Honda XLV750 into RS750 Flat Tracker build

Discussion in 'Some Assembly Required' started by ktmmitch, Feb 15, 2021.

  1. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    It has always been something on my bucket list to build a special flat tracker to ride here in the UK, and due to Covid lockdown, I've spent quite some time gathering together the pieces needed to build a replica Honda RS750 flat-tracker, as raced successfully in the USA in the 80's.
    First off was to source an early air-cooled XLV750 motor and wiring loom, which I did from XLV750 enthusiast Johan, in Portugal.
    I have also had a set of 19" x 2,50 & 19"x3,50 alloy wheel blanks delivered from MSI, South Gate, California. These will be cnc machined to the old spoke pattern in our workshop.
    The frame is to be fabricated by a good friend, Geoff, who runs Co-Built in the UK, they are well-known for flat track and custom frame work, and we are mainly working from archive photographs.
    We managed to source, from Mac McGrew in the USA, who himself builds & races an RS750, a complete billet rear linkage he made for his own bike, so that is a major piece of machining saved.
    We will make our own custom shock to suit the linkage, as well as custom triples to hold some conventional period forks.
    The main engine problems are 3-fold. The original Honda guys had to change the gearbox output shaft from bevel gear to splined to accept a conventional sprocket, as the XLV7550's were shaft drive, plus the output shaft turns in the wrong direction for the chain drive conversion, so they changed the primary drive from gear to duplex chain, which corrected this.
    Then, as the original XLV750 motor has both carbs between the vee of the engine, we need to switch the rear cylinder so that the carb is on the right, using the exhaust port, and then the inlet becomes the exhaust, so that both headers exit on the left. This will mean reversing the camshaft lobes to reverse the rear cylinder firing order.
    Here's a few pictures to let anyone interested know what I'm up to.

    Attached Files:

    #1
  2. r60man

    r60man Long timer

    Joined:
    Mar 14, 2013
    Oddometer:
    2,760
    Location:
    Centralish PA
    Ummmm, yes please!
    #2
  3. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
  4. Franque

    Franque Nilé na sohakélwa manga

    Joined:
    Apr 26, 2015
    Oddometer:
    807
    Location:
    Marseille, France -> Dakar, Sénégal
    Watching this, this sounds really cool! I never realized it that the RS750 was based on an XLV. I thought I had heard that the motor was CX - based.
    #4
  5. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    IMG_2946.JPG IMG_2962.JPG IMG_2961.JPG The first Honda vee twin flat tracker was based on the CX500 motor
    #5
  6. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
  7. Wildebeest90210

    Wildebeest90210 Long timer Supporter

    Joined:
    May 24, 2013
    Oddometer:
    5,694
    This is an idea I've considered before, love the look and the history behind this Honda. Some nice technical challenges as well, very much looking forward to this. I've worked with Geoff for some years now, a legend as you know. He did the frame on my Kenny Roberts Banshee thing, weighs nothing and strong as...
    I'm local to Geoff so if I could help in any way, I have access to cheap 5 axis CNC amongst other things.
    :lurk

    IMG_2553.JPG
    #7
    pennswoodsed, Yella DR, AK650 and 5 others like this.
  8. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    7,802
    Location:
    New Zealand
    I'd hate to see an XLV750 chopped up, even to make an RS copy...but if it's just an engine, go for it ! I had an XLV750 engine under the bench for years, always wondered what I could put it into. I loved my XLV750, the motor was fantastic, the frame looked like it was made from some 50mm box section...and off road it was like riding with 2 bags of cement on your lap. But shit, I loved thrashing that thing. Hondas 022.jpg tools 013.jpg
    #8
  9. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    Geoff's a great guy, can't wait to get into the frame build with him. Send me a message with your 5 axis details for future reference, we have 3 & 4 axis cnc here.
    150784877_255488636061242_6887725931126217457_n.jpg 151215467_3756240707763604_3637537682169825730_n.jpg
    #9
    Dutch idiot, JagLite, AK650 and 3 others like this.
  10. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    Big day tomorrow, the XLV750 is in the frame jig, ready to have its new, replica tube work wrapped around it by Geoff Cain of Co-Built fame.

    IMG_3132.jpg
    #10
    JagLite, AK650, Brtp4 and 12 others like this.
  11. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk

    Attached Files:

    #11
  12. sruss67

    sruss67 Been here awhile Supporter

    Joined:
    Aug 2, 2009
    Oddometer:
    408
    Location:
    Devonport, Tasmania, Australia
    That is a very impressive bit of machining there.
    #12
  13. Pezz_gs

    Pezz_gs Cant ride for crap

    Joined:
    Nov 13, 2004
    Oddometer:
    5,587
    Location:
    Sydney Skunkworks
    Enjoying this Mitch!! :lurk

    One question if I may . . . . :hmmmmm

    With the chain drive conversion, is there a kit available?
    #13
  14. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    Not that simple, the output shaft turns the wrong way for a chain sprocket, so I'm having to reverse the direction by changing the clutch/crankshaft connection from gear primary to duplex chain.....
    #14
  15. Pezz_gs

    Pezz_gs Cant ride for crap

    Joined:
    Nov 13, 2004
    Oddometer:
    5,587
    Location:
    Sydney Skunkworks
    Oh wow..... going to need a whole lot more popcorn
    #15
  16. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    7,802
    Location:
    New Zealand
    So what did they do to the RS to change the rotation of the output shaft ?
    #16
  17. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    the output shaft turns the wrong way for a chain sprocket, so they had to reverse the direction by changing the clutch/crankshaft connection from gear primary to duplex chain.....
    #17
    villageidiot and AK650 like this.
  18. motu

    motu Loose Pre Unit

    Joined:
    Dec 28, 2001
    Oddometer:
    7,802
    Location:
    New Zealand
    And so back to the old question - was the XVL the production version of the RS...or was the RS the race version of the XLV ?
    #18
  19. Wildebeest90210

    Wildebeest90210 Long timer Supporter

    Joined:
    May 24, 2013
    Oddometer:
    5,694
    An update courtesy of Geoff's Insta story and some snipping....
    Not sure of the term when you update some ones thread for them with theft by social media...:hmmmmm

    2.PNG 1.PNG
    #19
  20. ktmmitch

    ktmmitch Long timer

    Joined:
    Sep 29, 2009
    Oddometer:
    1,781
    Location:
    uk
    NOT SURE, BUT THE MORE INTEREST, THE BETTER
    #20
    AK650 and Wildebeest90210 like this.