start?

a backfire should be loud.
whereas if it is just trying to start it wont be as loud but just sound like it is trying to start.  

it is a very loud backfire through the exhaust. appears to have good compression with the old finger test. but have not put a tester on it.  

yeah i'd check the compression with a guage.

you could have a bent or broken valve, if it is under warranty take it back to the dealer.