Discussion in '2-Stroke Engines' started by geebt48cc, Feb 13, 2010.

  1. geebt48cc

    geebt48cc Member

    Here I am again, So, with stock muffler, what can I do to help it breath better? Drilling out, does that help that much? + if so, where's the best place to drill?

  2. AussieSteve

    AussieSteve Active Member

    You should really have posted this in the appropriate 2/4-stroke engines section, for the best answers. I'll assume that you have a 2-stroke HT.
    I got a very slight power increase without much extra noise by drilling two 4.5mm holes right through the stinger about 1" - 1.5" inside the end cap and before the baffle plate.
    This allows a small amount of exhaust gas to bypass the baffle, allowing slightly better flow without substantially reducing back-pressure. I didn't want to go too far, hence only 2 x 4.5mm holes.

    ... Steve
  3. motorpsycho

    motorpsycho Active Member

    If you have a h.t. 2 stroke, with the older style muffler (this is a muffler held together with screws). take the 3 screws out, and take the muffler apart. This will take some work because these mufflers are fit together very tightly. I used a long brass rod, inserd into the muffler against the baffle plate, and i hit it with a hammer to get it apart.
    Inside you will find a catalyst, which is a peice of pipe about the same diameter as the muffler, and it has corrugated steel inside of it. Take this peice out and leave it out. I'm guessing that this peice is for emissions, but in reality it's a cork in the exhaust flow. This peice is located at the end of the muffler, closest to the motor and is held in the muffler with one of the screws through the side of the muffler body that I said to remove in the beginning.
    when you get the muffler apart, you will find the baffle (a skinny pipe with random holes in it) and a baffle plate (welded to the skinny pipe with the holes in it). notice the baffle plate...look at is closely. you will find that there is ONE TINY hole in it for exhaust to get through. I was surprised wen i found this because i have no idea how exhaust even got through this hole. on my muffler, it looked like a hole made by burning through the plate while doing a very bad weld. the plate fits in the muffler body VERY tight, so exhaust can not flow around will only flow through a hole(s) in the plate.
    here's what i did...i drilled 3 small holes in the plate on the opposite side of the baffle that the exhaust exit is on the muffler cap. This way, the exhaust can flow, but it will have to go through the baffle before it exits the muffler. This keep the sound fairly close to stock, but allows the muffler to flow ALOT better. I'm running this muffler on the end of an expansion chamber, and it's only a little bit louder than stock, and it sounds very healthy.
    If I were you, and you are concerned about exhaust flow...get an expansion chamber, and then modify your stock muffler to go on the end of the chamber. An expansion chamber will give you more power, and a better sound. You can even get an aftermarket stinger (muffler) to go on the expansion chamber so you don't have to go through all the trouble of modifying your stock muffler if you don't want to.
    drilling a hole or holes in the muffler body itself will only increase the noise. It will not do much for the flow. My friend drilled holes in his muffler body. He started with one hole and drilled others after test riding it every time he drilled a hole. the only difference there was, was that it got louder. the engine did not gain any power.
    Last edited: Feb 14, 2010
  4. geebt48cc

    geebt48cc Member

    Nope, I just got this 12/10/09.................It's one piece muffler................Yes, there's a bolt in the bottom, but it doesn't open it up.
  5. geebt48cc

    geebt48cc Member

    48cc Skyhawk Muffler

    :helmet:Does anybody know if a (Dec. of last yr) factory flat black muffler"

    Last edited: Jun 27, 2010
  6. KCvale

    KCvale Motorized Bicycle Vendor

    All the Grubee tailpipes I get are black.
    What are you asking?
  7. geebt48cc

    geebt48cc Member

    fun 48cc

    Really enjoy 48cc big 1.95 HP

    Wonder what it does in 1/4 mile?

  8. KCvale

    KCvale Motorized Bicycle Vendor

    My Skyhawk 48cc can make 30MPH in about 100 yards, but I have a 3-speed Jackshaft shift kit on it ;-}
  9. geebt48cc

    geebt48cc Member

    Muffler with, or without?

    :veryangry:Hi HT friends,

    On 48cc Skyhawk 2/stoke

    1. When cap is taken off muffler, it runs fantastic, just loud.

    2.When I put cap back on (With two drilled holes) it really doesn't do that well at all?

    See, in reading, a 2/stroke needs a bit of back pressure to run right. (but when cap is taken all the way off, it does very well?
  10. professor

    professor Active Member

    As far as I know, any engine runs stronger with zero back pressure (as long as the mixture is set correctly that feeds the engine). No one at the drags wants back pressure affecting their engine.
    Removing the muffler can change the fuel mix (leaner), so if your engine was over rich to beging with- it will run stronger without the muff.

    Please do not annoy everyone by running without a muffler.
    You may want to adjust your carb jetting to work better with the stock muff or put twin mufflers on it (as seen here one this site), thus reducing back pressure.
  11. geebt48cc

    geebt48cc Member

    Thanks, I very much agree...............
  12. Alson

    Alson Member

    My friend wants to know if he can run his bike without the cap on the muffler, he wants to know if it will hurt his engine, I would think it would run a little leaner if he done that. Any wayl he wants a strait answer