Toro Lawn Mower stalling after 10 minutes of mowing, then unable to start for a while. Some smoke.

[Briggs Mowerman]

I'm looking after someone's yard for a few months, and am using their mower.
It's a self-propelled Toro 22" with a Briggs and Stratton motor.

The grass is thick and grows fast. Needing to mow weekly.
After about 10 minutes of mowing, the mower seems to lose power and stalls in any thicker patches.
Then it's very hard to start.
The first time it stalled, I tried 30 times to start it, with no luck.

However, after letting it cool for an hour, it starts no problem.

Also, I noticed some smoke coming from up around the engine bay after it stalled.
Also some puffs of smoke are coming from the exhaust on a restart.
I heard a tinkling sound, like the metal was very hot, so I'm guessing it's overheating.

Oil level is fine and the oil is clear and clean.

I noticed the blades were not very sharp, and cut grass tips are ragged.
So I wonder if blade sharpening might help.

I stopped using the catcher, as grass seemed to be bunching up, and this has helped to some extent.
I also stopped using the self-propelled feature, as the engine is struggling just to cut the grass.

I'm not a mechanic, so if you have any advice, please explain in laymans terms.

 

[bertsmobile1]

1) sharpen or replace the blade
2) adjust the valve lash ( see You tube videos )
3) remove the engine cover & clean the fins on the engine
IF this does not make it 100% better come back for more information

 

[Briggs Mowerman]

1) sharpen or replace the blade
2) adjust the valve lash ( see You tube videos )
3) remove the engine cover & clean the fins on the engine
IF this does not make it 100% better come back for more information

Thanks Bert.
What do you think is causing the stalling/smoke/overheating?

The only youtube video I found on adjusting valve lashes is this one:

As it has no commentary, I'm in the dark as to what problem is being fixed.
As I'm not a mechanic, I suspect it's not something I should attempt, as I could make things worse.

 

[Briggs Mowerman]

I'm going to have to speak to the owner before attempting to fix anything.
I just want to have some understanding of what the most likely problem is, and what needs to be done.

 

[Briggs Mowerman]

The engine cooling fins are visible without removing anything and they are very clean already.

 

[bertsmobile1]

Overheating without surging is either timing slightly out or a build up of dirt around the cooling fins.
When oil gets too hot it gets too thin so the oil rings can not scrape the oil off the cylindrer oil.
SMOKE tells us nothing without the colour of the smoke

 

[Briggs Mowerman]

Overheating without surging is either timing slightly out or a build up of dirt around the cooling fins.
When oil gets too hot it gets too thin so the oil rings can not scrape the oil off the cylindrer oil.
SMOKE tells us nothing without the colour of the smoke

Thanks Bert. That is helpful.
The smoke is only present when it is at max temperature and has stalled from overheating.
I thought it was steam at first, but looking closer, it was more dense than steam, and a light grey.

If I uploaded a video of it running, could you hear a timing issue from the sound of the motor running?

 

[bertsmobile1]

If the heads got really hot then the valve guides may have shifted in the head .
Check by visual inspection
Inlet & exhausts are identical so sit the same height off the floor of the head