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mikuni vm32, how much scratch?

This is a discussion on mikuni vm32, how much scratch? within the Vintage Motorcycle Racing forums, part of the Caferacer.net Forums category; quote: Originally posted by UngaWunga I'll bet ya that those 32mm are too big for your engine. What's the stock size? I believe the stock ...

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  1. #11
    Senior Member freedomgli's Avatar
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    quote:Originally posted by UngaWunga

    I'll bet ya that those 32mm are too big for your engine. What's the stock size?
    I believe the stock CB350 Keihin CV-type carburetor venturi bore is 28mm. It seems most people recommend the Mikuni VM32 for my bike. One person (whiskeysid) recommended the VM30 although that might be a typo as I thought he previously mentioned he's got VM32s on his own CB350. And it seems krapfever has either VM28 or VM32.

  2. #12
    Senior Member kenessex's Avatar
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    The stock CV carbs flow about the same as 28mm slide needle carbs. You can't really compare the flow of CV vs VM style carbs because of the 2 butterflies and shape of the slide in the CVs. Generally speaking, a stock CB350 with pipes can't use more than a 30mm VM carb. A built motor can use up to 32mm VM style, if it is really built. A mildly built motor will probably be better off with 30mm VM style carbs. My motor has OEM 4th over pistons, ported head, Type 1 cam and 2-1 pipe. On a long straight I feel like it is just running out of carb on top. That is with properly jetted stock CV carbs with the choke plates removed, stock velocity stacks and uni-filters. I am going to try 30mm VM carbs. On an earlier motor in the 80's I had a built motor with big bore High CR pistons, webcam, ported motor and pipes and I used 30mm Lectron flat slides that worked well. I think people tend to over carburate their CB350s.

    Ken
    WERA 119
    CCS 119
    CRA 119
    AHRMA not anymore
    \"Think twice before you speak, and then you may be able to say something more insulting than if you spoke right out at once.\"
    Evan Esar
    Newbies, Geeto and Tex (Bye Tex)hate me!!

  3. #13
    Senior Member 736cafe's Avatar
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    the only reasons i chose the vm32's are that i have a built motor(362 thr pistons, lumpy cam, and a mildly ported head). that and the deal couldn't be argued with.
    anybody need a set of uni filters and an aluminum fork brace for an sl350?
    scott from chicago
    (ahrma 527)

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  5. #14
    Senior Member UngaWunga's Avatar
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    Ok then.. that's different. Listen to Kenessex.

    Flat slides flow more per diameter than round slide carbs.





  6. #15
    Senior Member kenessex's Avatar
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    Unga is right. Flat slides are gooder than round slides, but AHRMA doesn't like them.

    Ken
    WERA 119
    CCS 119
    CRA 119
    AHRMA not anymore
    \"Think twice before you speak, and then you may be able to say something more insulting than if you spoke right out at once.\"
    Evan Esar
    Newbies, Geeto and Tex (Bye Tex)hate me!!

  7. #16
    Senior Member UngaWunga's Avatar
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    No, FU! You're right!





  8. #17
    Senior Member freedomgli's Avatar
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    Thanks for the feedback fellas. My motor is stock so it would seem that VM32 would be too much carb for my bike. In my experience working on cars a throttle that is too large can hurt intake velocity and throttle response. My engine won't be sucking as hard as a 362cc THR kitted bike that revs to 12k rpm so I should consider going with the slightly smaller VM30 (set up for 4-stroke motor, of course). Anybody else run VM30 on the street?

  9. #18
    Senior Member parks61's Avatar
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    hey ken (aka mr. sex)
    i've never heard a good reason as to why flat slide carbs are "gooder" than round and would love to learn something new. is it a small throttle response advantage or a full throttle breathing advantage...or both or neither?
    -parks
    I\'m not handsome

  10. #19
    Senior Member kenessex's Avatar
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    Parks,
    I don't know the why of it all. I just "know" that generally speaking a motor that is happy with an XXmm VM will be just as happy with an XX -2 mm flat slide. I have never stuck a VM and a Flat slide on a flow bench to check it out, either.

    So I am just going with Unga being right. So FU back Unga!! You can be righter than me, this time.

    Ken

    WERA 119
    CCS 119
    CRA 119
    AHRMA not anymore
    \"Think twice before you speak, and then you may be able to say something more insulting than if you spoke right out at once.\"
    Evan Esar
    Newbies, Geeto and Tex (Bye Tex)hate me!!

  11. #20
    Senior Member crazypj's Avatar
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    Neither Sudco or Sporting for less sell 'correctly' jetted carbs.
    They work, but only in limited rpm range.(usually for racing, at max rpm)
    In mid range or fixed throttle (cruising) they are generally too rich.
    From everything I've read, SFL needs complete re-jetting for road use on a CB350/360.
    Out of the box they have two stroke jetting and all the brass needs changing.
    I've posted a bunch of information on various sites over last 5~6 yrs.
    Is there a link to the $89.00 ones?
    At that price I would get some and re-jet correctly
    PJ
    I dabble in rocket science, when I\'m not picking my nose
    The other night I gave my girlfriend an orgasm, but, she spat it back at me

    'you can take my word for it or argue until you find out I'm right'

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