20HP Twin Cylinder occasional rough running

[jtm3885]

OK
Last year,I posted a thread concerning my troubles with a 20HP B&G engine. SOMETIMES, it would run great and SOMETIMES it would not. So far, I have removed gas tank and checked for foreign material, replaced fuel lines, replaced fuel filter, replaced fuel pump, poured over two cans of carb cleaner into carb and gas, pulled fuel selonoid and cut off plunger. The problem is still occasional and getting very aggravating. Because is is occasional, it is hard to troubleshoot cause.
I can sometimes keep engine running by pulling the chock on. Acts like fuel starvation.
Please help. I have not been able to find any one else with this issue.

 

[mechanic mark]

Troubleshooting Poor Engine Performance | Mower & Small Engine Repair | Briggs & Stratton FAQ

 

[Tom Armstrong]

OK
Last year,I posted a thread concerning my troubles with a 20HP B&G engine. SOMETIMES, it would run great and SOMETIMES it would not. So far, I have removed gas tank and checked for foreign material, replaced fuel lines, replaced fuel filter, replaced fuel pump, poured over two cans of carb cleaner into carb and gas, pulled fuel selonoid and cut off plunger. The problem is still occasional and getting very aggravating. Because is is occasional, it is hard to troubleshoot cause.
I can sometimes keep engine running by pulling the chock on. Acts like fuel starvation.
Please help. I have not been able to find any one else with this issue.

You did sensible work that COULD be the cause for similar problems in some engines. I went through all that too, as well as clearing a plug in the gas cap vent. In addition, you should check and set the intake and exhaust valve clearances. This is not likely the problem though.

SOLUTION TO MY Briggs and Stratton Model 406777 type 0115 E1 running rough under load when warm was BADLY out of specification ignition coil gaps. They generated enough spark to run OK when cold, but when warmed up, the voltage dropped and was then insufficient for proper firing. I reset the gaps to specification for my engine and the engine is running properly. If this does not do it for you, you could have one or two (my engine has one for each cylinder)faulty ignition coils.

 

[mechanic mark]

You did sensible work that COULD be the cause for similar problems in some engines. I went through all that too, as well as clearing a plug in the gas cap vent. In addition, you should check and set the intake and exhaust valve clearances. This is not likely the problem though.

SOLUTION TO MY Briggs and Stratton Model 406777 type 0115 E1 running rough under load when warm was BADLY out of specification ignition coil gaps. They generated enough spark to run OK when cold, but when warmed up, the voltage dropped and was then insufficient for proper firing. I reset the gaps to specification for my engine and the engine is running properly. If this does not do it for you, you could have one or two (my engine has one for each cylinder)faulty ignition coils.

Good news, thanks for responding and sharing information.