GEBE exhaust / muffler mod

Discussion in 'Rack Mounted Engines' started by JemmaUK, Sep 17, 2007.

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  1. JemmaUK

    JemmaUK Guest

    I am not sure where to put this, and as its a pic - I though here would be ok..

    I have done a couple of rides now, and the term 'buzzing' is about right - and after a while it can get a little annoying and lead to the start of a headache...

    So I went to the local model shop and had a look what they had in the area of exhaust parts... I was looking for a expansion box.. but what with being in the UK and not being sure what would fit and what wouldnt, I thought I would make something a little like the old 'thin pipe' exhausts on bikes like the cyc-auto.

    This effort cost me £8.50 and about 10 or so minutes..

    Parts used..

    2 x Flexible rubber exhaust elbows.
    1 x brass pipe.
    4 x cable ties.

    I have cable tied the bottom of the exhaust to the rear extent of the deraillier control cable with alot of free play - just as a locator really..

    It doesnt seem to have dropped performance any but is that a possibility?

    Jemma xx

    Attached Files:

    Last edited by a moderator: Dec 18, 2015

  2. bamabikeguy

    bamabikeguy Active Member

    Hey Jemma,

    Didn't know you were a gebe'r :rolleyes: (so many posts nowadays, I barely have time to peek around ).

    Maybe drimpact could snip this, bring it over to Rack em, Hive will be very interested in your muffler modification.

    The rubber works??? You blokes must have better rubber trees than us'ns...
  3. JemmaUK

    JemmaUK Guest

    Hi Bama,

    Given the temperature these things throw out, I wouldnt recommend normal rubber ... The rubber bends I got are specifically designed for exhaust use in model planes etc running .80 - .140 engines.. so they can take the heat.

    It does quiet the engine down some and I will take a short run out to see if it hurts speed any but it didnt seem to - although the test slope outside my flat isnt really a fair test..

    EDIT: just found this - - the silicone tubing would be perfect for a flexible exhaust routing - or for bends/joints.

    Jemma xx
    Last edited by a moderator: Sep 17, 2007
  4. bamabikeguy

    bamabikeguy Active Member

    Good deal....

    When you test, is there anyway to take a temp (Farenheit for us idiots) near the end of that exhaust?

    Just wondering, air cooled and all, what the temp of the far end of the metal reaches, whether the rubber absorbs a lot of the heat, then the pipe, if finagled/manupulented, could serve as "dual use", allow more modification.

    When you think about it, esp. if the pipe circumference was larger, or some kind of "double walled" piping was used, that could make a different angle, and serve as a "frame modification". As a support, as a place to clamp on a red reflector/blinking light...etc etc etc.

    Nothing says it has to go straight, does it? A zig here, a zag there, and it might keep one side of my saddlebags away from the rear wheel/chain workings.

    (oh, and I think you have to send a pm to drimpact, request pruning this thread into Rack em, we can make it the "be all to end all" exhaust modification thread, cuz we don't have the answers yet !)
    Last edited: Sep 17, 2007
  5. gone_fishin

    gone_fishin Guest

    a cheapo conduit bender might could be handy for someone doing this stuff, no?

    'UK, i moved this into the "rack 'em up" techie area, it'll prolly be more effective here...good info, thanks.
  6. JemmaUK

    JemmaUK Guest

    I dont have a method for temp testing - but I know the top end of the pipe gets skin fryingly hot... although it doesnt seem to melt anything...

    Im not sure what you mean by dual use... I think things could be clamped onto it, but only if they arent heat sensitive and not too heavy..

    As to using thicker gauge/bore piping, I dont know as that would work because of the complications of fitting it to the stock silencer out-port... I am no metallurgist unfortunately..

    the more flex points the better for routing - or you could just use the silicone pipe and thats all..

    just some thoughts

    Jemma xx

    EDIT: well, that was fun - speed tested and speed might be down a bit - but I was being more careful. Up until the engine threw the exhaust on a bump... scratch one elbow ... have replaced that (and cabletied it this time). It should be ok & it does seem quieter.

