expansion chamber

Discussion in 'Performance Mods' started by gauge, Sep 9, 2007.

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  1. gauge

    gauge Guest

    DOES ANYONE THINK THIS WILL WORK and will be worth the money my dax 70 barley does 30 mph and need more low end power

  2. gauge

    gauge Guest

  3. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:what is your rear sprocket?

    a 44-tooth sprocket will have lots of low end, and cheaper than expansion chamber.
  4. Hmmm interesting idea BUT that pipe is for a 49 CC engine....In order to maximize the performance of the tuned pipe it has to be designed specifically for a particular engine...Has a lot to do with intake / exhaust opening timing , RPM range etc..Still the pipe may be more beneficial than the stock muffler....Looks to need some minor bending and fab work to get it to fit to the Dax engine....If you do it, let me know if it works cause I have the Dax 70 also....FWIW my 70 also does about 27 MPH max on the std 44 T (lotsa Revs!)...If you want more top end a smaller rear sprocket would be the cure although this would lower acceleration and low end pulling power...

  5. gauge

    gauge Guest

    i have the 44 tooth but i was doing about 32 out of the box i did the exhaust mod with or with out change the needle position the bike now does 28 and its runnig the same rpm. im mad, but now i can only do 15 cause im pedaling for now cause my throttle cable broke
  6. Same RPM and slower speed??...Unless the gearing was changed you should be going the same speed....Maybe the engine just seems slower with the lower tone caused by the exhaust mod?
  7. stinger48

    stinger48 Guest

    check the sparkplug and see if the engine is running lean(dry white to grey colour plug =lean) (biscuit brown colour plug =good) (black=rich) you may need a larger main jet or get yours drilled out, i always set cruise with the needle and flatout is set by main jet ,take your time to get optimum results if its too rich it wont revout or if its too lean will rev to the moon but it will cause meltdown of piston ,in between the two is perfection (power and economy) :grin: expansion chambers are not the easiest thing to make or design or tune.also the standard air filter may not be the ideal choice to go with the chamber ,inlet and exhaust pulses in the manifold have great bearing on power if you get a larger air-filter and you will have to change the jetting .it sounds like a lot of mucking about but can reap double the horsepower!! :cool:
    Last edited by a moderator: Sep 11, 2007
  8. Chuck L

    Chuck L New Member

    I used the exact same pipe on one of my 48cc builds and it worked just fine. I cut the pipe at chamber and after the bend coming out of head and rewelded.the chamber mounts under the bottom bracket and the muffler exits out by the left axle nut.Would show pictures but don't know how to upload yet. Don't know how it would work on a larger but it has to be better than stock.
  9. Pablo

    Pablo Motored Bikes Sponsor

    I can tell you after you port your intake and exhaust, an expansion chamber will make a large difference.

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  10. I put one on my 48cc and like it very much, lots of low end torque. I got mine off ebay for alot less than that. Might want to check it out......

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    Last edited: Jun 20, 2008
  11. alex

    alex Guest

  12. wheelsy

    wheelsy New Member

    hi guys just put a fatboy $28 expansion pipe and silencer off e bay on my bike oh my god what a difference

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  13. fastboy9

    fastboy9 Member

    The low end torque is so nice isnt it! Have you tried matching the exhaust port? heres a thread that goes into detail: http://www.motoredbikes.com/showthread.php?t=5516

    Once you have ported the exhaust you will get about a 30% increase, as the expansion chamber will work even better! Its an essential mod for anyone with an expansion chamber. You have mounted yours the same as mine, do you have any leg clearance troubles? I do a little bit if I wear shorts, but the clearance isnt uncomfortable though.

  14. wheelsy

    wheelsy New Member

    i have only put it on last night my thigh rests against it but only gets warm although i have only taken it for probly 2km ride but it is cool here at the moment to i was thinking of wrapping it in fibreglass tape the kind they use on extractors for cars as a heat shield i have allready shaved the head and opened the exhaust and inlet ports so i canstick my little finger in i have also cut a small piece of the piston skirt off i found when at top dead centre the piston skirt was protuding into the inlet port so i cut it off i also use a different plug and copper lead my son took it for a spin tonight and got 65kmph out of it without wot but it is very loud sounds like a dirt bike
  15. alex

    alex Guest

    Would there be any advantages of taking the fiberglass packing out of the silencer?
  16. Simon_A

    Simon_A Member

    Not really for a 2 stroke. For a 4 stroke maybe, but 2 strokes get their oomph from the expansion chamber.

    Wheelsy, if you put exhaust wrap on your expansion chamber it moves the powerband a little higher in the rev range. This is due to keeping the heat in the chamber and not allowing it to escape.
  17. wheelsy

    wheelsy New Member

    maybe ill just wrap the part my leg is in contact with
  18. Simon_A

    Simon_A Member

    Mate, just do the whole thing, I picked up a couple of expansion chambers today. Last time I bought a roll of exhaust wrap there was enough for 2 sets of pipes with some spare.

    I will go ya halves if ya want.

    I also swapped the basic as bricks carby today for a pocketbike one. Straight swap fitment and it will run sweet. Swapable jets, proper adjustments, etc.
    Last edited: Jul 2, 2008
  19. fastboy9

    fastboy9 Member

    Sorry to go off topic, but where and what carb?? I've got a walbro at home but to get it on the bike is way more than just a straight swap fitment.

    To get the most out of these engines a carb uprgrade is essential. The top speed bogging is really starting to annoy me now! The jets are too small, and for the expansion chamber to work at its best then I have to get more fuel in there!

  20. Simon_A

    Simon_A Member

    Okay, pretty much all watercooled pocketbikes run a chinese clone of the Dell'orto SHA carb.

    Mines a genuine one but the chinese clones are identical.

    They are a direct swap part for the horrible stock carb that comes with the happy time.

    But you have all the usual adjustments found on a normal carby. And to adjust the mix you just take the 2 screws out of the bottom of the carb and there are screw in jets, standard Dell'orto jets are used and they fit in the chinese clones too.

    As the shots show, its childs play to put a proper carby on these engines.

    Here's a clone on eBay

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    Last edited: Jul 2, 2008