Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

[JasonT]

I started this season with empty fuel tank and carb. Put in new gas, new oil, new filters ( oil,fuel, air ). Runs very rough, with occasional billow of white smoke. Replaced oil with oil / reslone mix, new fuel again with Lucas cleaner mix, new plug. Still running very rough with billowing white smoke from exhaust ( no noticeable oil in exhaust ). I am at a loss? Any ideas? Stuck valve? Any comments appreciated. I have searched the forum, but have found nothing this specific. Thanks,Jason

 

[cambre]

Re: Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

I started this season with empty fuel tank and carb. Put in new gas, new oil, new filters ( oil,fuel, air ). Runs very rough, with occasional billow of white smoke. Replaced oil with oil / reslone mix, new fuel again with Lucas cleaner mix, new plug. Still running very rough with billowing white smoke from exhaust ( no noticeable oil in exhaust ). I am at a loss? Any ideas? Stuck valve? Any comments appreciated. I have searched the forum, but have found nothing this specific. Thanks,Jason

See if spark plug has any carbon on it and check gap. Check fuel filter, may be stopping up. Check engine air breather, should be around air filter. Smoke could be from to much oil in crank case. If you leaned engine over to far oil will get to valves and on top of cylinder. It will burn off. Oil may be to thin. Head gasket may be leaking. If you can get to head bolts tighten them. I don't think you have stuck valves as it wouldn't run at all. Carb. float may be stuck after sitting for the winter. Could be stuck rings but I kind of doubt it. I take it is one cylinder engine. If two cylinder it may be running on one. You would probably know this. Hope this helps. Cambre

 

[pugaltitude]

Re: Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

Does the oil smell of petrol?

If so then the needle in carb is not sealing and allowing fuel into cylinder.

Do you have excess oil in air filter?

If so then possible blown head gasket.

 

[JasonT]

Re: Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

Thanks for the advise. I will check the oil for fuel smell. No oil in the air filter. Runs very rough, and when starting, it turns over like something is bent ( best I can describe it ). Like hard / then easy / hard then / easy,then fires? Again. thank you for all inputs.......

 

[mechanic mark]

Re: Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

Results engine manual & parts list, replace spark plugs with B&S plugs & gap to specs., correct plug listed in manuals, check oil level, use oil listed in manual, adjust valves to specs.

How to Repair Small Engine Problems: Briggs & Stratton FAQ do not panic, take your time reading & troubleshooting step by step, process of elimination.

 

[bertsmobile1]

Re: Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

Thanks for the advise. I will check the oil for fuel smell. No oil in the air filter. Runs very rough, and when starting, it turns over like something is bent ( best I can describe it ). Like hard / then easy / hard then / easy,then fires? Again. thank you for all inputs.......

Hard-easy-hard-easy says a stuck valve or a bent valve or too much valve clearances .
White smoke says duff oil seal on inlet valve or blown head gasket ( other more exotics but these are the most common )

 

[JasonT]

Re: Bronco 42 in. mower with a Briggs & Stratton31P777-0293-E2 engine running rough

Thank you to all that have replied. Awesome advise. Sorry for the late response, been down with medical issues. Hopefully I can try these suggestions this weekend. Will re-post when accomplished. Thanks again to all for the help...Jason