Latest exp. chamber set-up

Discussion in 'Performance Mods' started by a/c man, Jul 5, 2010.

  1. a/c man

    a/c man Member

    This is my latest configuration on my 2nd expansion chamber "experiment"
    I went with larger diameter 1 1/8" diameter tubing instead of the customary
    7/8" in an attempt for more breath-ability since these pipes were originally designed for 47-49cc pocket bike engines.

    I had to fabricate my own flange, but that was a good thing since I could make the opening much larger to match the exhaust port on the engine jug.

    Gone is the worry of burning my leg on the pipe since it's down by the bottom bracket. I also got to keep my kick stand.

    This is one of 2 pipes I got on E_BAY. I picked them up for $10 a piece on sale in March or so. Actually he mailed me 2 but I only paid for 1!!!! That's $5 a piece.

    Power is noticeably better than stock, but about the same as my other pipe I had previously.

    It tucks nicely between the peddle cranks and rear tire.
    It's all brazed up since I'm not really keen on the look of the silicone couplings that are out there. Looks a little more clean. It's 12 inches from the engine port to the start of the 1st cone's taper. Jetting stayed at .70mm.

    Attached Files:

  2. GearNut

    GearNut Active Member

    I like that. Nice, clean install!
  3. lepooner38

    lepooner38 New Member

    Good looking install.

    Is that copper pipe/fittings used in this build??
  4. AussieSteve

    AussieSteve Active Member

    Very nice looking, a/c man.
    You said 'Power is noticeably better than stock, but about the same as my other pipe I had previously.'
    What was the previous pipe? The reason I ask is that I'm wondering if it was an SBP pipe. ie How your new pipe compares to an SBP one.

    The 'header' section is very long. What rev range is it tuned for? (Looks to be down low.)
  5. a/c man

    a/c man Member

    Steve, although the header pipe may appear to be long, it is only 12". Yes its copper.
    This is the same length that SBP recommends for their pipe.
    My pipe is very similar to theirs except it is straighter. The links #1 and #2 below will compare my pipe to a pipe virtually identical to theirs.

    My first pipe was a stock pocket bike pipe which I cut and lengthened the center section, worked great tons of low end grunt, top speed 39.8 mph.
    Attachment below is that pipe. Header pipe was shorter 10"

    My new header pipe is far larger in diameter and the flange opening fits the port opening nearly perfectly. The stock flange that comes with the engine kit, and the pocket bike flange were both way to small internally. They choked the opening size down a lot.
    . The stinger is a bit smaller in diameter than the 1st pipe, and the silencer is just slightly louder.
    Anyway you slice it, any pipe is by far better than the stock "kit" pipe.
    Baffled or un-baffled they suck.

    Attached Files:

  6. AussieSteve

    AussieSteve Active Member

    It just looks longer in the header than the SBP one.
    It's a neat fit on the bike, too. Good job.
    I've got an SBP chamber here, to fit when I get to it. I won't use the silicon etc, though. I'll get the muffler shop to bend and weld on a one-piece header. 12" sounds good.