Exhaust Modification

Discussion in '2-Stroke Engines' started by Timbone, May 25, 2014.

  1. Timbone

    Timbone Active Member

    I did a recent exhaust mod that I think you will find interesting!

    I attached a 2 1/2 foot stretch of heater hose (got it from autozone) to the stock muffler, snaked it up through the center of the back triangle and out over the top of the back tire. Then I attached a small lawnmower muffler to the end. I made a little chain out of 3 small s-clips to keep it nicely suspended from the saddle.

    The motor is still loud since there is still plenty of gear chatter and intake noise. But the general sound is much more motorcyclish. Nice purr at idle. And I have more overall speed. Before the mod, the sweet spot was 24-27mph. Now the bike will run nicely at 27-32mph. I don't run WOT.

    I am also still working on my own spring loaded tensioner that can be made on the cheap. If I can perfect that, I may offer some to others at a very reasonable cost.

    MPH is being measured by a cheap bike speedometer I bought at WallyWorld. Funny thing: during certain run ups, the magneto seems to wind up enough of an electrical field to disrupt and reset the speedometer.


  2. HeadSmess

    HeadSmess Well-Known Member

    yes, the ignition will mess with any electronic device near it... took me a while to figure out why my LED light was turning on by itself and going flat whilst sitting in the bar bag...

    tis called EMR :) mount the coil further back.
  3. Fabian

    Fabian Well-Known Member

    So that's why some of my LED lights mysteriously turn themselves to different modes or turn themselves off. Interesting.
  4. HeadSmess

    HeadSmess Well-Known Member

    pretty sure its all from the plug gap itself, so the only cures are resistors...R series plugs, resistor cap, resistive leads... or space.


    while they sound good in theory, spring tensioners...are not! compression braking and starting requires one really strong spring, or a limiter of some type that just defeats the purpose.

    P.P.S. take at least a link out of your chain ;) loose as a goose... mmm, mongoose...
  5. Timbone

    Timbone Active Member

    I WANT to take a link out of the moto chain but with the rear wheel set as it is - and it has told me where it wants to be! - I do not have enough slack to remove an entire link. I am surprised by this, too.

    Really, I have this thing in the sweet spot. It's rolling good. Wheel and rear drive sprocket are true. Chain seems loose but it is threading nicely with no issues. I m not changing anything until I have to!

    This is my learning bike. On the next one, the chain tensioner will be on the pedal side. I'll let the moto chain tell me where the rear wheel shall go.


    P.S. Since I have been riding my moto for short errands, the MPH on my car has jumped from about 28.6 mph to 31.6. Another benefit of the motorbike!
  6. bluegoatwoods

    bluegoatwoods Well-Known Member

    This looks like a great exhaust modification. Are we talking about rubber heater hose? Something that would run up to the heater coil in the firewall in a car, for instance?

    Good job. And thanks for sharing. 'Cause if I can imitate that, then I'm gonna give it a try.
  7. Fabian

    Fabian Well-Known Member

    A recipe for disaster; with all of the ingredients needed to the bake the perfect catastrophe.
  8. Timbone

    Timbone Active Member

    Yes, it is the thick rubber "Heater Hose", and 1/2 inch ID fits very well on the kit muffler with a hose clamp. I have ridden a few tanks of gas on this configuration and it seems to be doing fine. Only time I smell exhaust now is when I am sitting at idle w a tailwind.

    Got the lawnmower muffler at Lowe's for about $6. It has a 3/4 inch male thread so I had to find an adapter to get from the 1/2 inch ID of the heater hose to the 3/4" muffler. A bit of JB Weld just to be safe.

    The rear muffler doesn't get very hot - just oily. :)

  9. Timbone

    Timbone Active Member

    Isn't this part of the problem? How do you know when things are as good as they will be? I worked through my problems of getting the sprocket to stay true. Solved the problem that kept moving my wheel little by little in the frame. There are no funny noises. Chain just rolls right over and through the chain tensioner like magic. Engine seems to be getting better. So far so good.
  10. butre

    butre Well-Known Member

    if you move your tensioner away from the sprocket about an inch you should have enough slack to pull another link out
  11. HeadSmess

    HeadSmess Well-Known Member

    other option ive resorted to for no tensioner systems is to grind the rear engine spacer where it snugs up to the engine...

    better place to locate the tensioner in my mind. shimming out with plates to compensate for wear etc... never loosen up at least :)
  12. butre

    butre Well-Known Member

    In my opinion, those springy tensioners that mount to the output sprocket cover puts the tensioner in the best spot, requires the least adjustment, and is considerably safer than the stock pile of garbage that clamps to the chain stay for about 50 miles before it smacks into the spokes and leaves you stranded.