You guys are all wrong on what Heat riser is for.
First it is closed when cold. It blocks the exhaust from going out the pipe more and redirects it to the intake to warm that up and the carb with it. Then, as it warms up the coil gets warmer and the riser opens slowly to unblock the exhaust and run it clear thru with no blockage. By then the intake and carb should be warm enough to run correctly. Yes, in cold weather w/out it, it takes a long time to warm up. It does NOT change the choking or such on star-up, but may need to run on partial choke longer before warming. The riser does not "flap" around while running, it's closed or open.
