DYT4000 backfires when running

[kjhansen]

My Craftsman DYT4000 with the V-twin Briggs and Stratton 24hp engine (445777) backfires all the time when running. Starts OK and runs good for about 30 seconds, but then backfires constantly--unless it's at full throttle and the blades are engaged on the mower. Then it seems to smooth out--or maybe I just can't hear it because of the combined engine and blade noise. Anyway, I've replaced the bowl gasket and the needle in the carb (plus cleaned the carb out), put a new air filter on it, replaced the spark plugs, replaced the breather tube (it was split all the way up one side), and it isn't any better. Cuts OK and seems to have good power when cutting. I'd just run it the way it is, but the backfiring can't be good for it.
Keith

 

[kjhansen]

Interesting. 88 views, no responses. Well, anyway, after all I'd done I decided it might still be either bad gas or a dirty carb. So I put some Heet (alcohol based to absorb any water that might be in the gas) in the tank, started it and sprayed carb cleaner down the throat of the carb while it was running. Now it runs like a champ again. So if you get an inexplicable constant backfire you might want to try those things first.
Keith

 

[mechanic mark]

Good post Keith.

http://www.briggsandstratton.com/us/en/support/faqs/engine-backfire-afterfire information for you to read.