Briggs missing

[SHB]

Have a Briggs 10.5Hp industrial- commercial engine on a brush mower. Name plate shows it to be a model 28B707, type 1130-E1, code 980518ZA, believe the manual refers to it as a L-hea . Engine has a miss, runs ok at full power, rough when throttled back, dies when idled. So far I have disassembled and cleaned the carburetor (no change) and changed the plug (No change). What should I do next? Is the coil dying?

 

[Rivets]

When you cleaned the carb did you remove the main nozzle and make sure all the jets were open? That main nozzle supplies fuel to the idle circuit and can contain as many as eight jets.

 

[bertsmobile1]

A common problem with Sv engines is errosion of the exhaust port
This means the exhaust never completely closes
In the early stages the engine runs fine when the throttle butterfly is wide open but dies when the engine slows down .
SO start with the easy bit and double check you have cleaned the carb properly and that the float is set correctly as per the instructions on outdoor power info .
Then if no joy pull the head off ( thus you will need a new head gasket before you start ) and check that when the engine is at TDC on the firing stroke both valves are closed .

 

[SHB]

When you cleaned the carb did you remove the main nozzle and make sure all the jets were open? That main nozzle supplies fuel to the idle circuit and can contain as many as eight jets.

Thanks! I’m not sure that was done, so sounds like a good starting point.

 

[SHB]

A common problem with Sv engines is errosion of the exhaust port
This means the exhaust never completely closes
In the early stages the engine runs fine when the throttle butterfly is wide open but dies when the engine slows down .
SO start with the easy bit and double check you have cleaned the carb properly and that the float is set correctly as per the instructions on outdoor power info .
Then if no joy pull the head off ( thus you will need a new head gasket before you start ) and check that when the engine is at TDC on the firing stroke both valves are closed .

Thanks! Will revisit the carb. Does the exhaust port erosion mean the end of this engine? This problem showed up after it had sat for a while.

 

[bertsmobile1]

No
You recut the seat & shorten the valve stem
PIA job to do but it is a once every 10 to 20 years so not so bad .

 

[StarTech]

Note: To remove the main nozzle use a straight side hollow ground flat tip bit. Also note some nozzle are bond in so tight it is nearly impossible to remove them without damaging them so be careful.