Author Topic: Petcock Questions  (Read 224 times)

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Offline andyfield

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Petcock Questions
« on: February 06, 2018, 02:28:52 pm »
Hi guys,

I'm learning about this bike as fast as I can.  There is a LOT of information about petcocks out here, and it's tough to filter through.  I'm cleaning the rust out of my tank as we speak, and replacing the petcock today.  However, I'm doing this on the advice of others, and my knowledge that rust is bad wherever it shows up -- not on my own mechanical merits.   

Other than that, I really don't know what the petcock does, or what I'm supposed to do with it. 

So two questions:

1)  What settings does it need to be on, and when?  I'm assuming it goes on RUN when it's running.
2) What exactly does the thing do?  Explain it like I'm four years old, please. 

Thanks guys!

Andy
1984 Honda Shadow
2003 Kawasaki Vulcan
2004 BMW R1150-RTP
1990 Kawasaki Concours

Offline Mettler1

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Re: Petcock Questions
« Reply #1 on: February 06, 2018, 02:51:25 pm »
  Replace mine several yrs ago. I leave it on run as vacuum line opens it when you crank the engine. Comes with a built in filter. Shuts of fuel when you stop the engine.
https://www.murphskits.com/product_info.php?cPath=1_107&products_id=140
   

   Don't know if you know about hydrolock but watch video.   https://www.youtube.com/watch?v=4W6k3pTdAXw&feature=plcp
 
   I also run a NAPA 3006 90 degree fuel filter that I install in the fuel line just above the carbs. Saves getting a possible kink when you bend  the fuel line.
https://www.napaonline.com/en/p/FIL3006
           
 
« Last Edit: February 06, 2018, 10:52:00 pm by Mettler1 »
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Offline Stasch

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Re: Petcock Questions
« Reply #2 on: February 06, 2018, 03:01:02 pm »
These are vacuum operated petcocks that have 3 settings.  'RUN', 'RES' and 'PRI' (There is no 'OFF')

When working as it should (See hydrolock reference in previous post) fuel flows by gravity when set to 'RUN' or 'RES' and only when there is vacuum, which only occurs while engine is running. 

If engine is not running, then 'RUN' or 'RES' are essentially 'OFF'.

'RUN' is the normal setting to leave it at whether running or sitting, unless you have gone to RESERVE.

'PRI' lets fuel flow freely with no vacuum required.  You should NOT leave it on this setting.  (See hydrolock reference in previous post). 

Only use 'PRI' to prime carb bowls if the bike has been sitting a while or installing carbs after maintenance and bowls are dry.

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He IS a racer, hence the forward lean!!  by: Mettler1

Offline Mettler1

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Re: Petcock Questions
« Reply #3 on: February 06, 2018, 03:15:04 pm »
  Nice to see you are still vertical !! :beerchug:   Winter sucks in Mich. but my C10 is nice and waiting for spring. Have a good day!! :great:
'94 Concours 115,000 miles-- 7th gear,2MM,KB fork brace,Over flowtubes,Stick coils,Tcro shifter,GPS,SiSF'sTorque cams,SPOOKFAK,block off plates, SS brake & clutch lines,KB risers, FENDA EXTENDA, emulators, SiSF carb Spa, Delkevic exhaust, Murphs' knee savers +grips, etc

Offline andyfield

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Re: Petcock Questions
« Reply #4 on: February 06, 2018, 04:53:57 pm »
Thanks for all the help, gents.  So let me display my ignorance once more:  Why is there a RES setting?  When I feel myself running out of gas, do I switch over to that?  Are there two tanks?  Why didn't they just make it so you keep it on Run the whole time?
1984 Honda Shadow
2003 Kawasaki Vulcan
2004 BMW R1150-RTP
1990 Kawasaki Concours

Offline connieklr

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Re: Petcock Questions
« Reply #5 on: February 06, 2018, 05:02:15 pm »
To clarify those three positions:

PRI (Prime): Petcock lever handle in the forward position.
RUN (Run): Petcock lever handle in down position.
RES (Reserve): Petcock lever handle in the rear most position.
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Offline Bob_C_CT

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Re: Petcock Questions
« Reply #6 on: February 06, 2018, 07:28:00 pm »
By turning the lever to reserve it opens an opening further down in the petcock that allows access to more fuel in the bottom of the tank, around a gallon and a half, @50 miles, IIRC.

The reserve is for two types of people 1) don't keep track of fuel left until it starts sputtering. 2) others that are trying to get more miles in on a long trip before having to stop to re-fuel (and have larger bladders than me haha or wear depends hahaha).

Every Spring I empty my tank in the car and truck but if you don't keep your tank clean you may be opening yourself to tank debris in the bottom of the tank when switching to reserve.

By the way even after reserve runs out you can tilt the bike to the left (petcock side) and get more useful gas.
In other words you never can empty the tank through the petcock.


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Offline who me?

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Re: Petcock Questions
« Reply #7 on: February 06, 2018, 07:51:50 pm »
The petcock has 2 tubes for fuel to go into The longer/taller one is the main(Run) the shorter one is the res/prime IIRC It gives you about a gallon or so of fuel after the fuel level gets below the intake of the longer tube They are inside the filter of the petcock in the tank
I have no idea about anything.
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