Airhead Mikuni Owners Thread

Discussion in 'Airheads' started by Uncle Pollo, Oct 2, 2012.

  1. Uncle Pollo

    Uncle Pollo Long timer

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    Since I am installing mikunis on my r80 (why god why? :p ), I believe it would be useful to the poor souls out there to have an idea what type of jetting are we running on our machines.

    I was thinking on a format like my signature, so the next poor bastard that tries to figure out his carburetors will have a baseline in which where to start.

    Altitude matters ... so if you may ... show off your carb type and jetting!

    We could compile them here on the first post for reference ... :augie
    #1
  2. hardwaregrrl

    hardwaregrrl ignore list

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    Hey, I've got TM32's on my R80. Still working on jetting. I am running a 155 main right now (might be a touch lean), pilot is a 20 but I've got to work on the pilot circuit as she is cold natured. needle jet is a series 389 Q-2, and jet needle is an FP17, air jet is a 2.5. needle is at the leanest positon. Bike runs well, still is a hard start, air screw is 1 1/2 turns.
    #2
  3. Uncle Pollo

    Uncle Pollo Long timer

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    Cmon .... if you google mikuni airhead this is the second hit!
    #3
  4. ontic

    ontic

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    I've got vm34's on their way to me now, jetted to some specs that were provided to me for my particular engine set-up. I won't bother trying to publicly provide any specs until I can actually test them, they might run like dogs!


    :lurk
    #4
  5. hardwaregrrl

    hardwaregrrl ignore list

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    Well, currently I have 165 mains, 25 pilot air screw 2 turns out, needle jet is P2, and 5FP17 jet needle. Bike still is cold natured at cold starts, but runs like a top.
    #5
  6. Kai Ju

    Kai Ju Long timer

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    For this to be useful, posters need to add Model/Year/level of modifications such as exhaust and intake/airbox. Cylinder head work, cam, compression etc.

    So here goes:

    1977 R100/7 with stock replica mufflers ( EMGO), '79 starter cover with the cast aluminum intake opening, stock clamshell airbox with stock paper filter and the stock elbows going into the bellmouth of the carbs and sealed. Stock engine with 42,000 miles and 150 lbs compression.

    VM38

    Main Jet 210
    Pilot Jet 30
    Airscrew 1 2/3 turns from seated
    Needle Jet 166 P-8
    Jet Needle 6DH3
    Slide Cut Away 2
    Main Air Jet 0.5
    Needle Valve Ass'y 3.3

    I started with a 200 Main Jet but power would increase when I backed the throttle off some. May go to 220 to see what happens.
    Pilot jet was a 17.5 which was recommended by a friend of a friend. Totally inadequate, engine wouldn't run/idle unless the airscrew was seated all the way. Worked my way up to 25s and was pretty happy except slow to warm up. Went to 30s a couple of days ago. No change in warm up but off idle transition at speed,i.e accelerating from steady state throttle, feels better.
    In mixed riding I used to get 35 mpg with the Bings, now I get right at 40 mpg. The engine pulls really clean through the rev range and, if I use common sense, giving it a handful results in clean acceleration. No hole to climb out of, just acceleration.
    #6
  7. DeutschMark

    DeutschMark Full Tilt Boogie

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    I'll play. Engine is a follows in my 89 R100RS:

    9.4:1, 44mm intake valves, dual-plugged heads, Scheffer asymmetrical camshaft, timing at 28 degrees BTDC at max advance, two large snorkels on the airbox, baffle in the mufflers punched out (for a slightly better sound more than anything else).

    Mikuni VM34 carburetors
    6DH4 Needle
    2.5 Slide
    195 Mains
    PO (159) Needle Jet
    35 Pilot Jet

    I edited this to reflect the change to 195 mains from 170's. I picked up 4 mph on the top end.
    #7
  8. Beater

    Beater The Bavarian Butcher

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    I have VM32's on the Dobber (a '85 R100 G/Sified). I will post what works for it ... but as of right now, the carbs are WAY out. They came off a '76 R75.

