Mikuni on an R80 help

Discussion in 'Airheads' started by hardwaregrrl, Sep 6, 2012.

  1. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Hey all. Wondering if any one has base line jet settings for a 32 TM mikuni on an R80 St. Also if you have cable info that would be great too!! Tia
    #1
  2. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    They are flat sides. Not going above 6,000 ft
    #2
  3. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Anybody?
    #3
  4. ontic

    ontic

    Joined:
    Jul 14, 2008
    Oddometer:
    1,317
    Location:
    Melbourne
    Sorry mate,
    If it was a VM34, I would have sent you a PM.

    What's the story? Do you have these carbs already?
    #4
  5. Kai Ju

    Kai Ju Long timer

    Joined:
    Jul 29, 2009
    Oddometer:
    2,196
    Location:
    Long Beach, California
    If they were VM's we could get you in the ballpark. No idea on the TM's
    What did they come off of ?
    Were they meant for an airhead ?
    What jetting do they have right now ?

    Come to think of it, I had a TM 38 on my Rotax powered Ninja 250 and it uses essentially the same brass that the VM series does.

    So here goes:
    These are the specs for VM38s on a '77 R100/7


    Description Spec
    Main Jet 210
    Pilot Jet 25
    Needle Jet 166 P-8
    Jet Needle 6DH3
    Slide Cut Away 2 This will likely be different since the TM is a flatslide
    Main Air Jet 0.5
    Needle Valve Ass'y 3.3

    The other option is to call SUDCO and see if they have specs for what you got.
    I made my own cables from the stock cables, take your time, measure three times before you cut anything.
    #5
  6. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Thanks! This at least gets me started.....the carbs are brand new. I'm sanding a floor for Nathan Mende of Boxerworks-service and he ordered these for me from parts unlimited in a bit of trade. I was assuming I'd have to make my own cables by grinding the barrel down on the existing cable. I know they're jetted very rich. out of the box..250 main 45 pilot. Needle jet 389 Q-2 jet needle 5FP17. Thanks for the help, I'm racing it again next weekend and am dumb enough to want these carbs on the bike for the rally.

    #6
  7. ontic

    ontic

    Joined:
    Jul 14, 2008
    Oddometer:
    1,317
    Location:
    Melbourne
    Next weekend! Sounds like you've got a busy week:D

    I got a couple of these cable kits from Venhill, one for my throttle and one for my choke (because I have changed both the throttle and the choke and about to do the carbs)
    http://www.venhill.co.uk/Cables_-_C..._UNIVERSAL_THROTTLE_CABLE_WITH_SPILITTER.html

    I don't have my mikunis yet, but these kits look like they'll do the job very well. 48mm stroke in the splitter- a bit light and plasticy compared to the bmw splitters, but I suppose it will work just fine.
    Aside from all your jetting stuff, you may need to look into the stroke needs of your carbs and what your bmw splitter and throttle can actually provide. Airhead Wrangler helped me out pointing this out with a post of his somewhere a while back.
    No point upgrading to mikunis if you can't open right em up:D
    #7
  8. Kai Ju

    Kai Ju Long timer

    Joined:
    Jul 29, 2009
    Oddometer:
    2,196
    Location:
    Long Beach, California
    ..........for right now at least.
    A week is not a lot of time to make cables and get carbs dialed in.
    Also, depending on what throttle you are planning on using, you may have to modify the gear mechanism to get it to open the slide carbs all the way. The stock setup on mine only gave me about 3/4 throttle. If need be I'll take a pic or two on how I modified mine to give you some idea.
    Also, the exposed wire length will be too short to fit the slide so grinding the barrel won't be enough, you'll have to shorten the outer cable to effectively lengthen the inner cable.
    Sorry, got to leave for work but pm me if you got questions about cables and such.
    #8
  9. supershaft

    supershaft because I can

    Joined:
    Sep 9, 2010
    Oddometer:
    9,116
    Location:
    San Francisco Bay area
    They are brand new? Send then back and get bigger ones!
    #9
  10. Beater

    Beater The Bavarian Butcher

    Joined:
    Sep 3, 2009
    Oddometer:
    3,701
    Location:
    Atlanta, GA, USA
    On an R80? The little research I've done here seem to me that the 32 or 34 were the sweet spot for an R80 ... and the 32 provided more low end grunt ... which is what she is going for ...

