HRM 21 SV engine going?

dgl24087

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I have a very old HRM 21 SV that has been a great mower, I bought it used a few years ago and have been more than happy with it. Today while mowing, the engine coughed and blew out a big puff of white smoke, then had a burnt oil smell for a few minutes. The engine settled down and ran perfectly while I finished the lawn. After finishing, I reduced the engine speed and let it idle for a few minutes then shut it off. I checked the oil level and upon removing the oil cap, oil gushed out of the engine, and had a slight gasoline odor. I change the oil every year and use Honda 10w-30 oil. My lawn is practically level with a very small area (about 10x10) that is about 30 degrees slope. Thoughts?
 

jp1961

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Hello,

Is the engine an OHV design or a valves in block engine? It's possible the head gasket blew.

FWIW, a two cycle mower (or a 4 cycle that has pressure oil lubrication) is your best option for cutting a lawn that has a slope to it.

I believe the Kawasaki lawnmower engine had an oil pressure system.

Regards

Jeff
 

primerbulb120

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I have a very old HRM 21 SV that has been a great mower, I bought it used a few years ago and have been more than happy with it. Today while mowing, the engine coughed and blew out a big puff of white smoke, then had a burnt oil smell for a few minutes. The engine settled down and ran perfectly while I finished the lawn. After finishing, I reduced the engine speed and let it idle for a few minutes then shut it off. I checked the oil level and upon removing the oil cap, oil gushed out of the engine, and had a slight gasoline odor. I change the oil every year and use Honda 10w-30 oil. My lawn is practically level with a very small area (about 10x10) that is about 30 degrees slope. Thoughts?

The root cause of your problem is likely a sticking float valve, which filled your crankcase with gas.
 

dgl24087

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Update: The mower is running fine, no issues.
 

cpurvis

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A two-cycle engine lawnmower IS just the ticket for mowing steep slopes. Unfortunately, our wonderful EPA has effectively eliminated that option. I'm not aware of any new lawnmower with a two-cycle engine now. I'm still running my 32 year old Toro with Suzuki two stroke engine and would buy a new one in a heartbeat, if only they were still available.

Back to the OP's Honda: I would definitely change the oil if you smelled gas in the crankcase. You may also want to install a shut-off valve in the fuel line to prevent it from happening again.
 
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