Toro mower with B-S motor, poor hot start

[rfsmith48]

Folks,
We have a Toro 22" mower with electric start. The mower is about 6 years old. It has a new battery.
Over that past several months it has been difficult to start when the motor is hot.
Spark is good.
Which leads me to believe that the carb/auto choke is going south.
Has anyone seen this? How did you fix it?
Thx
Rog

 

[nbpt100]

Remove the air filter and see where the choke plate is when the engine is off but hot. It should be fully open. When cold it should be fully closed.

 

[rfsmith48]

Thanks!
I will check that next.
Rog

 

[sgkent]

how old is the air filter? I had a friend whose air filter used to get damp from where it was stored. Would run like a champ for about 10 minutes then hard to restart. Never asked to work on it so I didn't. About 10 years later I had one doing the same thing, took a look at the air filter and it was damp. Replaced it, and it ran fine. Bought a new shed and put it on a concrete pad. Quite dry in there, no more damp air filters.

 

[rfsmith48]

Guys,
Thanks for the responses. The air cleaner is in good shape.
The auto choke plate IS closing when the motor is hot and off. (And the mower won't start.) I blocked the choke plate open when it misbehaved in the garage, and it started right up!
What is the appropriate service or parts to fix this?
Thanks again.
Rog

 

[Rivets]

You need to post the units model and serial numbers so we know which engine you have. Better yet would be to post the model, type and code numbers for the Briggs.

 

[rfsmith48]

Mower S/N 315032336
Motor: 128M05-0026-F1 (Flathead motor)

 

[mechanizm]

Folks,
We have a Toro 22" mower with electric start. The mower is about 6 years old. It has a new battery.
Over that past several months it has been difficult to start when the motor is hot.
Spark is good.
Which leads me to believe that the carb/auto choke is going south.
Has anyone seen this? How did you fix it?
Thx
Rog

first thing, see if it starts up with a squirt of starting fluid. that means it's running lean. I've had lots of mowers that did this. on one, i drilled-out the main jet a tad and now it's fine. EPA forces manufacturers to lean-out the carbs... People then throw away perfectly good mowers and buy new ones. How much pollution is caused to make a lawn mower from scratch? A LOT....

 

[nbpt100]

Guys,
Thanks for the responses. The air cleaner is in good shape.
The auto choke plate IS closing when the motor is hot and off. (And the mower won't start.) I blocked the choke plate open when it misbehaved in the garage, and it started right up!
What is the appropriate service or parts to fix this?
Thanks again.
Rog

That is a problem if the choke is closed with the engine hot and off. It should be open. You likely need a new thermostat. THERMOSTAT BS-593208.

Make sure the arm that opens the choke is moving freely and not getting hung up on anything. The spring should smoothly return it to close the choke plate. Unless the thermostat lever moves (when hot) and prevents it from closing. Ref the exploded diagram below. Good Luck.

https://www.partswarehouse.com/128M05-0026-F1-Briggs-and-Stratton-Engine-s/205366.htm