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


1325watt Compufire Alternator




      Want lotsa electrical toys?  How about heated clothes?  High power audio?  Heated grips, high power lights, unlimited running lights, compressors...  Want to use them at once? Then you NEED this mod. 

      If you look over the mods listed below this one on the Tech Tips page, and total the power use of my toys, you'll see that I'm well over the capacity of the stock 546watt alternator.  So I had to use them selectively, and you could see the effect in the dimming of the lights at night.  If you exceed the capacity of your alternator, the deficit is made up by the battery.  Until it's drained.  Then you're walkin. Assuming you didn't already burn out the alternator.  Walkin again.

      There's a couple other aftermarket alternators available.  One is from Simpro which was blasted by WW and others for misrepresenting a used product as new.  My take is,  they are the used car salesmen of the motorcycle aftermarket.  I didn't look much at the third one after I found the Compufire which was clearly superior.

      The Compufire is a NEW alternator - not rebuilt.  Got a great review from WW. It's based on an automotive alternator with custom cases made to fit the GL1500.  That is, the Gold Wing GL1500.  You can't install it past the Valkyrie frame unless you move the engine, though it does bolt up to the engine and plug in, once you solve the frame issue.  Enter this article.

      Let me say here that some folks are leery of doing frame alterations.   I received unsolicited criticism for doing this from non-engineers who are unqualified to advise an engineer on engineering matters.  However, I am the Master of My Domain, IOW (with apologies to Seinfeld) I own my outcomes and I am responsible if I screw something up.  I am also an engineer, though not a mechanical one, I have sufficient training and experience to do a little digging and determine whether this mod in my opinion will weaken my frame.  Obviously, I concluded it won't/didn't.  If you don't want to cut your frame, don't do this mod the way I did.  The alternator can be installed by moving the engine.

      The other consideration in deciding to do this, is do I want to be on the road 2,000 miles from home with an alternator that can't be replaced without pulling the engine?  I can just hear the stealer now: "bend over pal."  Ain't gonna happen. 

      This puppy puts out 60amps at 14.8v, 50% more than the stocker's max,  AT IDLE!  Zowie!  I'm gonna install a laser for blasting errant cages!


      The Compufire is listed at $429 on their web site.  No doubt it can be found cheaper - I did through my commercial account with one of my suppliers.  That's basically the main cost.  There are always small incidental costs to these projects, twenty bucks or less.  You also need to replace the battery with the bigger Yuasa AGM battery sized for the Gold Wing.  It's available with the alternator as a kit from Compufire.


      Take a weekend and enjoy yourself.  After all, it's quality time with your baby.


    • some spray paint that matches your frame. I used Rustoleum Gloss Black
    • electrical tape
    • wire ties (I used several repositioning some other wires)


    • metric socket set
    • metric combo wrenches
    • metric allen wrenches
    • torque wrench
    • phillips and standard screwdrivers
    • measuring device like a dial caliper
    • masking tape, fine tip marker
    • air body saw or hacksaw
    • die grinder with carbide burr or Dremel
    • 4 1/2" angle grinder with 1/8" cutting wheels
    • flat bastard file
    • hammer and chisel
    • bike lift
    • Dremel with plastic cutting saw blade and rotary file


      Remove the cover over the stock alternator.  Remove the side cover over the radiator reservoir.  Remove the cover mount bracket and the alternator mount bolts.  The stock alternator is a tight fit to remove, but the Compufire is quite a bit bigger.

      Disconnect the battery terminals.  The manual says  remove the two connectors on the alternator now but it's easier to take it out first.  Back the alternator out, then turn the shaft end outwards to remove it.  BTW, the red wire and fixture is a blue LED cluster that lit the inside of the Kuryakyn tranny cover.



      The Compufire is 0.1" longer, and 0.975" greater in diameter.



      On the Compufire, the impellor IS the nut on the end of the shaft, which has a 8mm allen socket.  Removing the impellor gains you nothing as the overall length remains the same, and then you have to try to tighten it with a torque wrench while holding the drive unit in the tight confines of the install site.  I shortened the electrical output post a bit, but it wasn't any help.

      Check the clearance needed by positioning the alternator in the install path.

      I decided to cut the side of the case first to get the max clearance I could there, then take what I had to out of the frame.  Mark a window slightly taller than the width of two of the drive fins in an "X" configuration, while ensuring you don't cut into the seat for the forward lip of the alternator.  This serves as an alternate location for the O-ring which prevents the Valk from doing Harley impressions.  pay attention that the alternator won't be hitting the vertical frame tube above the plate that holds the swingarm pivot.

      Seal off the hole with a rag before cutting to keep filings out of the gears & oil.  I used an air body saw to make the short cuts while being sure I stopped before the new O ring seat.


      I used the 4 1/2" grinder with cutter blade to score the other cut.  I know, wrong tool for cutting aluminum but the right size and shape.  I cut through the sidewall in the middle then took advantage of the brittleness of the aluminum and knocked the piece out with a hammer and chisel.



      I used the diegrinder to smooth out the cut and bevel the edges.  Be careful, that cutter goes through aluminum like butter.  The finished cut:


      Rechecking the clearance with the Compufire, looks like I need to cut at least where the angle changes on the metal just forward of the swingarm pivot.

      I cut it using the 4 1/2" grinder, busted it the last little bit, then dressed out the surfaces and edges of the cut with the die grinder.


      Of course you want to paint it.  I used gloss black Rustoleum, 2 coats.


      OK, now do a test fit.  Have you cut it enough?


      Not a millimeter too much, or too little!  Pretty good for a field hand...

      After you've proven it will pass through the gap, position the driver impellor in an "X" config (put the tranny in 5th and bump the back wheel) and install the rubber drive cushions.  Insert the new O ring off the alternator as shown, and put the old O ring where the new one was.


      Carefully pass the alternator into position, turn the driven impellors on the alternator in the "+" position  and seat it home while ensuring the new O ring is seated in the gap without protruding.  Torque the mount bolts to 22 ft-lbs.


      The regulator wire will plug in without modification though the latch won't work.  I wrapped it with electrical tape to seal and secure it.


      You'll need to cut a small piece out of the plastic side cover.  I cut that with a 1/16" X 2 1/2" cutter wheel in the die grinder.  Here's the pieces I cut out:


      Replace the stock battery with the Gold Wing size battery.  You'll need to modify the battery tray as it needs to run fore-aft rather than crosswise.


      Finished!  I might come up with some chrome to cover it, but while it's clean, for now, I like it running cool out in the air.


      Put the meter on it - it puts out 14.8 volts even at idle.  Took her for a spin after dark.  Turned on 350 watts of headlights, all the LEDs, 250 watts of audio and flipped on the compressor.  Noted the road was lit up much brighter than I've ever seen it before, and there was no dimming of the lights when I added to the load.  Noticed it smelled hot for the first 40 miles or so, when I stopped.  It stopped the new, hot smell while I was running errands the next day.

    More Info Added 6/06: 

      I should have added above,  that this alternator puts out too much power for the stock Valkyrie battery.  In fact, Compufire makes it available as a kit with a Gold Wing Yuasa AGM battery.  Get the kit.  The Compufire alternator will ruin the stock battery.  You will need to modify the battery tray to hold the bigger battery.  I used a Dremel and cut the partitions so the battery runs fore-aft rather than sideways.  And my amp for the sound system runs the same way, alongside it.




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.

All content on copyright 1999-2006 Mark Tobias except "Riders Say", "Dyno Day", Vallejo and Shop Manual and Alternator Review pages, and SWF and MP-3 files and their graphic icons, and any content specifically attributed to another author.  
All rights reserved.