How do you stop flames from coming out of the tailpipe of a 1980 Harley Davidson FLT?

Go get it checked on the dyno to see if you are running rich,which u probably are. Minor carb adjusting should take care of that. You more than probably got a leak and she's sucking air in at the flanges. They got some stainless stel sponge gaskets now that do a pretty good job. You're gonna have a little raw gas in your pipes pretty much no matter what you do but if you're running rich, yeah you need to look at it. Try that S&S shorty. Those go good on Shovels. Looks cool, huh?