    Am I wrong?
    #10
  11. Sniper X

    Sniper X De Oppresso Liber

    Joined:
    Jul 18, 2006
    Oddometer:
    33,474
    Location:
    Central New Mexico, 7420ft above sea level
    Definitely if she won't be venturing above 6000ft and needs more air. I had 40s on my R100RS and up here at 7500ft that was great but I would have done 38s if I had still lived in Monterey at sea level for sure.
    #11
  12. Sniper X

    Sniper X De Oppresso Liber

    Joined:
    Jul 18, 2006
    Oddometer:
    33,474
    Location:
    Central New Mexico, 7420ft above sea level
    BTW I want a set for my R80RT so when you do get a good idea of a baseline, let me know and I can calculate with i need to do up here at my altitude.
    #12
  13. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    So I know it's a bad idea to be slapping these things on and racing a rally.....but I want to play with my new toy!!:D Hardest part was figuring out the cables. No one has cables for the R80 2-1.....weird. Anyway, I wandered into the back of Cycle Word in Athens GA and found some 4 wheeler cables that are going to work. Had to put a barrel on the end of the carb to get the appropriate free play, but the slides open all the way!! Yippie!!! Going to buy a bunch of jets tomorrow and try to get it dialed in....I know it's a fucking stupid idea.....but if I get it running right and it pulls, by golly whats the problem with racing it !? I'll post up some pics of the install and let you know where I land with jetting... I went with 32s because I don't want bigger I want a bit quicker acceleration, that's it.

    @ontic: nice kit, Hans! I just got lucky.....hoping to post up what they are off of so anyone else doing this doesnt have to dig.

    @Kai Ju: I just can't stand having a new set of mikunis sitting there.....call me crazy.:loco

    And Dean and Nathan did all the brainiac work.
    #13
  14. supershaft

    supershaft because I can

    Joined:
    Sep 9, 2010
    Oddometer:
    9,116
    Location:
    San Francisco Bay area

    More low end grunt than 32mm Bings? That could be done with 38mm Mikuni's. I would run 36's for a lot more low end and a lot more high end at the same time but that's just me. Stepping away from Bings you can have it all at once. It's easy to do when you start from such a low performer. :D
    #14
  15. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Welp.....the bike runs very nicely. I just got them on, hooked up and cables loosely adjusted. Didn't feel like taking a ride in the dark with these new guys. Here's a few pics of the cable mod.....had to turn the carbs in a bit more as the cable top was interfering with the HPN tank.

    [​IMG]

    [​IMG]

    Here's the original cable assembly I stole the cables from.

    [​IMG]

    And the other end.

    [​IMG]

    And a quick video....please turn you volume down as I don't want you to get pissed at me for being loud.:D

    <a href="http://s814.photobucket.com/albums/zz66/hardwaregrrl/?action=view&amp;current=4D868670-F1F1-4EB9-937E-75E201626DC3-4882-0000073C8C4C5D1A.mp4" target="_blank"><img src="http://i814.photobucket.com/albums/zz66/hardwaregrrl/th_4D868670-F1F1-4EB9-937E-75E201626DC3-4882-0000073C8C4C5D1A.jpg" border="0" alt="Uploaded from the Photobucket iPhone App" style="width: 160px;"></a>
    #15
  16. R-dubb

    R-dubb Dubbious Adventurer

    Joined:
    Aug 4, 2001
    Oddometer:
    5,309
    Location:
    San Francisco
    So, how did it work out? :ear
    #16
  17. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Not so hot, still working out the bugs....Having trouble jetting it, but it may be because I've never done this before.:evil Pilot was a 45, major stumbling from closed throttle to 1/4 turn, dry fouled plug......luckily Beater had a few pilot and main jets for me to try. I went to a 35, then a 20! Seems the 20 is the ticket....then it stumbled and fouled from 1/4 turn to half.....the needle has 5 positions and it was in the middle....so I've dropped the needle all the way to the end.....that's the way Beaters carbs for his old R80 were. Haven't gotten to run it flat out to swap the mains. Hopefully tomorrow I can get close, and if no cigar, I'll put the bings back on and scratch my head.
    #17
  18. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Well, it is a definite improvement. Much crisper and quicker throttle response....and then it keeps on giving!!! Got the pilot circuit sorted yesterday, and the needle position, rode the bike this morning and it felt great! A bit of stumbling at the top and then I went through about 6 main jet sizes before I nailed it! Carb came with 35 pilot, 250 main, and the middle of five positions on the needle. It is now a 20 pilot, 175 main, and leanest position on the needle....a bit difficult for me to sync. Can't use the twinmax, and I will not use the shorting method. Nathan dialed the sync in, bike runs great. Hopefully I get a bit better fuel mileage, but it will get a real shakedown this weekend as I will be racing the bike at Black River Stages as a stand-in for the Airhead Rallye Team!!!!:evil Jason will be down under at the Australian Safari Rally. Wish me luck!:freaky
    #18
  19. mark1305

    mark1305 Old Enough To Know Better

    Joined:
    Feb 7, 2005
    Oddometer:
    6,318
    Location:
    Merritt Island, FL
    Good luck, Jenna!
    #19
  20. hardwaregrrl

    hardwaregrrl ignore list

    Joined:
    Jan 26, 2006
    Oddometer:
    8,171
    Location:
    Atlanta
    Thanks Mark.:thumb !!!
    #20