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Scrambler Exhaust Build

Discussion in 'The Garage' started by Forde, Jul 11, 2019.

  1. Left

    0 vote(s)
  2. Right

    2 vote(s)
  1. Forde

    Forde XS400 Member

    Hi everyone, it's been quite a while!

    Ever since the newest Triumph scrambler came out, I have been pining after a pair of high pipes. Couple that with my friend purchasing a cabin in Northern Wisconsin (offroading trails like you wouldn't believe), and you have the recipe for entering into a scrambler pipe build.

    Now I have searched the forum high and low for a custom exhaust build but nothing has quite reached the level of detail that I am looking for. Long story short, I want something like a CL350 mixed with a Triumph scrambler (see pictures). That means a left side exhaust that runs over the stator to just behind the rider, but with some interlocking bends and some great heat guards. However, I have not seen something like this done for a '78 SOHC

    My question is what should I be looking for in terms of exhaust diameter based on the stock dual walled headers? I have read that 1.5" OD could possibly work, but would 1.375" or 1.25" be a better idea? What would a good inner diameter be? I already have an open exhaust that seems to be tuned right and runs well enough to go 100+ miles at a time.

    FYI I will be having a company do mandrel bends in 304 and then TIG it together myself with the appropriate engine mounting points and a dime city cycles reverse cone muffler.

    Here is my XS, and my inspiration.

    Also I recognize the pipes are a bit blued from running lean. That is from the previous owner.
    XS400.jpg Triumph.jpg CL350.jpg

    Attached Files:

  2. sandmanred

    sandmanred XS400 Addict

    If your stand is on the left I'd put the pipes on the right, it shows them off the best when the bike is on the stand. Sorry I can't help with the math or theory on pipe design. I've done a few exhausts and always been able to get the bike to run well across the whole throttle and rpm range. I like to include a removable baffle at the exhaust exit that gives me another thing to tune with. I adjust the restriction by slotting or welding up holes in the baffle. The first two bikes I did I was able to re-tune the bike with baffle mods only. My XS400 required re-jetting after I went as far as I could with the baffle.
    Forde likes this.
  3. Forde

    Forde XS400 Member

    @sandmanred thank you for the baffle idea and design considerations, that makes a ton of sense. Those baffles could be almost like the snuffler nuts on the old CL77s.

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