NOTICE:  These are tech pages explaining how I did these mods to my bike.  In almost every case -
I DO NOT SELL THE PARTS DESCRIBED.  I do tell you where I got them.  EXCEPTION - I do sell my custom exhaust mods. 

Tech Tips
Valk Products
My Valkyrie


Electric Fuel Shutoff




      This one is really important. The purpose is to ensure against hydro-lock.  What is "hydro-lock"?
      That's what happens if fuel leaks down into a cylinder while the bike is parked, and you go to start it.  The piston in the filled cylinder tries to compress the air-fuel mixture, but instead it slams into the incompressible fuel.  On the Valkyrie, the starter motor is so strong that it destroys the starter and/or ring gears.  With NO warning, you're walkin and about to shell out a couple thou to fix it.  You have to pull the engine and split the cases which gets spendy.

      "Oh, but no problemo, that's what the vacuum petcock is for, even if I forget to turn it off..."

      Nice try.  That $150 petcock is a P.O.S.  It leaks.  I've replaced mine once under warranty, and cleaned sand out of it several times.  All it needs is a little sand in it, and you have a leak.  It WILL get sand in it - there's no fuel filter, just an inadequate screen tube, and fuel from the pump is notoriously unclean. Have you ever been surprised that you didn't hit reserve yet -  you usually hit it 20 miles ago?  Oh, OK, there it's stumbling, guess I just got some great mileage.  Hey wait a minute - I turned the petcock, how come it's still stumbling?  Oops.  Because you've already used up your reserve, thanks to that leaking P.O.S. The OEM also uses a ball & detent valve - if the ball isn't properly centered on the hole, it's not seated and will pass fuel. So you can also leak if the vacuum failed AND you manually shut it off - but didn't seat it properly. Having the "off" position of the petcock between the "on" and "reserve" makes it imperative to insure you are actually in the "off" position. Most petcocks are different in that the "off" position is fully to the end of the motion of the selector which leaves no room for missing the mark as you can with the stock unit.  

      OK, so now the petcock leaks, doesn't shutoff either manually or by vacuum - now you're depending on ALL SIX carburetor float valves to not leak.  But the sand is already getting through the screen tube and the petcock, guess where it goes next?  All you need is ONE grain of sand to block ONE float needle valve open, and for the engine to stop - one chance in four - with the intake valve for that cylinder open.  (That's a duration of approx 180 out of 720 of the 4-cycle engine's possible states.)  Sounds a bit like Russian Roulette, only with worse odds, but not quite so bad results.

      There are other ways to address this concern.  Some folks replace the petcock with a Pingle.  Not a bad idea - though it's more spendy, and they don't have one that hooks up to the knob so you have to reach under there.  Around $120 or so, if I recall.  Another fix, is to install a fuel filter to keep the sand out.  Well, that's a good idea - but not great.  Only helps if the leakage is caused only by crud in the gas.  Could happen for other reasons too, like worn parts, or failing gaskets.  Some folks do two, even all of these anti-leaking solutions. A bonus benefit of the "belly tank" - if you're not familiar with it, do a search on the VRCC club site - is, fuel is fed to the engine via a fuel pump from the lower tank which is fed by gravity from the OEM tank. When the pump is off, there's no gravity feed passing through it - it acts like a valve. I've never heard any reports of hydrolock happening with a belly tank installed. HOWEVER - I have heard stories of the vacuum diaphram failing in the petcock, and fuel passing through the cracked diaphram, down the vacuum line to #6 and hydrolocking it. Even the Dan-Marc won't stop that scenario. However both the fuel valve diaphram and the vacuum diaphram have to fail for there to be a path for the fuel to pass down the vacuum line - and there is a vent between them, so if the fuel diaphram cracks, fuel will leak out the vent and you will know you have a failure from the leak. If the vacuum diaphram cracks, you will also know it because the bike won't run with the vacuum diaphram remaining closed due to the leak. There is a mod to change the OEM petcock to full manual, and eliminate the vacuum function - and close off the vacuum line. Here's a thread by Gryphon Rider posted on the VRCC board, on that mod: Just do a search over there if the link breaks.  

      Installing a Dan-Marc electric shutoff valve gets the most bang for the buck.  The valve is about $29 online including shipping.  Fuel line and fittings, $10 at most.  And you have a system that will pass gas only when the ignition is on - and there is a vacuum (engine is running) - and the petcock is turned on.  Unless the petcock has failed.  Then the ignition shut-off is your fail-safe backup. Bonus - you can install a switch in a hidden location, say on the handlebar under a lever, and you have an anti-hijack/theft device. 

