Thread: Drz400 Thread
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Old 12-11-2012, 06:38 PM   #17222
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Joined: Jul 2012
Location: Morris Plains, NJ
Oddometer: 102
I agree with the above idea. Even though i needed to install new valves and basically do an entire top end rebuild after having my petcock leak and fill the case. i still like the vac operated petcock.

I think some people in here mis-understand the reason for using the raptor petcock. It is so you can shut the fuel off manually every time you stop the bike.

The stock petcock actually does shut off when its not running. Its done through a vacuum line from the carb that activates a diaphragm. This is nice for when you take a spill because the float in the carb stays open when a bike is on its side, and when the bike shuts off it will cut fuel flow so that you dont spill gas out the overflow.

The reason for the raptor petcock is to protect yourself from when multiple things happen:
-The diaphragm in the stock petcock gets worn and doesnt do its job
-the o-ring in the carb is old/cracked/flattened
-the overflow on the carb is clogged or not working.

Those 3 things go wrong and you hydro-lock. The raptor petcock is so you manually shut the fuel down instead of relying on the diaphragm, eliminating the first thing in the line of events. BUT Leave the raptor petcock in the on position and you basically just made it so 2 things need to fail instead of 3, a worse situation.

Sorry to write a book and take everyone to school, but i really want everyone to understand the reasoning behind the use of the raptor petcock so we can avoid the hydro-lock issue all together. Basically if you do the raptor petcock, remember to shut off your fuel every time you stop and park.

that being said... my set up is: Stock petcock, Inline fuel filter, Inline shutoff valve. The shutoff valve being my backup to the diaphragm in the petcock.
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