Repacking Modern Trials Bike Muffler-Ends

Discussion in 'Trials' started by motobene, Feb 24, 2019.

  1. motobene

    motobene Motoing for 49 years Supporter

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    I appreciate that, thanks. I wasn't 'offended.' I accept the risk in presenting ideas, especially new ideas.

    More like slightly chapped about the comment about 'over thinking', when it's actually thinking at a higher resolution. If engineers stayed safe and thought at lower resolution to stay clear of 'over thinking', our motorcycles might still look like this:

    Old.JPG

    I had never before considered re using muffler packing either, until I got in there and saw what was there. It's a 2-year-old bike, so not like it had a million hours on it.
    The cookied (coked)-up first wrap around the core looked unrecoverable at first, but it burned out nicely. I showed only the pic of the thin layer of pink insulation laying over the recovered area just before being rolled tight. You can see the white-ish look of the burned out fibers just above the pink stuff, however.

    Regarding repacking a 2008 GasGas, I did those before, like on my 2005 GasGas. That's the old-style final muffler with straight-in design and constant cross section from one end to the other. The new designs are integrated into the center muffler and more compact and swoopy looking. A consequence of compact and swoopy is significantly more difficult packing installation because the muffler exit at the cap is radically tapered down. Someone's high resolution (over) thinking was the Rasta hair. Mat packed in there will work, it's just more of a pain to get in there. And the perforated tube isn't straight. It's super difficult to guide it home from the inside of the tube.

    D2W, the 4-stroke packing idea is good, thanks. The mat I found in the Sherco was much denser than I expected. On the newer designs - Sherco-Scorpa at least - there is no way to push all of the packing in at once, maybe. I just think I'd've gone insane trying it, and the packing would have gotten all torn to hell.

    Does the Rasta hair packing sound deaden more than mat? I'm guessing yes, but I haven't tested it so that's just a religious comment.
    #21
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  2. motobene

    motobene Motoing for 49 years Supporter

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    Why not just leave it alone and see how long it lasts? It could be your work will last just as long as the Rasta stuff before getting poppy. What made for poppy anyway was not what was farther from the perf tube. It was the part that was in contact with it.
    #22
  3. Norman Foley

    Norman Foley Devotee of the Husqvarna Supporter

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    Interesting how that bike, has evolved into this....
    [​IMG]
    #23
  4. Brewtus

    Brewtus Buffoonery, Inc.

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    Some years ago, I was given a bag of "Rasta hair" muffler packing to try out, the manufacturer was wanting feedback. The instructions were to pack it in very tightly. My test subject was the FMF Turbine Core silencer on Miss Bitters' 315R. After removing the packing and bead-blasting the core, the perf. tube went back in and I packed the hair in around it very tightly with a paint stirring stick. Reassembled the silencer, test. I gotta say that bike was extremely quiet for over 2 years until the packing coked up. Repacked it with FMF packing after that, bike was never that quiet again. Don't remember the Rasta hair packing manufacturer unfortunately, but I'm sure a Gooble search will reveal something.

    Just my 2 cents. :D
    #24
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  5. motobene

    motobene Motoing for 49 years Supporter

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    Hmm. I wonder what Google search terms to use to find the hair....

    The following SilentSport packing is at least stringy:

    upload_2019-2-28_9-16-59.png

    Found the above pic in an ADVRider post about muffler packing. It's not as thick or fluffy as the Rasta hair from Yurp.

    Does the above look like what you stuffed into Miss Bitter's 315R, Brewtus?
    #25
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  6. Boom Boom

    Boom Boom Been here awhile

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    The Beta Rev3 always had a pop pop to the exhaust tone. I would burn off the baffle well then wrap with the FMF sheet material and hold in place with a minimal amount of tape. Once the heat let the tape fail the packing would be blown away from the baffle and create a pocket between baffle and packing. Would last a long time as never got to the oil soaked or burnt tight stage and reduced the pop pop tone by a modest amount. The 16 Scorpa had to much open space all around that even with stuffing the loose materials back in when the tape failed the packing just moved to much so redone again with the wire and tape as Bene has shown. The older Gas Gas / Beta / Montesa with oval exhaust I had good luck with the let the tape fail and packing move away from the baffle.
    #26
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  7. Brewtus

    Brewtus Buffoonery, Inc.

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    That's the stuff!! :thumb Thanks, just in time to clean/repack the FMF on Miss Bitters' Montesa, and the OE silencer on The Rat. :D
    #27
  8. Junglejeff1

    Junglejeff1 Long timer

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    I will be going through my 2015 GG next month and packing exaust is on the list.It,s good to have projects as we are getting dumped on with snow.I will take your suggestion and take some picks of the work I do to bike and make a thread on it.At the moment have my hands full with my old ty I am doing a thread on.
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  9. motobene

    motobene Motoing for 49 years Supporter

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    Cool!

