How do you do the cut muffler mod?

Discussion in 'Performance Mods' started by Corey, Jul 2, 2011.

  1. Corey

    Corey New Member

    Hey, i've heard about a mod which involves cutting the muffler or baffle in someway (I dont know im only new). It sounds way better and has more power/speed, anyone know how to do this mod? and does it use more fuel/decrease life span of engine?
    All answers appreciated,

  2. adrian101

    adrian101 Member

    Last edited: Jul 2, 2011
  3. Corey

    Corey New Member

    Thanks heaps ill have a look :)
  4. adrian101

    adrian101 Member

    this may help more:

    If you have the exhaust with the nut on the bottom then un-screw it and you can gain access that way. The one with the nut on the bottom does NOT have the baffle crushed nor the holes in the baffle like the one in the video above thou you can still cut it the same way he is doing so. It is basically a guild that does improve performance.

    hope that helps. Good luck
  5. motorpsycho

    motorpsycho Active Member

    this is a bad video because he concentrates more on porting the intake manifold and the flange on the pipe. his muffler mod isn't anything special and he really doesn't show how to do it. he just tells you what he did.
    as for the performance gain on his bike...i doubt that it made a huge difference.
  6. motorpsycho

    motorpsycho Active Member

    yeah this video is better but the guy is a total hack. using a pry bar as a hammer, and not putting the screws back into the muffler end cap.
    I did a mod similar to this one, but mine isn't as loud as his.
    he also didn't mention pulling out the catylist that up inside the muffler by the head tube. the catylist (or catyletic converter) is nothing more than a peice of steel pipe, with corrugated steel rolled up inside of it. this will clog up with oil over time and you will lose a ton of power. pull the catylist out of the muffler and leave it out.

    I retain the baffle pipe (the one with the holes in it) and the flat baffle plate.
    I drilled 3 small extra holes in the flat plate attached to the baffle pipe.
    cutting off the baffle plate and tube will make a lot of noise. mine is louder than stock but not as loud as this guys.
    also, i slid my end cap up inside of the muffler body, drilled 3 holes and attached it with 3 rivits. this way the pipe looks like a big open straight pipe, but it retains the baffle.
    first off, you need this style of short muffler to modify it easily.some of the newer style mufflers are all welded together. the older style ones (like the one pictured) are held together with screws. if you have a newer one that is all welded, you will have to cut it all apart to get the guts out of it. then you will have to weld it back together. my muffler is from 2009, and i'm sure that some engine kits still have this style of muffler. I'm not sure which kits come with the newer style muffler that's all welded together.

    this is a long pipe and i had to modify it up by the flange to make it longer for crank clearance. here you can see the internal parts all laid out (except for the catylist which is pictured later.) along with a stock short pipe and internals.

    here's the stock baffle and plate that came out of my muffler. the one in the long pipe is the same as the one from the stock short pipe. the long pipe did not have the catylist inside of it.

    here's how i modified the baffle plate. drilled 2 small holes in it. this allows me to retain the actual baffle and it's not nearly as loud as when you cut the baffle off. the 2 small holes open up the restriction of the baffle plate and give the exhaust more flow. these engines don't give off a lot of exhaust or a lot of pressure, so 2 small holes will help a lot. you could drill more than 2 but it may make it even louder. if sound isn't an issue, then i suppose you could drill more holes. I like to keep the baffle and plate all attached because they give you some back pressure. i'm afraid that by completely cutting them off, you will lose a lot of backpressure (which is needed). i also cut off the small pipe that sticks out of the end of the muffler end cap. they usually end up coming lose after awhile anyway.

    not shown in the other pics, or in any of the videos listed is the catylist. this is located up inside the muffler body by the head pipe. it's held in the muffler body with one screw on the older style pipes. if you have the older style pipe like shown here and in the videos, this will come right out when you take out the single screw n the outside of the muffler body up by the head pipe. my suggestion is to take this out, and leave it's a huge restriction, and it will get clogged up with oil over time. I'm not even sure that it actually does anything, other than collect oil and get clogged up.
    i'm not sure how this part is held into the newer welded together style mufflers.

    here's how the end of my muffler looks. I cut the end of the muffler body at an angle just for looks. then i put the baffle and end cap up inside of the muffler body. I drilled 3 holes through the outside of the muffler body and into the muffler end cap. i used pop rivits to secure the baffle and end cap to the muffler body to hide it. this makes it appear to be a big open pipe with no baffle. I painted the inside of the muffler body and the end cap black to hide it even more.
    here's the pipe and muffler on the bike.

    here's a pic. of the same idea, just on a different muffler that i modified. this allows you to see the end cap and baffle up inside the muffler body to see where it's at. I painted the inside of the muffler body and the end cap black after this pic. to hide it even more.

    seriously you will notice a performance change, but not a huge one.
    if you are looking to gain a little power on the cheap, then this is the way to do it. If you want a lot more power, then you shoudl go to an expansion chamber pipe.
    I put an expansion chamber on my little 50 c.c. 2 stroke and got a big change in power.
    i used a chamber from spooky tooth and i made a muffler for it out of the stock muffler.

    here's the spooky tooth expansion chamber. i added a 5 inch section of straight pipe between the chamber and the modified muffler that you can see right under the cranks.

    i added a chrome turn out to the end of the muffler to keep oil from getting blown onto my rear tire.


    the spooky tooth expasion chamber is short and it only has about a 1/2 inch stub pipe at the end of it, which makes it tough to add a muffler. I added the extra peice of straightpipe between the chamber and the muffler to get the muffler back away from the pedals. I welded the pipe to the chamber, and welded the muffler to the pipe. in this case, welding ir brazing is a must...j.b. weld or pop rivits won't cut it. (i did dress and smooth the welds with j.b. weld to hide them, and i painted the j.b. weld siver so it blends in.)
    your exhaust needs to be welded up so there aren't any leaks. leaks equal a loss in power, and more noise.
    this pipe and muffler are actually quieter than the stock modified pipe. i did the same baffle mod to this one as i did to the other one, and it's quieter, but makes more power.
    Last edited: Jul 2, 2011
  7. jaguar

    jaguar Well-Known Member

    Just as important as unrestricting the baffle is the distance from the piston to where the pipe first opens up and lets the gases expand. That's where a negative pressure wave reflects back to the cylinder, helping pull out the last of the exhaust gases and helping pull in more air/fuel charge into the cylinder. The distance relates to the powerband. See my post in Wild In The Streets entitled "Pipe mods for low end power".