Briggs and Stratton 125cc hot running

[oil pan 4]

Had a newish briggs 300 series 125cc mower i fixed today. The usual, had no oil on the dip stick, gas was terrible.
Dumped the gas and water out of the tank and carb, put in a splash of fresh gas mowed some grass, tied off the safety shut off let it run for a bit, mowed some more grass. Finally ran out of gas before I did.
The only thing I like about these 125cc mowers is they run for a while on a cup of gas. Easily mow a small yard with 8oz of gas. If its overgrown, forgetaboutit. They got no power.
Wasn't burning any oil, so it earned fresh oil. Figured I'd throw my torpedo thermometer in there after running for 30 minutes while 95 outside.
It hit 240f as 240 is the max temperature on my thermometer, probably would have gone a bit higher, impressive.
Dumped what was probably the original oil plus that reclaim oil, blew out air passages with compressed air, didn't really see anything go flying so it wasn't blocked. Put some lucas 10w-40 bike oil I had taken as payment for another mower job. Definitely overkill. It will love its owner long time.
I usually don't see mowers go much over 210f on the oil.

 

[andyd]

Running lean will run hotter

 

[fantastic]

89 or higher octane.. I've just been using 91 E0 for OPE.

 

[grasscutter]

Most Briggs & Stratton engines have a little scooper on the crank end of the connecting rod for scooping up oil.

The connecting rod bolts literally go through the scooper on their way through the connecting rod cap.

If that oil is too thick, it won't splash. Oil not splashing could lead to an overheat condition. That's what I'm thinking.

I suggest 10W-30.

 

[Lawnman23]

Most Briggs & Stratton engines have a little scooper on the crank end of the connecting rod for scooping up oil.

The connecting rod bolts literally go through the scooper on their way through the connecting rod cap.

If that oil is too thick, it won't splash. Oil not splashing could lead to an overheat condition. That's what I'm thinking.

I suggest 10W-30.

Not for vertical shaft engines like this. There is an oil slinger wheel that runs off the cam that bolts to the bottom cover. It basically sits in the oil.

What your thinking of is for horizontal shaft engines.

 

[grasscutter]

What your thinking of is for horizontal shaft engines.

You are most correct about that sir.

 

[jake wells]

Ethanol free gas and SAE 30.

 

[oil pan 4]

Most Briggs & Stratton engines have a little scooper on the crank end of the connecting rod for scooping up oil.

The connecting rod bolts literally go through the scooper on their way through the connecting rod cap.

If that oil is too thick, it won't splash. Oil not splashing could lead to an overheat condition. That's what I'm thinking.

I suggest 10W-30.

If it was running 100c like a typical one I'd run 30wt, probably straight 30wt.
The old oil was likely 9 to 10 cSt at 100c.
40wt lucas oil should be like 14 to 15cSt at 100c, it tends to test on the thicker end of the 40wt scale.
But this mower isn't operating at 100c, its doing more like 115 to 120c. I pulled my thermometer at 240f to prevent damage, was likely going to settle a bit higher.
That 40wt ought to about 10cSt at 240f.
So its not any thicher when warmed up than 30wt oil in a typical mower that runs a bit cooler.
Virtually all 30wt oils would be around 8cSt at 240f, thats a bit thin.
It has to be over a thousand cSt to not splash.