    Joy of joys almost suffered the bane of GEBE - tinkling noise on the move turned out to be the front locking nut on the engine mount... now tightened...
    Last edited by a moderator: Sep 17, 2007
  7. bamabikeguy

    bamabikeguy Active Member

    MB edit:

    Just read your intro, which answered most my questions, cept the girlie part.
    Glad to have you !

    Jemma 2 items

    Hive tried something a month ago with copper, but when it didn't work out like he wished, he deleted the pictures, think he said "never mind".

    Could you edit the thread title, sumpthin like "GEBE exhaust/muffler mod?"

    Second, you didn't mention if you ripped out the screen/spark arrestor on the end of the exhaust?

    If you did, great, but we'll just mention it here, so a reader will see it.

    If you didn't, and you have 7-800 miles on it, that is where the "hiccuping" comes from.

    When did you get the engine? Which drive gear are you using? Have you been avoiding ethanol in the UK?

    You'll be a valuable Gebe'r, once you get thru my interrogations !! :rolleyes:

    Welcome aboard !
    Last edited: Sep 18, 2007
  8. bamabikeguy

    bamabikeguy Active Member


    When you find this thread, AND combine it with framemounting, where a fastener could be added to the newer/securer mount system, (heck, thread the pipe thru an eyebolt, it'll NEVER come loose)...

    Anyway, framemounting is the answer to securing that pipe AND thinking about putting 5 foot of "back and forth" conduit on that side of the bike, a few clothes pins and you could hang your laundry to dry while you ride !! :cool:
  9. bamabikeguy

    bamabikeguy Active Member

    Back to Jemma, (pardon my enthusiasm, I like making a good thing puzzling)

    Okay, think about Augies conduit, two peices, connected with a tee. The Tee sits midway up the mount, the conduit horizontal, about a foot down from the engine

    A "dead end" fastened on the side, under the seat, similar to Hives simple support brace.

    The back end of the conduit, which you've fed the copper exhaust piping, extends all the way out past the back of the tire.

    Okay, back adds a double walled "muffler", can hold a reflector.

    Deadend front provides side support for either saddlebags or in the auxillery tank ideas on 35 R/S.

    Hope you engineery guys can envision it.
  10. JemmaUK

    JemmaUK Guest


    I got the engine about 2 years ago - it has the standard gear and no I am not using ethanol - I know to use what the manfacturer says in engines, a detonating 40 year old 1.6 litre motor thats rarer than hens teeth taught me that..

    I understand what you are saying about the sidemount thing, it makes sense. Trouble is I dont have the tools to do that sort of work and putting any sort of pipe on a rack mount has issues because the only way of routing it so it doesnt poke out the back and look like something you nicked of a spare german V-1 is running the pipe straight down and having a short tail angle. the in-frame mounting is much easier to do as that was the way the old cyc-autos and such were set up.

    I have about 650 miles to go before I have any problems with coking up... the engine isnt even run in yet..

    I have had a look at changing the thread title and I cant seem to find a way of doing it... im pretty much a newbie at forums and such..

    on your question about temperatures. I can tell you that on a 7-8 mile run the top of the metal part is ouchie hot (hotter than the outside of a boiling kettle )and the bottom is about the same temperature as lukewarm water...

    As to lights... on mine I have fitted a cateye LED front and a combined stop/tail/indicator setup on the back with a LED flasher to the bottom left on the other side from the exhaust. I havent used it at night yet but will let you know what happens when I do..

    with the exhaust there does seem to be some backpressure as you get a slight squelch noise just after you have kicked over the compression...

    If I put this kit on another bike - assuming I ever get that far - I will go for suspension - hard-bikes *hurt* - 30+mph across terrain is not condusive to kidneys staying in the right place - it also isnt kind on the wrists...

    Jemma xx
  11. bamabikeguy

    bamabikeguy Active Member


    To edit, go to the top of the thread, post #1, (and the only one that can edit TITLE), add some specific words, and save. Whoola.

    Note I put a blue MB.edit, that is kind of a MBtradition, meaning you found the answer, answered your own question, or made a possibly bogus claim in that post. Usually we leave the bogus part intact, the "blue" signifies we realized our error.

    If you make a bogus claim, and don't correct it, a moddy may put a "red" MB.edit.

    Tools-mimimum to "framemount" a hacksaw, drill and 2 sizes of bits. Don't bother with all my doo-dads, I'm trying to streamline quick installations.

