Build or buy expansion chamber?

Discussion in 'Performance Mods' started by BikeBuilder43, Jul 10, 2016.

  1. BikeBuilder43

    BikeBuilder43 Member

    Hi guys. I am new to the idea of expansion chambers. I am thinking of building one but with very little knowledge I dont know if its a good idea. What materials should I use? How to connect the piping? Who sells the best expansion chambers? I dont care how loud it is. I live in the country.

  2. jaguar

    jaguar Well-Known Member

  3. HeadSmess

    HeadSmess Well-Known Member

    making one... i tried brazing one, but got really lazy and simply butted it together with the inevitable result that it fell apart. very quickly. my plan was to use aerosol cans, and leave tabs on the edges to do "lap" joins, which are far stronger. anyways, that was just an experiment. brazing can be a legitimate, fairly easy method to join it all up, but you gotta do it properly!

    every other pipe i have made i have welded, that is, about twenty pipes. in theory its quite simple, roll some 0.8-1mm steel into shaped cones, weld together, viola! attach!

    in practice its a beetch... hard to roll cones, hard to hold them in place when you tack them together, and you really need to make a few trial pipes from stiff paper to get the layout right. a LOT of work. it gets easier with practice, but still...if you aint experienced... have fun! theres a few programs you can download that will at least let you figure out the templates needed for each "segment", after having used some type of software (or plain number crunching) to figure out a good pipe design.

    its the way to do it if you want real definite results.

    no, i never bothered making the pipe in the aforementioned link. i did intend to, because i think its basically a joke, but i cant make head or tail of the "spreadsheet" layout. i wanted to test it against certain other pipes designed on software that does seem to produce results just so i could laugh, but yeah... anyways. thats another story. saying anything at this time is sheer conjecture :)

    if you havent/cant weld thin steel sheet, dont have a very good MIG or TIG welder, or oxy acetylene kit(welding thin steel is freakin HARD)... and cant figure out how to cut the templates from the steel, plus have a few tools in the workshop (sheet rolls, a bender,anvil or mandrel, that sort of thing,) buy a premade pipe. theres a few links to decent ones posted on here. do not waste time getting the "banana" pipe.
  4. BikeBuilder43

    BikeBuilder43 Member

    Thats a lot of good info. Was thinking of going with the banana pipe but now i'm not. I want a powerband in the higher rpm range. I dont know the do's and donts of porting but i matched my ports and lowered the intake port a good bit. Also bored out the transfers a bit and angled the top of the transfer ports so they are more exposed. I lost a bit of low end torque but it has a lot more upper mid-range power. It really pulls. I definitely need to regear it becaust it pulls all the way to top speed.
  5. Steve Best

    Steve Best Active Member

    It is possible to increase the powerband at all rpm with careful (and conservative) port work.
    Read over my past posts and pictures for detailed info, but in general:
    1) don't touch the vertical. A little mistake can be hard to live with.
    2) Widen the exhaust mainly at the top (near the head) of the window into the cylinder. "Vee" it into the bottom.
    3) widen the intake mainly at the bottom or the cylinder window. "Vee" it into the top.
    4) blend both ports to the manifold face removing the minimum amount of material. Keep both the original diameter.

    With a 3-5mm squish band (at 0.030") and some minimal attention to intake and exhaust length you will have an engine that will haul from 1000 to 10,000 rpm. It is possible to not give up any power anywhere in the rpm band. No reed, stock NT carb, no tuned pipe.

    Just imagine if I had a properly tuned pipe? Next week I hope.

  6. BikeBuilder43

    BikeBuilder43 Member

    I wish i knew dimensions and had the right tools to port. I got lucky with the port work i did. It has power where i want it, in the mid to upper rev range where i use it most. Just need a pipe to compliment it now.
  7. BikeBuilder43

    BikeBuilder43 Member

    Where can i find a 28t sprocket?
  8. BikeBuilder43

    BikeBuilder43 Member

  9. butre

    butre Well-Known Member

    Angel Cortez I'm told has done 28t for a manic mechanic adapter, or mzmiami has 28t rag joint adapters and disc brake sprockets
  10. BikeBuilder43

    BikeBuilder43 Member

    I did a 30t once. Loved the top end speed
  11. Steve Best

    Steve Best Active Member

    The tall handlebars and lack of front brake are bad ideas for a bike focused on speed.
    I was able to attain 66kph with 44t so I don't understand the need for a 28t.
    My experienced guess is that it will be a slug. Which is probably a good idea with no front brake.

    Edited - not proud of my original remark. Tired and grumpy. Sorry about that.

    Last edited: Jul 16, 2016
  12. BikeBuilder43

    BikeBuilder43 Member

    You lost me. Lol
  13. mrbg

    mrbg Member

    I could never understand the apehangers, I can't see how they could be comfortable on Long ride
  14. BikeBuilder43

    BikeBuilder43 Member

    I've had apehangers before and its not bad. I always go on long rides. Used to drive 14 miles both ways to work every day. I got these tall ones more as a head turner than anything. Lol
  15. Frankfort MB's

    Frankfort MB's Well-Known Member

    I think the motorized bicycle accomplished that:);)
  16. BikeBuilder43

    BikeBuilder43 Member

    Oh it has but I am taking it to the next level. Lol Now i want to build some extended forks to give it a "chopper" look
  17. Frankfort MB's

    Frankfort MB's Well-Known Member

    You also could use a MZMIAMIPARTS exhaust

    They have power at the top of the rpm range, they also very loud and very cool looking (in my opinion)
  18. BikeBuilder43

    BikeBuilder43 Member

    I actually went on that site yesterday and have been thinking about it ever since. Is the power increase worth the price?
  19. BikeBuilder43

    BikeBuilder43 Member

    I know i will see good gains with the port work i have done. Like i said, i got lucky with the porting. I looked at the ported jug on one of the sites and tried to mimik it. It was fun and the extra pull in the mid range was a plus. I also shaved a semi-circle into the bottom of the piston to match the port at tdc
  20. Frankfort MB's

    Frankfort MB's Well-Known Member

    I think got an increase of about 5mph ish

    It has noticeable top end boost but the bottom end is a little less.... (I am used to no baffled stock exhaust)

    It is kinda heavy too so it needs some mounts made for the back. I just ran the exhaust studs and they wouldn't hold it without major vibration

    I recommend for a cheaper substitute of the SBP expansion chamber