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As I was looking for info on how to drain oil from my lawnmower (reference this post), I came across a video that discussed hydrolocking, which is something I'd never heard of. I've seen other posts in this forum that suggest symptoms point to hydrolocking, but I've seen no information on how to prevent it. The Youtube video linked below apparently shows how to prevent this by ensuring the piston is at top dead center on the compression stroke so that the valves are closed, thus preventing oil from getting into the piston chamber. Thoughts?

Or

Drain the oil and fuel if you want to tip it over. Only talking about 18 ounces of oil and fuel. So much easier restarting once you are done say sharpening the blade or oil changes. Doesn't foul the plug out either.

Probably needs an oil change and fresh fuel anyway.

Not sure how that answered my question. The oil change was the point of tipping the mower. The fuel tank is nearly empty. I plan on running it to empty before changing the oil. I just want to know whether the video I linked correctly identifies how to prevent hydrolocking.

The main way to prevent hydrolock is don't store and tip the engine with the spark plug facing down. Any other direction for prevent oil hydrolock. But there is also fuel hydrolock when the gas drains from the carb and fills the cylinder. The little bit of fuel that runs out of the carb into the intake when the engine is tipped with the carb up won't cause a hydrolock.

Now there is a case of some of the older briggs engines had the valve cover and breather on the muffler side of the engine. When the engine is tipped muffler side down that breather can fill full of oil. and then when the engine is tipped back level the oil can run from the breather across the vent tube into the carb and cause some serious smoke. And on rare occasion can hydrolock the engine.

So, does pulling the rope til it tightens indicate that the valves are closed, preventing fuel and/or oil from leaking into the piston chamber and out to the muffler and/or air filter?

Hello Dan400man,

Depends on the mower design you have.

The idea is to not get the oil into the breather and prevent getting oil into the engine cylinder.

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Drain the oil and fuel if you want to tip it over. Only talking about 18 ounces of oil and

Auto Doc's said:

Hello Dan400man,

Depends on the mower design you have.

The idea is to not get the oil into the breather and prevent getting oil into the engine cylinder.

Click to expand...

Hence draining the oil and fuel.

I'd be sucking out even if i had to modify my grease gun .

Not all oil comes out but draining is certainly a step in the right direction.

To eliminate doubts, remove the spark plug and crank it over a few times to purge any liquid that could possibly be trapped in the combustion chamber.

Then put the plug back in after servicing and start it up. It may smoke for a couple of minutes, but that will clear itself once running.