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Discussion Starter #1
Hi All,

I bought my 2009 Ninja 500 last week (this is my first motorcycle) and took it for a ride yesterday. I brought it back to the storage late in the afternoon, but later in the evening I realized that I forgot to shut the petcock off. Unfortunately the storage was already closed, so I had to wait till the morning.

Now I'm a bit scared - the owner's manual says that it's OK to leave it open, however I see many petcock issues over the internet; looks like vacuum petcocks are prone to fail, fuel can leak into the carburetors, flooding the engine - so I'd like to get some general advice.

How likely would this happen, and what should I look for? What are the symptoms? What should I check before I try to crank the engine over next time?

Thank you!
 

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Relax. Check the oil level before you ride it again. If an appreciable amount of gas makes it through a defective petcock, then leaks through the carb needles and seats, then floods the cylinders, and then runs past the rings to the crankcase, the oil level will rise noticeably. The probability of that sequence happening is very low, although not impossible.

Always checking the oil before riding is a good habit to develop anyway. If the oil level is unchanged, and the bike starts and runs normally, then you laid awake in a cold sweat all night for nothing. I've got another model Kawasaki that also has a vacuum petcock and the petcock on that bike doesn't even have an off position, only run, reserve, and prime. That indicates how worried the Kawasaki engineers were about the issue.
 

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The vast majority of those who encounter that particular issue of both the petcock failing AND the float valves failing to seal all have one thing in common: neglect. It is extremely rare, though not impossible, for that to happen to a well maintained and often ridden motorcycle. I have 147,000 miles on my EX, 127,000 of that put on in the last 10 years, and have never had it happen to me. I've only rebuilt the petcock once and never put the selector to OFF unless I'm removing the tank. I've rebuilt the carbs 3 times at this point too, each time installing new float valves.
There's several others which have come through my garage and while I've seen leaking petcock diaphragms (which is more common), none have filled the combustion chambers or crank case with fuel. I have seen it happen to a friend's Ninja 250 but it did a lot of sitting and the rubber had dried out plus the fuel varnished, which comes down to neglect. It was long past due for a carb rebuild and could have benefited from a fuel tank inspection.

The fuel system on these bikes is often neglected as they're everyone's starter bike and not worth much. If you really want to sleep easy and have a proper running motorcycle, I'd recommend pulling the petcock and either replacing all the rubber (trust me, go OEM here) or replace the whole petcock (again, go OEM), check the fuel tank for any crud floating around which could potentially prevent proper seating of the float valves and petcock and clean and rebuild the carbs.
 

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Discussion Starter #4
Thanks for the replies; I will check the oil level and open up the oil fill port to take a sniff of what's inside.
The bike was in really good shape and the tank was shiny clean inside when I bought it (also ran well + stable idle) so I'm somewhat optimistic.

Wow, 147,000 miles on a bike is quite unheard of, It's good to know that even a small bike like the Ninja can last that long.
 

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I can tell you apparent previous car has nothing to do with the possibility of leaking. When I bought mine with 35k and meticulous care with receipts it still had gas in the oil. I replaced the petcock, rebuilt the carb, and no problems since. I don't shut off the valve.
 
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