Exhaust Muffler help

Discussion in '2-Stroke Engines' started by jtmiyake, Jun 2, 2009.

  1. jtmiyake

    jtmiyake Member

    Hello. I have had a few posts on this subject. My first one was about the horrible rattle in my muffler. Seems the internals came apart and the bike got a lot louder. So I then researched muffler options. I ended up purchasing the HUSH cat muffler from Zoom.

    Installed this new muffler yesterday. I have to say it is much quieter now. Not sure if quiter than stock but quieter than my broken up muffler. I seem to have a problem thou. It seems there is so much restriction in this muffler that I have now completely lost power and upper rpms. I can barely get the bike to 20mph and can hardly climb a slight incline.

    In addition, this muffler runs supper hot as one might expect with a catalytic converter built into it. After a 5-minute ride it was already burning the paint off the muffler. Something seemed wrong so I brought back home to determine what to do next.

    Any suggestions? I am thinking I will let it cool down and open it up. This one looks like it can be opened as there is a bolt on the end and appears to be a flange on the bottom.

  2. s_beaudry

    s_beaudry Member

    The simple fix I am thinking...

    See if you can take it apart and drill some small ( ~1/4" ) holes in the baffle to allow for easier flow.

    The downside to this is drill slowly as the more holes you add, you will gain back the lost power and it will start to get louder with the less baffling.

    This should solve the overheating problem as well...
  3. loquin

    loquin Active Member

    what kind of motor is it on?

    A catalytic converter burns the excess fuel in the exhaust, so, if you're running rich, your converter can get very hot...
    Last edited: Jun 2, 2009
  4. jtmiyake

    jtmiyake Member

    It is a 66cc 2-stroke engine. I pulled the spark plug. A little black but not bad so a little on the rich side.

    s_beaudry - I can definitely see the existing holes and these are the locations where the paint is burned off on the outside. I guess it is trial and error with one hole at a time?

    It still seems odd that it would cause that much of a change in performance.
  5. s_beaudry

    s_beaudry Member

    Someone correct me if I am wrong here...

    But my understanding of a 2 stroke engine is that for it to run properly and smoothly, it is dependant on the correct amount of backpressure from the exhaust.

    Too little is a bad thing, and too much is a bad thing too!
  6. jtmiyake

    jtmiyake Member

    Here is what I learned today. I contacted Zoom about this muffler. They stated...

    "Due to EPA regulations, the power of the engine must be restricted as to
    keep the bicycle at a "reasonable" speed. If you visit our forums at
    www.zoombicycles.com you will find plenty of information related to
    increasing the flow with these mufflers. It's really quite simple - the
    easiest method being to drill a 3/8" hole straight through the side of the
    muffler (near the bottom), through to the other side."

    Then I found this thread on their forum but has been locked


    My engine barely ran with this muffler on so I had to switch it back to my rattle can muffler. I began checking out the new problem muffler. There are pictures attached where you can see where the exhaust blows out the holes into the larger chamber. This is where it the paint burned off. There are 4 1/8-inch holes. So it would seem to me the best way to fix this muffler is to drill out one or two of them. I decided to drill out two of them to 1/4-inch.

    The problem now is I have two holes on the outer sleeve and these will blow onto my leg. I think I'll look for a moderate thickness piece of metal plate that I can wrap around the holes and then hose clamp the thing together. I have braising equipment but I think I need to find a high temp solder to seal it all up. I guess I can post up on Craig's list for a quicky weld job.

    Regardless... what a pain in the @ss. Buyers beware....

    Update.... I ended up drilling all 4 holes to 1/4-inch. I used a food can to wrap around the pipe, then sealed with this handy wrap repair kit. The patch becomes a part of the metal after heating up. I finally wrapped the entire pipe with exhaust wrap.

    Attached Files:

    Last edited: Jun 3, 2009
  7. jtmiyake

    jtmiyake Member

    You are correct, there needs to be a certain amount of backpressure. That is why I quickly stopped my ride because it did not seem right. I know others cut baffles out but I suspect this will decrease longevity of the engine.
  8. jtmiyake

    jtmiyake Member

    Last update

    Seems I just wasted a bunch on money on it and then trying to mod it. After a ride of the exhaust smoking like *ell and still no power I gave up today and switched back to my old loud rattle can muffler. Nothing more to say...:censored::censored:
    Last edited: Jun 3, 2009
  9. danlandberg

    danlandberg Member

    I don't no how much $$$ a cat muffler is, have you looked into a expansion chamber?
  10. angrysamoan

    angrysamoan New Member

    Hey Bro, Hoz it goin? I now have four two strokers. Two 48cc and two 66cc, Point is- I.ve drilled 1/8" holes in all the exhausts of these bikes. At first I drilled larger holes on the end of the pipe- lose of back pressure and to loud. Found perfect to drill about {4} 1/8" holes around perimeter at end of pipe, Good Luck. Got more speed and not to loud.