fe450 misfiring help needed

hi guys out at the weekend and my friends 2006 fe450 wouldn't quite fire back up after we stopped, eventually we got it going again but it didn't want to idle and was shooting out big yellow flames.
we decided to call it a day after being out in heavy snow and managed to ride it home, he's given it a crack today and its still missing and shooting the yellow flames.
im going looking at it tomorrow but its already recently had a new plug and cap and the air filter is religiously cleaned and lightly oiled.
im thinking about taking the float bowl off and cleaning the jets out but any other suggestions to look at?

Hi bud thanks for replying, it was running fine and had been ridden every weekend but we was out and about when it just started misfiring.
I stripped carb yesterday and cleaned it all up and reset float level although everything looked pretty clean, rubber boots all fine too.
The mixture screw was set at 2.75 turns out and clip in the 6th down, I reset the mixture to 1.5 and the. Gave it a try again when built back up, seemed better but everytime I revved it it shot a flame out the back again and that hanging idle was intermittent so tried to would put the mixture screw again and got to 3 turns out before I gave up as I thought that was too much.
The jets are all cleared blown out and stuck a needle in the holes too, just confused with it now!