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New Exhaust,Weaker Motorcycle...

Discussion in 'Equipment' started by tomasmaria6, Jun 28, 2020.

  1. tomasmaria6

    tomasmaria6 Adventurer

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    Fellow riders
    I have equiped my R1100 GS 1994 with a dominator exhaust. Quite happy with the result regarding aesthetic and sound (bit noisy, but not that loud as previous read on foruns) the thing is once i ride the bike when i get past 130km/h the trepidation is so massive that the bike just doesnt feel safe to me, the handles are shacking till my wrist gives up and the mirrors basically loose their function, blurred completely.
    Last, but not least, the speed...god the speed, seems like i went from a 1100GS to a PCX :(
    The bike makes a lot of noise when i accelerate but seems to have lost the propulsion completely, and i thought a new exhaust would increase my motorcycle performance...

    What is your feedback?
    Thank you guys
    #1
  2. blender

    blender Just another rider

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    Loudness does not equal performance. Put the stock exhaust back on.
    #2
  3. PeterW

    PeterW Long timer

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    More modern bike I'd agree. Odds are there's something else wrong that's been exposed by the new exhaust , I'd guess the exhaust valves aren't seating properly but I could be totally wrong on that.
    #3
    tomasmaria6 likes this.
  4. oldmanb777

    oldmanb777 Just say NO to socialism! It's a bad drug!

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    If the mixture, timing, compression, cams and all the other things that go into making an internal combustion engine work properly, are miss-matched, it will not run as well. Changing the exhaust just screwed up everything. So now in order to make it run properly, you need to adjust all the rest to match the exhaust. And since all the professional engineers spent years making it all run well, you may not be successful in a weekend.
    #4
    Bigger Al likes this.
  5. MotorcycleWriter

    MotorcycleWriter Vis ad locum

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    A new exhaust is the single biggest overpriced gimmick peddled to performance enthusiasts of both cars and motorcycles.

    You must think of engines not as a bunch of components, but as system. The components are chosen and tailored to work together in the expected operating range of your vehicle. Even before the sophisticated fuel-air maps recent-manufacture cars bikes use to gets lots of power while minimizing emissions, slapping on high flowing exhausts, manifolds, and carburetors often produced disappointing results.

    The interplay of physics, chemistry, and engineering is incredibly complex and usually beyond the interest of amateur enthusiasts. Manufacturers spend years and millions squeezing efficiency from their engines.

    In your case, you’ve altered the fuel air map and the inertial properties of the flow. You’ve made it both too lean and shifted the horsepower curves to the right while also making them more peaked. And when it comes to these boxers, if you want more power you’re really better off getting a different motorcycle. They aren’t designed to produce peak power, ever, and it is very expensive to make them both ridable and powerful.
    #5
    Bigger Al and oldmanb777 like this.
  6. brianbrannon

    brianbrannon They'll ride up with wear

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    What else was done at the same time?
    #6
  7. Bluesmudge

    Bluesmudge Been here awhile

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    New exhaust requires free flowing air filter and re-jet (carbs) or re-map (FI). For carbs its worth the extra $200 to let a shop with a dyno set the air-fuel ratio or you will spend years on forums and playing with the carbs trying to get the jetting correct. With a dyno they can do it with one or two jet changes.
    #7
  8. brianbrannon

    brianbrannon They'll ride up with wear

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    Fuel injection doesn't have jets to change. Nor is it likely that just changing the exhaust could cause a running issue on a fuel injected engine.
    #8
  9. davidji

    davidji bike curious

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    I agree, though at least on my SSSA BMW boxer, replacing the can made sense from a functional perspective: with a thinner can, the rear wheel was easier to remove. It's the only bike I've replaced the stock muffler on.


    Probably should reinstall the stock exhaust. Did you replace the whole exhaust, or just the muffler? Are you running the new muffler with the baffle installed?
    #9
  10. Bluesmudge

    Bluesmudge Been here awhile

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    Thats why I said re-map for fuel injection. Unless the new exhaust is just a slip-on with flow similar to stock (I'm not familiar with the exhaust mentioned by OP), the fuel injection system won't accommodate a drastic change in fueling needs of a full un-restricted exhaust without a re-mapping of the fuel system. You are right if the exhaust is similar in flow to the stock pipe a modern FI bike should not have any issues. However, I don't think older FI bikes are smart enough to change fueling on the fly. For example, my 2003 BMW R1150RT still has a manual "choke" because the fueling system isn't smart enough to warm itself up.
    #10
  11. markk53

    markk53 jack of all trades... Super Supporter

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    Many manufacturers of exhausts will say a remap is necessary to get the full performance since there are parameters that the OEM injections works within. So if the exhaust requires it, a remap may be necessary. I got an exhaust for my Yamaha specifically looking for one that requires no remap and has lower dB. I got it for looks and a bit better tone, not louder, but better. It will be a bit louder, but not to the point of distraction of everyone within four blocks... or one for that matter.
    #11
  12. brianbrannon

    brianbrannon They'll ride up with wear

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    They say that for marketing purposes. OEMs tune rich at full throttle for safety and warranty. There's no EPA testing at full throttle so they dump fuel. At other than full throttle the throttle plates are going to be partially closed and will be the primary restrictions. The OPs engine makes so little power even a tiny stock exhaust wouldn't be a restriction
    #12
  13. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    You must either re-map or re-jet when you use a new exhaust or a new freer flowing air cleaner. If you didn't need to, your new modification isn't working any better than what you had on before.
    #13