Exhaust Cutting

Discussion in 'Performance Mods' started by JimKamenidis, Aug 24, 2010.

  1. JimKamenidis

    JimKamenidis Member

    Will it be better or worse for the performance of my 2-stroke if I completely removed the muffler and only kept on the pipe from the engine?
    (sound is no problem.)
    And really what is the best I can do with the stock muff for performance because I don't want to bother putting a new one on..
     

  2. motorpsycho

    motorpsycho Active Member

    uhh, don't totally remove the muffler. a straightpipe is not good for a 2 stroke.
    you can modify the stock muffler for good flow, and it will be a little louder than stock.
    if you can take your muffler apart (some are screwed together, some are welded). remove the muffler end cap.
    remove the catelitic device that's inside the muffler, all the way up at the top where the pipe goes into the muffler. (it's a small round peice of steel tube that's about the same diameter as the muffler and it has corrugated steel coiled up inside of it. if your muffler is screwed together, there will be one external screw holding this peice inside the muffler, and 2 external screws holding the end cap on.) Drill 1-2 small holes in the baffle plate (not the baffle pipe) that is welded to the inside of the muffler end cap.
    i have done this to 2 different stock mufflers and they work great.
    of corse, the BEST thing to do is chuck the stock pipe and muffler and get an expansion chamber with a muffler on it. a modified stock muffler works well on an expansion chamber, but it may not fit on some expansion chambers due to the way they are built and where the end of the pipe ends up.
    I am using a spookytooth exp. chamber with a modified stock muffler on one of my bikes and it made a big difference in performance.
     
  3. JimKamenidis

    JimKamenidis Member

    thanks but I thing my muffler is a bit different, the baffle in the end is held on by a screw and the whole muffler is held on the straight pipe with two screws and I think the catalyst is welded on the straight pipe :S
     
  4. GearNut

    GearNut Active Member

    That indeed sounds different. Could you post a picture?
     
  5. JimKamenidis

    JimKamenidis Member

    It seemsto be this one "http://ep.yimg.com/ca/I/yhst-10337746512064_2121_334105" and I have bought the engine from boygofast
     
  6. motorpsycho

    motorpsycho Active Member

    I got 2 engines from boygofast. one in august 2009 and one in july 2010.
    both of mine came with the muffler that is screwed together.
    trust me the catylist part is in the muffler, not in the pipe.
    even if your muffler is all welded together, i beleive that you can grind off the welds and get it apart. you could eaither use pop rivits to put it back together or just have it re-welded, but you will loose the chrome if you do that.
    seriously, your best bet is to get an expansion chamber and a stinger muffler.
    you will be much happier with the performance gain, and the sound is so much better than a stock muffler.
     
  7. JimKamenidis

    JimKamenidis Member

    I eventually will but for now can I just throw the end cap away..?
     
  8. motorpsycho

    motorpsycho Active Member

    the end cap has the baffle and baffle plate welded to it.
    without those, you will not have suffiecient back pressure, and it will the same as a straightpipe.
    I do know a guy who is running just a straightpipe (the same size pipe for the entire length of the exhaust) and his engine is very loud, but it does not have the same power that mine does.
    2 strokes need some back pressure from the exhaust to run "right". with the rotary valves (like all h.t. engines have) the backpressure helps fill the cylinder with the incoming air-fuel charge. without backpressure, some of the air-fuel charge can escape through the exhaust before it ever gets a chance to be compressed and burned.
     
  9. JimKamenidis

    JimKamenidis Member

    It seems you are right but I am really confused because one day my exhaust gasket somehow got cut-off and there was a big hole there and I noticed a huge performance increase! And I was wondering if a little hole like that could have such a difference in performance imagine what a big hole would do.. (but it was loud as ****)

    ..and about mid-way of my exhaust there is another plate that creates enough back-pressure I think..
     
    Last edited: Aug 25, 2010
  10. motorpsycho

    motorpsycho Active Member

    there is a difference between a good flowing exhaust and an open exhaust.
    you will get more power from an open exhaust but it isn't good to run it that way.
    you can run a muffler that has been modified for better flow, and it will still provide good backpressure.
    the only things that should be in the muffler is the catylist peice, a flat steel plate with a tube welded to it with holes drilled in it, which is welded to the end cap.

    here's what the end cap should look like when it is removed from the muffler.
    [​IMG]

    and here's what the catyletic peice looks like. i took mine out and threw it away (on both of my bikes)
    [​IMG]

    the cateletic peice is the same diameter as the muffler and it's located in the muffler at the opposite end of the end cap.
     
    Last edited: Aug 25, 2010
  11. JimKamenidis

    JimKamenidis Member

    problem found, my exhaust is copletely different :p
    anyway I cut the bolt for the end cap so there is no turning back now, I'll just do it by trial and error! thanks in return for all the kind help :)
     
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