    This thread can be a great 'tuning' thread ... or at least some great places to 'start'.
    #8
  9. Uncle Pollo

    Uncle Pollo Long timer

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    Post the settings anyhow. It may one day help someone
    #9
  10. oldroadie

    oldroadie Two wheel addict

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    Location:
    North Alabama mountains
    1972 R75/5, stock air box, K&N filter, two into one exhaust with SuperTrapp end cap:
    Mikuni VM32, 200 main, 30 pilot, 6DH3 needle clip in middle, P-0 needle jet, 1 1/2 turns out
    1000 ft above sea level.
    Still too fat but very smooth. More jets coming right up....

    Update: Exhaust changed to baffled pipe, Supertrapp is shelved for now. Mains 190, pilot 30; both feel too rich and the plugs are dark chocolate brown. 180s and 170s along with 25 pilots on order. I'm guessing 25 pilots and 170 mains is going to be the order of the day.
    #10
  11. Uncle Pollo

    Uncle Pollo Long timer

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    Update: ran fine 2 up to sandia mountain. 10000 feet. Id pulls well over 5k rpms after 9k feet altitude. Idle was a little low at 10.5 k feet altitude but it made it!

    That is my butt dyno.
    #11
  12. dvblue_2000

    dvblue_2000 Probationary

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    I made the Mikuni conversion on an R60/7. I got the kit from Rocky Point and they were jetted way too rich for 5300 feet. I eventually put in the leaner jets provided and lowered my slide needle a couple notches and now it runs great, but I remember getting better gas mileage than 37-40 mpg on the R60/6 I used to have. The plugs look pretty good, and I'm not going to monkey with it anymore. One thing that gave me fits is that the choke plungers weren't going all the way back down when I lifted the choke levers so it would run real rich, wouldn't idle, and dribble gas out the carbs (so I fiddled with the floats). Once I figured this out it tuned up nicely. Every time i lift the choke levers I also push the plungers down with my finger. I also gave them a little shot of WD40.
    #12
  13. Uncle Pollo

    Uncle Pollo Long timer

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    You here too?
    #13
  14. Uncle Pollo

    Uncle Pollo Long timer

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    I am going to swap my main from 140 to 135 and see.
    #14
  15. dvblue_2000

    dvblue_2000 Probationary

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    Rio Rancho
    #15
  16. assquatch20

    assquatch20 Hoss Cat

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    So I thought this might be a decent spot to ask.

    I'm wanting to do the swap on my R75/5 and I'm curious about what throttle/cables I'd need.

    It's got the "US" bars on it now but I'd like to make the switch to Euro's. For that, what cable lengths would I need and will they work with the stock throttle?

    As well, which bore is best for just commuting/touring a little? I'm thinking 32 would make sense, but I don't get why folks are using 38's and such.
    #16
  17. Kt-88

    Kt-88 I like everything.

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    I think 32's will work with the stock throttle cam.
    #17
  18. wolfy317

    wolfy317 Addicted to BMW

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    Ooh, glad I found this thread. I am very soon to be putting some mikuni's on my 71 75/5! Except that my /5 has r90s heads/cylinders/carbs....I'm thinking of getting the vm34's, but my concern is cabling? Where are you getting your cables from, or are you using custom kits?

    Just saw I'm repeating a question somewhat. I actually have some old Honda bars on mine now, but I'm thinking of getting the euro bar as well.
    #18
  19. hardwaregrrl

    hardwaregrrl ignore list

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    I bought my cables from Bill at rocky point cycle and they are a thing of beauty!!! Very easy pull and easy to sync with the inline adjusters. I highly recommend that route vs bodging route, which I did initially.
    #19
  20. Velocipede

    Velocipede Been here awhile

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    How did I miss this thread?I have a pair of VM38's sitting at my shipping address in NY.This info is going to be so handy once I get them installed plus get my Endurolast stuff dialed in.Thank you all.
    John
    #20