      Incidentally - This Dan-Marc electric fuel shutoff works so well, I installed one on my Honda Harmony garden tractor too!  The tractor has a fuel shutoff I didn't even know about - didn't read the manual, and it's tucked under the air cleaner.  After a dozen years, the tractor started running really bad. Way rich. Thought the float had sunk, or the float valve stuck open.  The crankcase had 21oz of gas in it - but couldn't find a problem with the float valve. Found the fuel valve is VERY touchy about  it's position. What a PITA. Can't get parts anymore for the H2013 - but did find a carb on ebay. Replaced the carb, and installed a   Dan-Marc and fuel filter. No more problem, and I can STILL neglect to shut the fuel off - it's automatic now!  

      EDIT 05/2017: Found I had a fuel starve problem pulling a heavy camper trailer. Recommend going to the bigger 1/4" orifice valve - P/N as of now 79-AFC1211412. Read more at post on the VRCC board, on that mod: If the link breaks use advanced search for "Belly tank modified" post by MarkT.  


      $29 for the Dan-Marc.   $10 or so for fuel line & fittings. $15 or so if you do the optional stuff.


      An afternoon.  Half the time is spent pulling the tank and the airbox.


    • 1/4" orifice Dan-Marc Valve from Just google if the link breaks.
    • a couple feet of 3/8" (I think) fuel line.  Take your fuel line with you to match it up.
    • I replaced those spring hose clamps with 8 screw hose clamps
    • Inline fuse holder
    • toggle switch (optional), or
    • standard 4 or 5 pin relay, momentary-on pushbutton sw, small diode, and LED ("step" LED fixture is nice) (optional)
    • several feet of multistrand 18ga wire (optional)
    • wire ties

    Tools I used

    • Screwdriver
    • hose cutter
    • soldering equipment including shrink tube
    • Long needlenose pliers
    • 1/4" drive metric socket set


      Drain the tank using a siphon hose.  Remove the tank and airbox.  Remember to unscrew the knob, there's a phillips screw inside the knob hole.  You also have to pull off the main fuel line and the vacuum line (other side).  Front and back screw (10mm & 12mm hex heads) and it comes off.

      Check the picture above.  I added fuel line to the left and right sides of the T fitting so I could move the fuel line T fitting forward to allow the Dan-Marc to sit ahead of the crossmember.  This is to make it easier to reconnect the fuel line at the petcock - provides some flex movement.  Found this out the hard way. Don't worry about those glass tubes below in the pic - it's neon for my night lights, which I decided wasn't such a good idea - potential sparks from high voltage in this location, maybe not so good.

      Connect the two wires on the Dan-Marc:  one of them to a ground - solder on a ring connector and secure it with a screw to ground.  The other wire - connect to the accessory circuit (Lg/R), or to the running lights circuit Bl/Br).  It doesn't matter which is hot & which is ground. Put an on/off toggle switch in this line (or the ground line) and hide it, if you want to have a hidden fuel shutoff.  Or install a relay as a "latch" - so if you kill the engine by the kill switch, the fuel shuts off and won't turn back on unless a hidden switch is cycled. I powered mine from the kill switch output wire (Bl/W wire on the 9-pin Bl mini connector in the headlight - same wire at Bl/W to the coils, also at Bl/W at Pin4 of the ICM) via a relay set up as a latch (connect relay output to relay trigger using a diode so you can use a low-power pushbutton sw - it's output will power the trigger only, not the relay output load as well.) Installed a hidden LED indicating power on, and hid a momentary-on pushbutton that activates the latch. Here's a link to a discussion thread on this install - complete with a latch-relay wiring diagram - thanks to BonS. Scroll most of the way down to BonS's diagram:,41361.0.html Now if I kill the engine with either the key or kill sw, the pushbutton has to be pressed to turn the fuel back on. Yeah I know it works - took me a while to get in the habit of always hitting the button after starting, and when I forget, it always sputters in about a mile!

      This is also a good time to desmog if you haven't done that already.  While you have the air box off.  I did it now, anyway.  Here's a link to some good instructions:


      It's automatic.  Enables fuel flow when the ignition is on.  Now you can stop worrying about hydrolock.


All technical mods described here are merely reports of what I've done.  You may attempt to replicate them at your own discretion and risk if you choose.  Horseapple Ranch, LLC and Mark Tobias will in no way be responsible for the results of your attempting to perform these mods on any motorcycle, regardless of the outcome.

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