There are many things that can cause this issue. It could be that the timing is not set correctly or that the timing chain or belt is stretched causing the car to be out of time.
running lean can cause your 400ex to backfire ..if it backfires on deceleration its lean ...if it pops on acceleration its running rich.====carb issues
Backfire flame arrestor
backfire flame arrestor
backfire flame arrestor
if it backfires when driving most crank sensors cause this
Your car backfires when you need a new transmission,or tune up. How do you know the difference? Simple...if your car backfires then wont start, or wont start and then backfires,you need a transmission. If it backfires, and then starts moments after, you need a tune-up. Glad to help...David
sheared flywheel key. youtube has vids... type in mower cord backfires & you'll see instructions on how to fix it.
If any car backfires it is usually due to retarded timing, running lean or a problem in the valve train.
If it backfires after you shut it off then it is probably running too rich. Any unburned gas the that is exhausted out and into the muffler will explode with a backfire. With a 1990 model you won't have the anti-backfire solenoid on the bottom of the carb like the newer ones have. If it backfires while it is running it might be out of time. Check the keyway between the crank and flywheel to make sure it is not partially sheared.
while driving yur car reduces speed then pulls off with speed and backfires what can cause that
If it backfires while you are driving, the intake manifold bolts may be loose or the gasket may need to be replaced. If it backfires when you turn off the ignition, the fuel mixture is a little on the rich side.
Type your answer here... It backfires because it is a Briggs and Stratton - replace it with a Honda or Kholer.