This is what I figured, but in a motorcycle group, someone was told
that if the petcock wasn't closed, gas would go through the carb and
get into the oil when the engine wasn't running. Why wouldn't the
float valve be as good in a motorcycle as in a car or lawnmower?
It is. However , the float valve is a simple thing that is
a hair or piece of dust causing a slight leak.... In older motorcycles,
like a Honda 160, cleaning the float valve was trivial. It is more
complicated now, I think , because the carbs have a lot more pieces...
That being said, if the valve leaks JUST A LITTLE, the fix was to
always turn off the stopcock under the fuel tank. That gets to be a
after it floods the engine the first time. And a good habit.....
So, you need to get the float valve cleaned out, and then get into
the habit of closing the stopcock in preparation for the time in the
future when you go to start the engine and it is flooded. The problem
doesn't usually happen when the engine is running because the
fuel consumption is greater than the leak....
Andy in Eureka, Texas
It would, however in a car the gas is pumped from below so once the
pressure is gone, no leak.
A lawn mower is gravity feed (except those with a diaphragm pump built
in), but usually just barely, the tank is seldom much above the carb. I
motorcycle is the perfect storm; with the tank well above the carb and
fairly large fuel lines.
OK. Makes sense. Thanks to you and andy.
The Honda CB450 that I posted about a few times in the summer and fall
is running now, but not reliably or too well. I need to work on the
throttle, which is hard to control. But it looks like it won't be
until the spring. That's ok. It's too cold to ride anyhow.
I haven't had the problem with leaking gas afaik.
I've never flooded a motorcycle engine with gas for two reasons:
shutoffs were easy to check and use, and carburetors were designed with
floatbowl overflow tubes.
A neighbor ended up with the crankcase on his tiller full of gas because
the shutoff was hidden and easy to forget. Another had it happen to his
riding mower because there was no shutoff. I had a push mower whose
tank would drain if left a few days. I never found gas in the oil but
assumed the float valve didn't quite seal. There was no fuel shutoff,
so I tried not to pour in more gas than I intended to use that day.
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