Stealth trials?

Discussion in 'Trials' started by SlowRide13, Feb 7, 2013.

  1. lamotovita

    lamotovita Ageing Adventurer

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    I believe there are two different silencer cores for your bike. A straight one, and a curved one. If yours is straight you might see if you can get a curved one for it. You could also add a spark arrestor if you don't have one.
    #21
  2. GrayEagleRider

    GrayEagleRider Been here awhile

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    Mine has the curved one, will have to check on the spark arrestor next time I make a parts buy. Thanks
    #22
  3. motojunky

    motojunky Professional Idiot

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    For a simple test, measure the OD of the exhaust outlet and stop in to the local auto parts store and grab a 90 degree hose with an ID that's in the ballpark (think water pump inlet hose). That and a clamp should give you an idea how effective it'll be.

    After hearing your new neighbors moving in the other night, I'm thinking that your exhaust isn't going to get anyone's attention! :lol3
    #23
  4. motojunky

    motojunky Professional Idiot

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    Does anyone recall the sound level of a new Scorpa SY250? I just had the mid-box repaired and silencer repacked on my 2002 and was a little bit disappointed with the level of sound reduction. It's better, and not obnoxious, but still not as quiet as I would like. Fortunately it's a non-issue with my neighbors, I just like quiet bikes.
    #24
  5. lineaway

    lineaway Long timer

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    The montesa originally came very quiet. There was a header restictor, a mid pipe restictor, and an intake. If you could find the mid-pipe restictor, that would probably do it. I`m sure I tossed all I had!
    #25
  6. ADVCoop

    ADVCoop Been here awhile

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    This is my stripped down '92 Contact 250. It's pretty loud. Since I don't think it the silencer is re-pack-able, I am either going to try to find a different silencer or make a turn down tip for it to see if it helps. I wanted to be able to ride in the woods here beside my house but it's way too loud for that. My neighbors will surely complain like they used to when my nephew rode his CR80 here haha.

    Any ideas?

    [​IMG]
    #26
  7. motojunky

    motojunky Professional Idiot

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    The silencer is "re-packable," just not in the traditional sense. They can be cut open, re-packed and welded back together. Nowhere near as easy as drilling out a couple of rivets. My Scorpa is this way also. I have no means to weld aluminum, so I had someone do the job for me. I have contemplated building a new silencer but I'll almost certainly never act on that.
    #27
  8. ADVCoop

    ADVCoop Been here awhile

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    Hmm, I can't weld aluminum either, only steel. So repacking is out for me.
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  9. hoffa509

    hoffa509 Adventurer

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    For a two stroke, if you can find a used db snorkel on ebay http://www.thedbsnorkel.com/howitworks.php you would be set. A guy from my old club had one on his KTM200. It really reduced the noise.

    Or ride an old Reflex like me. My neighbors never know I am riding.
    #29
  10. motojunky

    motojunky Professional Idiot

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    I have seen those dB snorkels online, but never in person. Good to know they work. I'm fortunate that I have no neighbor issues, but I'm of the opinion that quieter is better no matter where I ride.

    BTW, did you see the post on the TST mail list about 2/24? Will you be able to make it?
    #30
  11. ADVCoop

    ADVCoop Been here awhile

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    I was kind of bummed when I heard the dB snorkel went out of business. They actually worked, they were just goofy looking. I might have to try to make something similar or find somebody selling one on eBay like you suggested.
    #31
  12. LeShaghal

    LeShaghal Adventurer

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    IMO a "Stealth" bike its one that just mumbles along at idle
    Seems once any bike gets off idle its clearly audible, just the nature of the beast

    On the old GasGas mufflers,
    If you judiciously hole-saw a hole in your muffler you can, using a coat hanger, strip out all the old glass and repack it. wipe down the outside with solvent (Acetone, De-natured Alch, or my favorite Lacquer thinner) and put actual DUCT TAPE [The aluminum stuff used on ducts and chimneys] to cover the hole. Leave tons of overlap and roll it down hard. It's not Ideal but its cheap and easy.

    The most effective thing I've found BY FAR is to make sure the back box (muffler) is sealed tightly to the mid-box, and the mid-box to the header! High-heat silicone gasket material or dedicated exhaust silicone does the trick, a leaky junction in either will get the neighbors on the phone in a hurry.

    Also you might take out your mid-box and weigh it. When they coke up Hard that *Tabuga-Tabuga-Tunga-Ungh-ung-Ungah uh uh uhh* type noise Becomes a Crisp barking crackle of *WHOP-Pap-AH-WHOPA-WHOPAP-WHOP-PA-Pah-POP ah* type noise. When I got my first GasGas the mid box weighed 13.2lbs, a week's worth of De-coking later she was down to a mean lean 11 (And I still don't think I got it all out!) but It's noticeably quieter.

    I ride a lot of urban stuff, just tooling around town, and even with repacked boxes, airtight flow, and careful Idle adjustment we've never been able to make one "Library safe"

    It's always been my understanding that the mid-box acts as a pseudo-expansion chamber/TunedPipe, so anything after that is just auxiliary suppression. Should that ring true...if you were deadly serious about it, you could just use a big muffler off an enduro/Dualsport bike to tame a trials machine?
    Ha! those beastly sized cans on BMW's :rofl
    #32