Muffler for 4 stroke engine.

Discussion in 'Spare Parts, Tools & Product Developement' started by louturks, Nov 29, 2007.

  1. louturks

    louturks Guest

    Is there a place that sells a muffler for a 4 stroke engine that would make a noticeable difference in the loudness?

  2. gone_fishin

    gone_fishin Guest

  3. louturks

    louturks Guest

    Okay augidog, thanks
  4. gone_fishin

    gone_fishin Guest


    btw-you'll have to be way more specific about what kind of engine? and what kind of difference in sound level, too?
  5. louturks

    louturks Guest

    Well it's a Bridgestone 2.5 hp 4 stroke. I wanted to see if some company sells a muffler that would deaden the sound some.
  6. Alaskavan

    Alaskavan Guest

    I am shortly going to be working on the muffler situation for my project. As I see it, the options are to purchase a muffler designed for a motorcycle (too loud), an ATV (a possibility), a small car (another possibility) or building one myself. I've been studying the design of commercial mufflers, but am still undecided.
  7. louturks

    louturks Guest

    Hey Alaskavan, that's neat, I hope you come up with something good. I seen that the bicycles at Spooky Tooth have a muffler coming from their motors. I don't know how much that quiets the sound. I also found this on I don't know if this would fit all 4 stroke engines
  8. Alaskavan

    Alaskavan Guest

    I don't know anything about your Bridgestone motor. You will want to measure the port size and bolt spacing, and check with whoever you buy a pipe and muffler from to make sure it will fit. As far as the noise level for the mufflers sold for use with the 50cc 4-strokes (which may be about the right size for you), find a thread where somone has built their bike with a 4-stroke and ask them. They might also be able to tell you about pipe diameter and bolt spacing, too.
  9. louturks

    louturks Guest

    Okay Alaskavan, I'll do some searching
  10. An idea I had for quieting things down. Every motocross rider out there is totally convinced that their stock muffler/silencer/expansion pipe is junk and the fancy aftermarket one will give them huge HP gains. Truth is it is usually a slight increase in high end HP at the expense of low end torque. Some guys buy one after market silencer then another when the next great thing comes along. Regardless, my point is there are 2 or 3 used mufflers for every bike out there. Even the stock ones are beautifully made ovalized alumiunm with billet tips, super high performance. My thought is to use the stock muffler that comes with my 49cc motorbike (cause I figure it probably creates the appropriate back pressure, could be totally wrong though) then attach a much bigger bore pipe and silencer for a much bigger engine, say a 250cc. The second silencer should be big enough to not restrict flow but still decrease sound to some degree. Of course I'll wonder if it would be faster without the original muffler and end up experimenting. You 2 stroke guys should look into adapting motocross expansion pipes because, again, there's 2 totally high performance pipes out there for every bike ever made. I want to start a thread on this idea when I actually start doing it. If you search ebay, there's tons, you could of course just use one from a 50cc.

    Another thing to do is wrap the whole exhaust system with header tape. It's fiberglass strapping about 2" wide which contains heat and helps with noise too. As you are wrapping overlap by 50% so there is 2 layers. Hold it in place with bailing wire or stainless steele zip ties. Paint it black with silicone paint. You'd expect it looks ugly but it actually looks kind of cool, high performance race style. It's on ebay too or summit racing.
    Last edited by a moderator: Nov 30, 2007
  11. Alaskavan

    Alaskavan Guest

    I don't know about Lou, but I don't want mine to sound like a motocross bike. Even a stock one. I want mine to sound like a new Toyota Prius, sitting at a light.
  12. louturks

    louturks Guest

    Alaskavan, yea, that would be nice. Quiet
  13. Douglas65

    Douglas65 Guest

    Just an idea for making your own muffler, put a thin walled pipe with lots of holes drilled in it inside of a larger pipe and fill the space between with fiberglass or steel wool to soak up the sound. If you have access to welding equipment, or a high school shop class that needs a project, you are in business.

    To make it even quieter, place some restrictions in the inside pipe to force the exhaust to go through the wool between pipes.

    Simple really if you are ambitious enough.

