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Old November 20th, 2020, 10:43 PM   #1
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Name: Austin
Location: Vancouver Island, BC
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Motorcycle(s): 2001 ZZR250

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Smile 2001 Ninja 250 Running Bad with Petcock On, Runs Fine Off

I am posting to tell people my fix, so if someone has a similar issue, they might benefit.

Although it took me over a week to finally figure out (working on it an hour or two per day). Granted it's my first time working on a carb. I was so close to just bringing it to the mechanic, and ready to hear that my engine was shot.

I just got a 2001 Ninja 250 w/ 46'000km, my first bike, for $600. I knew the petcock was leaking down into the crankcase, so I changed the oil, replaced the petcock, cleaned the carb and adjusted the valves.

So get everything back together, I sync the carbs, runs perfectly fine. Then I put on the gas tank, and it runs like crap, RPMs all over the place. Hanging really high, then dropping really low.

Originally I thought this was a vacuum leak, or perhaps I adjusted the valves wrong. Or maybe I forgot to put back something on the carbs.

I was pretty sure it was running rich. A lot of smoke out of the tailpipe. But no matter how I adjusted the mix, it didn't run any better. And once it was warmed up, it just wouldn't start at all (possibly also due to an improper mix screw at this point).

Then I looked down at the bottom of the carb, and gas was just pouring out! Open up the float bowl, and it's obvious that one of the float needles was sticking in a semi-open position. The wire of the float needle was a different style than the original.

So I bent it up to be more like the original one, and worked perfectly fine ever since.
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Old November 21st, 2020, 05:30 AM   #2
Triple Jim
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Motorcycle(s): Ninja 250

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That makes sense. If a leaking petcock caused fuel to get into your oil, you also had a leaking float valve. It takes both to have fuel going places it doesn't belong.
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Old November 21st, 2020, 09:33 AM   #3
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Name: AKA JacRyann
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Motorcycle(s): CB125T, Ninja250R racer,Ninja250R street EX250F#1 EX250F#2 EX250E CBR250R(MC19) CBR250RR(MC22) VF500F CBR600RR

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hey, good job on finding issue. Float valves and height are critical for proper operation.
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