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Weird carb overflow issue?


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RaceFan

 
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Weird carb overflow issue?

Mon Jul 13, 2009 7:26 am » Post: #1 » Download Post

My bike stood for about 3 weeks while I waited for some track time.
The day before I was going to go out I get a strong smell of fuel in my garage, when I move the bike to get ready to load up Fuel pours out the belly pan, I check and it is completely filled up with fuel. Pour it all out clean the bike up and then load. I don't see any leaks from the overflow pipes at all. Next morning I check and the belly pan is full of fuel again. Same deal, clean up and head to the track.

Bike refuses to turn over, fuel has filled the lower cylinder and is causing an hydraulic lock. Strip the fairings off and take plugs out, rotate the motor and tip the bike backward for good measure. A stream of fuel came out of the exhaust pipe, it was just about full.

My fuel tap does not close 100%, it has a slow drip.
The only things I can think of are the needle and seat in the carb? But surely that would run out the overflow not fill the lower cylinder?

Took the carbs off last night and the right(problem) carb's float height was slightly out. Adjusted it and did't smell any fuel in the garage this morning. Will see later.

Has anyone seen anything like this? First for me.
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fontyyy

 
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Mon Jul 13, 2009 7:28 am » Post: #2 » Download Post

Nope, stuck or badly adjusted floats will fill the cylinder.
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RaceFan

 
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Mon Jul 13, 2009 7:32 am » Post: #3 » Download Post

fontyyy wrote:Nope, stuck or badly adjusted floats will fill the cylinder.


Thanks. The only mystery is why it fills after being fine for 3 weeks prior. Only difference was that the night time temps dropped into the negatives.
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Dave Ett
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Mon Jul 13, 2009 9:44 am » Post: #4 » Download Post

Things shrink when they're cold.
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StephenRC45
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Mon Jul 13, 2009 10:06 am » Post: #5 » Download Post

As most of us have found out hey Dave?
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jimmy13
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Mon Jul 13, 2009 10:49 am » Post: #6 » Download Post

I had virtually the same problem, is there any rust in the tank?

I had a dodgy fuel tap so check that its actually off when its turned to off. Main thing I had to change was the needle valves although they may look okay the most tiny amount of wear can render them useless. My tank was full of rust which had made its way into the carbs and furred up the needle valves wearing them down....replacements and a repaired tap and I was no longer using my expansion chambers as fuel tanks lol

Just some pointers from my experience.
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RaceFan

 
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Mon Jul 13, 2009 11:06 am » Post: #7 » Download Post

No rust in the tanks, old one did but I replaced it with a spotless unit.
The needles look fine, but if my chanbers are full this evening when I get home then I know to replace them.
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ricey3

 
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Mon Jul 13, 2009 11:25 am » Post: #8 » Download Post

it happens, best thing you can do is when you know your leaving it for a while is make sure the fuel taps off and drain the bowls.
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RaceFan

 
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Wed Jul 15, 2009 7:55 am » Post: #9 » Download Post

Corrected float height seems to have sorted the issue out.
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Dave Ett
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Wed Jul 15, 2009 8:56 am » Post: #10 » Download Post

Cool, and thanks for posting the result - next searcher may find this thread helpful. Wink
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