    Also, you could check fleet/farm type stores for small tractor mufflers.
  14. Believe it or not the muffler on a dirt bike cuts the sound down a lot, you wouldn't think so by how loud they are but its true. I definitely don't want my MB to sound like one either and it wouldn't with the plan I had mentioned:
    1. Keep the stock exhaust pipe and muffler in place but add on...
    2. A larger pipe and motorcycle muffler as well (2 mufflers total).
    3. This shouldn't add much more restriction. It couldn't possibly make your exhaust louder and by all means should make it quieter. It will not come out sounding like a CR500, that I guarantee.
    The typical dirt bike muffler is basically a tube within a bigger tube. The inner tube is a through pipe (no real restriction) but it has hundreds of holes or is made out of mesh. The space between the two tubes is filled with fiberglass packing. Sound waves reverberate between the tubes, running into each other, cancelling each other out, being absorbed by the tubes and the packing. They do absorb sound but the with the higher priority being to not restrict flow.
    While we are on the subject, does anybody have any experience with this product? "Benz silent rider" or stealth muffler. This is where I came up with the idea above. I'd love to cut one in half and find out just what is going on in there. Or if we could find out the patent number I could do a patent search and get the drawings for it. Kind of pricey at $150-200.
    Anyway, it will be a few months before I report back on actual results.
  15. Alaskavan

    Alaskavan Guest

    KeepOn, thanks for the link. That's just the sort of thing I'm looking for.
  16. Quote from Kolpin:
    "The ATV Stealth Exhaust System fits on any ATV with a four-stroke engine to quiet ATV noise by 50% or more. It can be easily installed according to user preference and rear-of-machine configuration.Engineered with an innovative high-flow, low-restriction spark-arresting muffler, the Stealth Exhaust System quiets ATV noise by 50% without sacrificing engine performance. The patented design is used on military ATVs by both U.S. and British Special Forces, is also a USDA Forest Service Approved Spark Arrester.

    The ATV Stealth Exhaust System includes an efficient, aluminized steel muffler measuring 22 inches in length and 4½ inches in diameter. Fully welded, the muffler is proven to work well on all sizes of ATVs from 250s to 700s. The system comes complete with a universal kit including mounting hardware and detailed instructions for quick, easy installation; a universal adaptor elbow for high mount installations; a zinc-plated two piece wrap-around clamp hanger assembly; and galvanized flex tubing that turns the exhaust and noise closer to the ground.

    The ATV Stealth Exhaust System reduces noise levels for decreased disturbance of other public land user groups, and provides added protection to the environment through the use of a second spark arrester. Its revolutionary design results in less disruption of wildlife for the benefit of outdoor enthusiasts, as well as livestock for farmers and ranchers that use ATVs. In addition to significant noise reduction, the ATV Stealth Exhaust System actually delivers an increase in mid-range power and overall performance on some models, according to extensive dynamometer tests.

    How Does it Work?

    THE MUFFLER. We start with an extremely efficient, super quiet, high flow, USDA Approved, spark arresting muffler that is manufactured from high quality, aluminized steel to our specifications, exclusively for our patented ATV Sealth Exhaust System. The muffler is 22 inches long, including the outlet, and 4½ inches in diameter. It is not just a straight through silencer and it has no packing material that requires maintenance. It is a fully welded, USDA Approved, spark arresting muffler designed with a series of tubes and chambers. It has been tested and proven to work well on all sizes of ATVs from 250s to 700s."
    It's got me thinking.
    Last edited by a moderator: Dec 15, 2015
  17. Car muffler would be the ultimate for quiet and since they are often designed for engines
    many times our engines size they would offer practically no restriction to exhaust flow....tricky part tho is making a pipe to join the exhaust outlet of our engines to the inlet of the car muffler....oh...of course the car muffler is a little bigger than we are used to on our bikes.
  18. louturks

    louturks Guest

    I always wondered why they couldn't quiet gas operated weed eaters, lawnmowers, leaf blowers. Why when you operated one the whole neighborhood should have to hear it. I guess there must be more to it than what I think. But since we're discussing it on a bicycle, if someone sold a good muffler you can add on to a 4 stroke motor that would muffle the sound, you would think they can make some good money selling that
  19. prism

    prism Guest


    1) Muffler performance is a function of construction, back pressure, and size - and you can usually get two out of three. In the case of small power tools, the designer usually figures something like "as small as possible without excessive noise(?) or back pressure" - and what determines excessive noise is usually (half-baked guess) a legal issue. (This varies, most likely, depending on where the equipment is sold.)

    2) I myself have wondered about noise issues (as in I do not want undesired attention when using an engine) - and I wish to minimize back pressure (in hopes of less fuel consumption). I suspect that means a *large* muffler - like this:

    Attached Files:

  20. Alaskavan

    Alaskavan Guest

    Right now I'm leaning towards taking a small car muffler, cutting it open, stuffing the central chamber with glass or steel wool, and welding it back together. As Andy points out, it is designed for an engine many times larger, the additional back-pressure created by the dampening material shouldn't effect performance much.