B&S 5hp backfiring
- Thread starter Rogero
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Do you have any idea how many different models of 5hp engines Briggs has built? If you really want us to help you, you must help us. Post the model, type and code numbers for the engine. Yes, we need all three, plus what type of equipment is the engine on.
Sorry, it's my dad's. It's on a Craftsman rototiller, approximately 1990's or 2000's. That's all the info I have.
ChrisBFRPKY
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Is it running when it backfires? Or does the backfire occur when the engine is shut down? Or is it not starting and you have a backfire when cranking the engine?
Fish
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If it is running like that, try to partially close the choke and see if it runs better.
ChrisBFRPKY
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If this is something like a model 130202, sounds like it could be a little lean on the fuel. Check the small stuff first before going all in on what may be a minor issue. I'd turn the fuel adjustment screw counterclockwise about 1/4 of a turn and see how it runs there. Make sure the air cleaner is on it too.
If no improvement, you can move on to checking into a few items, like the flywheel timing key, air gap setting on the coil, spark plug, carb diaphragm, valve lash, and if the valves are seating properly etc.
Usually when one starts to lean out like that, it means there's likely something clogging a carburetor passage or the diaphragm is getting a little stiff with age. A new diaphragm and a few shots of carb spray would be a good idea regardless. That and a quick lapping job on the valves is basic maintenance on the old flat heads.
Through carb or muffler?
Yes with an old inductive timing light firing at the magnets. Just look a the flywheel key, key slot and flywheel. Should be lined up perfectly.
Slomo, please tell me how you use a timing light pointed at the magnets To check timing. How do you start an engine with the shroud off. Do you use an external battery source? Finally, if the timing is off and the key is good, plus air gap is correct, how do you adjust the timing. Asking because at my old age I want to start using my timing light, which I haven’t used on a small engine for over 40 years.