Build or buy expansion chamber?

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

  1. jaguar

    jaguar Well-Known Member

    If you want to make sure it doesn't move from the new position you can buy a woodruff key 1mm wider and grind it down accordingly.
    But run it as is for a while and then take it apart and see if it has moved.
     

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  2. BikeBuilder43

    BikeBuilder43 Member

    Will do. That was the best thing i have done so far. It runs so much better. I even have more torque from a slow roll not even under WOT which i wasnt expecting. You really know your stuff man. Gotta love this hobby. The inner kid in me is living his dream.
     
  3. jaguar

    jaguar Well-Known Member

    I literally spent a year studying and experimenting with my engine for 2 reasons.
    1. to make my engine more powerful without sacrificing reliability
    2. just to learn everything about 2 strokes. I'd always been into 2 strokes before but mostly just riding, nothing of the engineering principles.
     
  4. BikeBuilder43

    BikeBuilder43 Member

    Your knoledge is valuable to us all. I am lucky to have people that are willing to share what they know. Now i need to go hunt down the best spark plug i can find then the exhaust
     
  5. Andy Birch

    Andy Birch New Member

    Guys, does the expansion pipe off a CR80 motocross bike work well with these little 80cc (66cc) engines? Are they as good as any specially made expansion pipe for our bikes? Screenshot_20161214-135253.jpg
     
  6. butre

    butre Well-Known Member

    yes, they do work well, but adapting it is a pain.
     
  7. Street Ryderz

    Street Ryderz Active Member

    Idk why so many people want top end only pipes when these engines benefit the most from bottomend and midrange improvements, witch enable it to turn lower gear ratios and still get up to its topend where the rpm is now making power!
     
    2StrokeMama likes this.
  8. Jonj57

    Jonj57 Active Member

    They work well with a shift kit, keep in that power band and you flyyyyyyyy
     
  9. Street Ryderz

    Street Ryderz Active Member

    If your power band is at the top of rpm range that means your running at wot to use it!
     
  10. Jonj57

    Jonj57 Active Member

    Power ban is mid to high and with a 7 speed jackshaft you can stay there the whole time then settle at half throttle for 35mph cruise. Either way wot is the way I like to ride these things most of the time. If it gets busted 109 and some labor and I'm back on the road. Still 3000 miles deep into my motor and she doesnt look like she's quitting yet
     
  11. Street Ryderz

    Street Ryderz Active Member

    The power band is determined by the pipe and porting not the shift kit!And a pipe that works at the top rpm isnt really the best for many reasons!If your pipe comes on in the midrange then its helping the engine to reach its topend by making the power to overcome the gearing!
     
  12. Jonj57

    Jonj57 Active Member

    You're right about the powerband, but the shift kit keeps you in your prefered RPM range so if you set it medium to high range you can keep on the band thru the gear range with the exception of low speed cruising/take offs, but even then I have more than enough power to start from a dead stop. Reed valve and boost port let you use the low end like it's a tractor.
     
  13. jaguar

    jaguar Well-Known Member

    I'm not a fan of loud motocross pipes on these engines.
    consider that they only have a 2000 RPM powerband and they lessen power before it comes "on the pipe".
     
  14. Jonj57

    Jonj57 Active Member

    While not absurdly stealthy I use a pipe adapter and some hose clamps to attach the standard muffler to the pipe and it brings down the sound a lot! Not sure if it takes a significant performance hit but it's worth bringing the sound down to almost moped levels
     
  15. BikeBuilder43

    BikeBuilder43 Member

    I have the thrust racing muffler. I've been noticing a loss of power and realized I had some exhaust leaks. I used a 2 part putty that hardens. It has the consistency of play dough at first then hardens enough to grind on. I filled in the leaks and partially closed off the stinger. It is now a little smaller then the header pipe and I saw a noticeable difference in mid range torque. I also picked up about 2mph on my top end. Has anyone else tried this?
     
  16. Jonj57

    Jonj57 Active Member

    Means you had too little back pressure and you brought it closer to in-spec by making the hole narrow.
     
    BikeBuilder43 likes this.
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