hello, i am working on a 250 bayou for a friend, it is getting spark and fuel. seems like with each compression stroke it blows it back through the carb. i have the air box off and i stick my hand behind it and the air/fuel blows on my hand. any ideas?

 

check to make sure the valves are seating or not out of adjustment sounds like the intake valve isn't closing all the way.

 

<div class="FTQUOTE"><begin quote>Originally posted by: bigjake34452

hello, i am working on a 250 bayou for a friend, it is getting spark and fuel. seems like with each compression stroke it blows it back through the carb. i have the air box off and i stick my hand behind it and the air/fuel blows on my hand. any ideas?</end quote></div>

The 250 is known to foul a plug easily (when running with the choke on).
Try a new plug NGK OEM plug and see what happens.
Cleaning a old plug does not work well on this quad.