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Thread: V Max. How many disc's

  1. #1
    carsten c Guest

    Default V Max. How many disc's

    Hi a question from a frustrated V Max owner in Denmark
    Recently bought a 94' v max with stock exhaust.
    Along came a set of ST megaphones. I've mountet it on my cycle, but it seems to be at lot harder to start now. Needs more choke, and needs more warm up before i can twist the throttle without choking the engine.
    Also if i rev it to about 4-5000 rpm it is very slow to settle back into idle. It was not that way before i mountet the Supertrapp.
    Mine exhaust came with only 2 discs mountet, but with washers in between the discs to make some gap. My guess is that the previous owner used the washers instead of buying more discs.
    But the question is, is there a guideline to how many discs i should put in. I've read that 6 pr side should cut it, with standart carb settings..
    Last edited by carsten c; 02-04-2012 at 06:04 AM.

  2. #2
    Join Date
    Aug 2008
    Location
    Blackfoot, ID
    Posts
    120

    Default

    What you're describing sounds like the STs are flowing a lot more than the stock system. Stacking or spacing diffuser discs like the previous owner has done kind of defeats the purpose of how STs are engineered. The idea is to take advantage of molecular gas expansion. The PO kinda skipped that part for some odd reason.

    In any event, yes there is a SuperTrapp tuning guide under the main site's Resource Center, FAQs. Based on how you're making the bike sound, it probably needs tuning, either overall mechanically or just at the carbs (I assume it's carbureted) and later the STs.

    Keep us posted. I'm curious to find out if your VMAX was already modified/rejetted and/or if there's other mechanical issues.

  3. #3

    Default

    Quote Originally Posted by carsten c View Post
    Hi a question from a frustrated V Max owner in Denmark
    Recently bought a 94' v max with stock exhaust.
    Along came a set of ST megaphones. I've mountet it on my cycle, but it seems to be at lot harder to start now. Needs more choke, and needs more warm up before i can twist the throttle without choking the engine.
    Also if i rev it to about 4-5000 rpm it is very slow to settle back into idle. It was not that way before i mountet the Supertrapp.
    Mine exhaust came with only 2 discs mountet, but with washers in between the discs to make some gap. My guess is that the previous owner used the washers instead of buying more discs.
    But the question is, is there a guideline to how many discs i should put in. I've read that 6 pr side should cut it, with standart carb settings..
    Hi Carsten,

    You will want to use 8 discs per side with a totally stock bike. If you richen up the carbs then you will need to add more discs, 2 at a time until you get the ride you want.

  4. #4
    carsten c Guest

    Default

    Thank you for the replies both of you.
    Yesterday i mounted the end cap only with 2 washers pr bolt. That makes a gap of approx 4-5 mm. The bike was much easier to start, and it didn't rev on it's own like with free flowing mufflers. It surprises me to learn that back pressure in a 4 stroke exhaust is that important. Ofcause i am aware that it's a question about jetting with open exhaust..
    Well i'll try to find some discs here i Denmark. Or maybe i have to order from the States, but it's a helluva lot in custom taxes andshipping charge..
    I'll return with hopefully a happy ending once i get hold of the discs

  5. #5
    Join Date
    Jul 2007
    Posts
    443

    Default

    Check with one of our EU distributors, most are Harley related, but they carry the same 4" disc packs.

    Zodiac.nl
    Parts Europe
    Custom Chrome Europe
    W&W Cycle

  6. #6
    carsten c Guest

    Default

    Well now i managed to find some discs. First 7 per side and now I am down to 2 per side ... And even tried to adjust the mixture screws both to the rich and lean side. But still it revs unmotivated up to 3-4k rpm without me rolling the trottle, only way to kill it is the killswitch/key.. If i start it again, it catches rpm's again, sometimes dropping down into normal idle again... since it was running okay last year with stock exhausts, I find it hard to believe that there's something wrong. So yesterday I mounted the stock exhausts again, and the bike runs perfect as before..
    It can't be right to remove any more discs, can it... So confused

  7. #7
    Join Date
    Aug 2008
    Location
    Blackfoot, ID
    Posts
    120

    Default

    Sounds like an intake boot air leak. With the engine cold and started, try running hose water over the intake boots to see if the engine RPMs dip.

  8. #8
    carsten c Guest

    Default

    Yes that sounds that way.. But I've refitted the original exhausts just the other day. And now it runs smoothe as before I put on the supertrapps.. The problem is only with the trapp's mounted

  9. #9
    bschultz Guest

    Default

    Logically the advice given sounds correct and should have corrected the issue; however you may have too much fuel being delivered and need more flow. Have the stock pipes been altered? Did the previous owner do any jetting?
    Have you tried running the SuperTrapp pipes without the end cap and discs (wide open)?

  10. #10
    carsten c Guest

    Default

    Problem solved... I did change the intake boots cause there were some cracks in them. But that didn't help.. Then I rode a few miles with the original and later the trapps, still the same problem with both exhausts.
    Took it to a mechanic at ran it on a dyno. Idle and low end throttle sucked big time. He wasn't able to adjust the mixture screws right. To lean A/F ratio. But from 1/4 to full throttle it ran perfectly..
    So when I got home, I cleaned the carbs idle circuit.. And now it's top notch.
    Should have thought of that. But was so obsessed with the fact that it ran perfect before I put it away for the winter.
    I run 8 discs per side now. Would love to run gutted, it's the most heavenly sound, but that will be to noisy..
    Thanks for your advise, allthough it was my own mistake...

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