exhaust - to chop or not to chop?

Discussion in 'Performance Mods' started by spbwsean, May 27, 2009.

  1. spbwsean

    spbwsean Member

    on my latest build I chopped my exhaust and ran with about 7 inches of 7/8 tube with a couple small bends.....it was loud and did 50km/hr
    today I took my custom exhaust off and swapped it with the stock exhaust(my homemade/chopped/custom exhaust was blowing burnt oil onto my shoes when i rode and i wear white snealers! lol)
    anyways with the stock exhaust I am only getting 35km/hr.........**** of a lot quieter and white shoe friendly

    any comments etc? anyone else chop their exhaust and notice performance changes?!?!
    Last edited: May 27, 2009

  2. wilbur

    wilbur Member

    Where did you get your kit from?.
  3. Stink Bike

    Stink Bike Member

    I cut about 1 inch off my exhaust and all it did was make more noise.There was no improvement in performance.
  4. spbwsean

    spbwsean Member

    wilbur - my motor is a powkerking from zoom
  5. fourfeathers

    fourfeathers Member

    Hi greetings from Fourfeathers in Newzealand.
    Yes I've not only chopped but also modified the stock exhaust on my 70cc. This is what I've done after experimenting for about a year now. I cut off the inturnal baffle pipe right back to the end cap then ground the rest back down to the inside of the cap then completely removed all the baffle plates. The piece of pipe on the outside of the end cap I bored out by about .5 of a mill. Now you need a piece of stainless steel tubing the right size so you can sweat it on over the remaining pipe on the out side. This is called a stinger tail pipe which acts like a pressure release valve and is responsible for creating the back pressure needed. The stingers' length should be 10 - 12 times its' inturnal diameter. I have cut mine to 11 times its' diameter because that suits the terain I ride over. My cruising speed is usually around 40 -45KPH and I can easily push it up to 54.6 with out any trouble on the flat with no tail wind and climb inclines of 1 in 4 at 35 -38. In fact it will accelerate up hills on its' own accord. The expanssion acts as sound box reflecting the sound waves from the exhaust port back into the engine as the piston gose down drawing in a fresk load of air/fuel mix from the inlet side this ,in effect, super charges the engine. This has more more affect on my motor as I've made extensive mods to my carby, I have done this proceedure on a 49cc with the same effect. Dispite what people say it dosen't harm the engine I've checked and double checked and I've done 2000Ks and everything is A OK. All engines need to breath properly to function at thier optimum. Have fun, you wont regret it.
  6. Marz55

    Marz55 New Member

    Where do you buy whizzer batteries in Ohio?

  7. spbwsean

    spbwsean Member

    thanks fourfeathers

    thanks for your post/reply fourfeathers.........I think i will try your technique, sounds good. I will post my results

    BTW any chance of seeing a pic or 2 or your mod?
    thanks again & cheers