Hydraulic lock up

[marcmax]

Let me start by saying I always, always shut off the fuel petcock when I park my R65 and always use the center stand if it will be parked for more than 30 minutes or so.

Last night I was a little distracted when I got home and obviously forgot to turn off the petcock. When I went into the garage this morning the smell of gasoline was overpowering and I knew I had forgotten to turn it off. Under the right cylinder was a small puddle, about 1/4 cup of fuel.

Later when I rolled it out into the driveway and attempted to start it. The engine made maybe a 1/4 turn then just stopped. I tried again and no movement at all. I had been installing a new taillight and turn indicators and my first thought was I had missed something and had an electrical issue. Out came the meter and everything checked out fine.

Then I remembered the puddle of fuel and thought that can't be. Pulled the plug on the right cylinder and it was soaking wet. Grounded the plug on the opposite side of the engine for safety and hit the starter. It looked like a whale had just surfaced and a plume of gasoline shot 3 feet in the air and immediately the bike started running on just the left cylinder.

I immediately shut it down and reinstalled the plug. I then started to worry about fuel in the oil. Checked and the oil level was right as it should be with no indication of gasoline. I changed it anyway. Tried it again and it fired right up and just sat there idling contently.

Do I need to be concerned about any damage in that cylinder?

[Bob_Roller]

This should not be an issue for you, I had the same thing happen a few years ago, even with independent floats .

I did the same thing you did, removed the plugs took the bike out into the street, operated the starter until no fuel came out .

Engine started up with no problems .

No fuel in my oil, I took it out for a 2 hour ride just to be sure, oil level didn't change .

I had just changed the oil the week before and didn't feel like changing it again !!!

[montmil]

Was the tank full? Only thought I have is that the fuel's head pressure forced the gas past the float needle and up into the carb's throat.

Good news is that the engine stopped after a minimal rotation. Liquids don't compress very well.

[Tony Smith]

Do I need to be concerned about any damage in that cylinder?

Given that they swallow valves without bending crank or rod I'd say a resounding "No".

If the oil level didn't change I would have been inclined to have left it in, but oil is cheap I suppose. I used to find it terrifying, but the approved start method for most aircraft engines in cold climates is to pump a dose of avgas into the oil to thin it up. First time I saw that I thought is was the most bizarre thing I'd ever heard of,but when you think about it, a thin film of circulating oil will do a far better job of lubricating than thick oil that will not circulate, and as the oil heats up the fuel will boil off. I reckon you could have left it.

[nhmaf]

You may be OK in that you got lucky and the other cylinder didn't fire and try to compress the incompressible fluid - that will bend connecting rods, etc.  With just the starter pushing, it didn't get shoved hard enough to bend anything, but it the other cylinder had been at the right spot to get combustion, you'd be a sad person, I think.

Time to get a lottery ticket - you're in a good run!

[Luca]

but it the other cylinder had been at the right spot to get combustion, you'd be a sad person, I think.
 

The cylinders approach TDC at the same time.  If one cylinder has gone hydraulic it is on the compression stroke and won't be getting power from the other cylinder on the exhaust stroke.

[nhmaf]

Correct - I had forgotten about the boxer sequence.  On some inline-4s, I've seen the engine start to fire, with more drastic consequences.