    Curved handlebars, with foam grips and "cruise control" to free up thumb on the throttle, for wide open 10-20 minute spurts, is the key to preventing MB.elbow.
    Last edited: Sep 18, 2007
  12. JemmaUK

    JemmaUK Guest

    Exhaust modification part 2.


    I was relaxing this afternoon and got to thinking... I wonder if the size at the end of the exhaust modification (see picture) would fit the end of one of those beer cans I kept ....

    So I had a look. It fit perfectly with just a small gap at the exhaust end that was easily plugged with Polymorph (meltable moldable plastic)

    So I now have a jerrybuild muffler at the end of the exhaust - I'll just need to test it..

    Pics attached.

    Jemma xx

    Attached Files:

  13. gone_fishin

    gone_fishin Guest

    no WAY! does that work ok?

    hey guys, to everyone: the new board comes with some new procedure: you have one full day to edit your content...after that, you are free to PM the moderator to request changes...talking about it in the thread is not always gonna catch our eye, we can barely just barely read all the new content even when split up into zones. pitch in wherever and whenever you can, pm the forum moddy and help us keep things neat and tidy. thank you.

    jemma...i'd love to hear what that sounds like.
  14. BTB Wild

    BTB Wild Guest

    Yes.....PLEASE report back. I hear the theme to 'Sanford and Son' playing in my head and an image of you and the cops standing beside your bike administering a sobriety test. :lol:
  15. Alaskavan

    Alaskavan Guest

    Do they still make Carling?
  16. JemmaUK

    JemmaUK Guest

    lol, yes they do - it might be that they dont export it.

    As to the muffler it seems to work as a proof of product as it were. The trouble is that I need to make a few changes because the rubber sheared at the top mount because of vibration along the edge of the cable tie.

    I have made a couple of changes to the muffler itself. I've made what is basically a double length single baffle muffler with flare. Its amazing what you can do with a pair of scissors, pliers and sellotape (and yes, I will use heavy duty tape when I can get hold of some).

    It does seem to make a difference, but until I use it on the road I wont be able to tell...

    I am planning to mount the muffler horizontally on the engine side underneath the engine using the upright of the GEBE mount and link to the engine using silicone exhaust pipe..

    Jemma xx
  17. Alaskavan

    Alaskavan Guest

    Don't use duct tape. It's good for a quick, temporary fix, but it can't stand exposure to the elements or changes in temperature. It is no good for ducts. From Wikipedia: "The name "duct tape" came from its use on heating and air conditioning ducts, a purpose for which it, ironically, has been deemed ineffective."
    That said, I wish I had an alternative to recommend.
    On my bike (43cc Mitsu, Staton friction drive), I attached copper pipe and used an improvised bracket and JB Weld. So far it seems to require regular attention, but it does make a difference in sound level. Over time I hope to resolve the problem of it shaking loose.
    Last edited by a moderator: Sep 23, 2007
  18. JemmaUK

    JemmaUK Guest

    New Pics

    Attached Files:

  19. bamabikeguy

    bamabikeguy Active Member


    Why don't you post those pix you deleted on your experiment?

    I would try to describe to Jemma how you drilled that hole in the plastic engine cover, but your pix would tell a thousand words.

    That way this thread can be the place to look for exhaust questions, INCLUDING (one day) step by step instructions in scraping away carbon buildup on the cylinder walls, which is another source of hiccuping after about 1,500 miles or so.
  20. JemmaUK

    JemmaUK Guest


    I have secured the muffler as shown above to the metal protection framing around the fuel tank. I left the elastic support around it (see there are uses for spare hair bands) as a just in case. Attachment method is two large cable ties.

    I have also slowed down the idle on the motor - it seemed that the backpressure was causing the engine to run faster than it otherwise would at idle - and it does sound better at a slow idle.

    I would get at this point about 30-something miles per tankful, does this sound about right - and is a slight blue haze on first starting (from cold) normal?

    UPDATE: Just took Anita out for a run - she purrs - literally - with the throttle off the engine is very very quiet and sounds like a much larger bike. I dont know the effect the adjustment of the idle will have on cold starting...

    Last edited by a moderator: Sep 25, 2007