    Given this thread covers all the moderns in the title, posting here instead of creating a new thread is suggested.
    #29
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  10. wheelieman14

    wheelieman14 Been here awhile

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    It seems like exhaust silencer packing is one of the most overlooked (neglected) things in Trials bikes. I know my current stable to Evo bikes all need to have this done and I bought OEM packing from Beta to prepare for the task at hand. I also have several versions of silencer packing (2T & 4T) to freshen up my bikes for the season, so this thread is very helpful to consider what works best. Thanks bene for your contribution and photos - which I find very helpful. It seems that when we are plonking around with rather low engine revs, there is an accumulation of oil in the silencer and then when an occasional high speed run happens and raises the exhaust temp; there is an embarrassing amount of smoke bellowing out. I'm hopeful that fresh packing will quite things down a bit and possibly improve performance for a while.
    #30
  11. alpineboard

    alpineboard Been here awhile

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    IMG_1062.JPG IMG_1064.JPG IMG_1066.JPG IMG_1067.JPG https://advrider.com/f/threads/beta-evo-thread.1007749/page-32#post-35398415

    Wheelie, on the evo , you will see that the perf tube is at a difficult angle, so one side of your repack needs to be thinner, I did the wrap and used regular wide paper masking tape, then at one end , where the pack needs to be thin, I shaved little slices off, one slice at a time, with a very sharp knife, shaving this tape at the same time, then wrap some more tape on it. This worked well as the tape held it together , as it got shaved. Also tricky to get this pack back in, and insert the plastic end, takes a bit.
    My glass was partially gone at the inner end of perf tube. Everything else looked fine. Using what Rocky mt was selling at the time, 1/2 inch blanket type.
    First 2 pics show gone portion at the thin area. Second 2 pics shows how thin the blanket has to be and the weird angle needed to get the perf tube in and the weld stud that is also in the way. Took me approx. 20 to 30 minutes , then it slid right in. But the thickness of blanket at the thin spot is a guess, but it is needed there , as that is where it starts to degrade first.
    Have approx 60 hours on it after repack and is fine, but that is not saying much.
    #31
  12. GrahamSeychelles

    GrahamSeychelles n00b

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    Great tutorial, well written. Thank you. Its a great help
    #32
  13. Hoss Cartright

    Hoss Cartright 219.474.6657

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    Would you be so kind as to also explain why the maintenance of the exhaust is not only about noise but also relates to the engine's power characteristics and how this changes when the interior perforations of the cores of the expansion box and silencer become clogged with carbon and the acoustic/sonic bounce-back waves can no longer migrate into the packing material as per the original design.

    I think few people realize the science of this and why the core perforations being open and the packing not being clogged are important for engine performance.

    At the top levels of this sport, the center exhaust and silencers are frequently rebuilt or changed on the factory bikes.
    #33
  14. Chad M

    Chad M 14880

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    I’m curious as well about the density part. I repacked my muffler using the FMF mat and not surprisingly ended up using almost the exact method described here to get everything back into place. My “over thinking” part came at the point of stuffing the loose strand around the core. I couldn’t decide whether to pack it in very tightly or somewhat loosely around that core wrap. In the end I chose moderately tight packing, reasoning to myself that the exhaust waves should be always to penetrate the packing more easily, but not too easily (lol) to get the full damping effect of the material. In my mind, a super tight packing would in essence restrict the exhaust to the core inner diameter. Phew... so glad to get that off my chest, haha.
    #34
  15. Takataka

    Takataka Been here awhile

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    My bike (TRS 250) was getting very loud after approx 210 hrs use.
    I repacked the muffler a couple of times with different methods but only got a moderate improvement.

    Last week I took the bike on a trail ride that had some huge extended hill climbs. The pipe heated up nicely and poured out a lot of smoke. It's definitely a bit quieter now and just generally running better.

    Is it considered worthwhile and safe to remove and burn out the front section of the pipe with a heat gun or flame?
    I have seen where some have cut it open to clean it out but don't really want to do that at this stage.

    BTW I use motul 710 at 90:1 and don't just putter around all the time but still get quite a build up obviously.
    #35
  16. riabma77

    riabma77 Been here awhile

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    Great thread. A lot useful information. I started removing the old packing. It seems a few saturated to me, but it's my first time dealing with this.

    It called my attention that the inner tube is wrapped with a metallic mesh. I think is a good idea (from the previous owner) to prevent the holes to get clogged.

    Bike is a 2013 GG TXT Pro. I found a couple of places online that sell the original tube with the packing already installed, with a specific OEM part number. A few more expensive but not sure if it's worth it. IMG_20200302_155928.jpg IMG_20200302_160514.jpg
    #36
  17. riabma77

    riabma77 Been here awhile

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    I finished repacking the silencer Today. I didn't install the metallic mesh, and didn't packed it too tight. In fact, it was very easy to install. Only for testing. I will open it again in a few weeks, to see what I find.

    Attached Files:

    #37
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  18. Zuendapp

    Zuendapp Been here awhile

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    I am not sure of all brands, but Sherco / Scorpa offers a new assembly for the newer models.
    No muss, no fuss, no unpleasant bending.

    DSC01084.JPG
    #38
  19. riabma77

    riabma77 Been here awhile

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  20. Ride Sally Ride

    Ride Sally Ride Is that what you're wearing? Supporter

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    Does anyone have experience doing this with a pipe that doesn’t have a removable end? (Forgive me for probably talking about it incorrectly. )

    I have a 2005 Sherco 125. The tailpipe is all one piece.

    image.jpg

    Where as my husband’s bike is a newer bike and it looks like this.

    image.jpg

    Is cutting it apart and then welding it or trying to catch it on fire the only options?
    #40
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