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Old 03-11-2012, 12:47 PM   #1
Canadian FJR OP
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DR-350 Fuel overflow ??

Took my sons 1999 DR-350 out of winter storage yesterday and went for a little ride. All seemed well but returned to the garage today and gas was all over the floor. Pulled the plug and the cylinder was full. Checked the oil level and it was fine. Not a hint of gas in the oil. Seems like both the fuel petcock diaphram AND the float stuck. After getting things all dried up and sorted out I just fired it up and went for a little longer ride. The bike is running as good as always but this little problem has me concerned. Is anyone able to post a good pic of the carb assembly. I want to see how the overflow is routed. Thanks in advance.






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Old 03-11-2012, 02:32 PM   #2
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I just found this information. Why would the float & needle not stop the fuel from flowing even if the the petcock flapper was bad?

"Stock vacuum petcocks available on dual sport models (DR350S and DR350SE) are known to degrade and fail after several years. Vacuum petcocks have three positions: ON, RES, and PRI. The positions are described below:
  • ON - fuel flows only when the engine is running determined by vacuum present at the carburetor
  • RES - reserve fuel similar to ON
  • PRI - fuel flows regardless of engine state, used to initially fill (prime) the carburetor bowl if the bike has been sitting for several days
Vacuum petcocks contain a thin diaphragm that allows fuel to flow in the ON position when the engine is running. After several years, the diaphragm degrades allowing gas to leak past the diaphragm, flow down the vacuum line, and enter the carburetor. The excess fuel causes an abnormally rich air fuel mixture. An excessively rich mixture will result in poor fuel economy, poor idle, weak performance, bogging, or the engine may not run at all. It can also allow large amounts of fuel to leak into the crank case over long periods of time. Gas in the crankcase dilutes the engine oil which can lead to serious engine damage.
A common solution is to replace the vacuum petcock with a simple ON/OFF petcock from a dirt only model (DR350) or a Yamaha Raptor 660 model number 5LP-24500-01-00 ON/OFF petcock. The Raptor petcock (labeled fuelcock on Raptor parts fiche) appears to be used from model years 2001 through 2005.
If an ON-OFF petcock is used, it is critical to seal off the unused vacuum port on a CV carburetor. The engine will not run with the vacuum port open. Auto parts stores sell inexpensive vacuum caps for this purpose although any solution that seals the port completely will work. "

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Old 03-11-2012, 08:15 PM   #3
dtp
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Common issue... your vacuum petcock went bad. Get a replacement like the Yamaha Raptor one you can find here and other places (like your local dealer)...

http://procycle.us/bikepages/dr350.html

Only $25!
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Old 03-12-2012, 08:28 AM   #4
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Thanks for the reply. Replacement shut-off it is.







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Old 03-13-2012, 06:17 PM   #5
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I went with an in-line "ON/OFF" fuel valve with the stock petcock still in place. I have not been able to get the stock unit to leak again but I thought that the addition of the second fuel valve was an added bit of security. I also drained and replaced the engine oil just to be on the safe side.

I'm still curious as to why the float does not stop the flow. There are many bike out there with a manual petcock that never have a problem and rely on just the float to prevent overflow. Any thoughts or comments?



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Old 03-13-2012, 06:29 PM   #6
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I dunno... maybe having the gas sit there in the carb causes deposits that prevent the float from shutting off the flow or blocking the overflow outlet?

Sounds like your "secondary petcock" should do the trick.
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