Hey everyone i just had a top end rebuild on my 1989 honda cr250. I can not get my bike to start it has fuel,spark,and great compression.The spark plug is not fouled and the top end rebuild was done by what he calls himself a proffessional. The bike has always had the problem of fouling plugs like 10 minutes of riding we have set the bike up 32:1 sometimes it backfires sometimes it dosent.The air screw is set at what its supposed to be.Can anyone help me plz thanks.