NRG 140cc twin engine in progress.

Discussion in 'Scooter Projects' started by MARSH, Sep 15, 2013.

  1. scubabiker

    scubabiker NITROJUNKIE

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  2. mrhappy

    mrhappy Member

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    Just finished a 172 twin it's savage racing it this weekend
     

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  3. scubabiker

    scubabiker NITROJUNKIE

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    nice! lot of hours work? did you sleeve a peice between the cranks and then weld them? i love stuff like this! is it road legal too?
     
  4. scubabiker

    scubabiker NITROJUNKIE

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    also good luck with racing this weekend! what class you running?
     
  5. mrhappy

    mrhappy Member

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    Pressed together then welded easy to do now got it figured good
     
  6. scubabiker

    scubabiker NITROJUNKIE

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    do you have a crank key type thing to keep it in place?
     
  7. mrhappy

    mrhappy Member

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    It's welded and pressed in to crank web
    Pic of new crank bearings we run now
     

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  8. MARSH

    MARSH Whooooo!

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    Are you running 2 ignition coils on the stator plate?
     
  9. MARSH

    MARSH Whooooo!

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    I got the twin back from PSN scooters today, they've had it for a few weeks to give it a shake down (damn good thrashing). Anyway Andy set the carbs up, transmission etc and it's still in one piece (crank joint etc) so can't be bad! Running 20.8 hp but on std carbs so pretty pleased. I'll need to fit a new drive belt /clutch as it tops out just over 60mph, getting there slowly. :)
     
    Last edited: May 11, 2016
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  10. MARSH

    MARSH Whooooo!

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    I took the twin out for a little spin, it's "light switch" power, may need to up the roller weight to make it easier to ride on the road!
     
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  11. Merlin

    Merlin Old School Biker

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    I like binary power, it's a bit like the old Yamaha 2-strokes from the '70s, nothing until about 9000RPM, then BAM!
     
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  12. BunnyMum

    BunnyMum Active Member

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  13. seancullen

    seancullen Member

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    With regards to running a 2-1 expansion chamber, I dont think it can be possible, I briefly studied expansion chambers as part of my acoustics module this year for presentation idea's. when a 2t engine fires, it sends out a positive wave of pressure, when this wave gets into the chamber it expands, upon reaching the end of the chamber this wave will bounce back in the opposite direction (thus becoming negative pressure), at the same time the motor will be scavenging, which helps this negative pressure get sucked backwards towards the engine, taking with it some unburnt fuel back into the cylinder.

    If we had a single expansion chamber serving each cylinder then i could only imagine that the positive wave of pressure from cylinder 2 will intefere with the returning negative wave from cylinder one when they collide with each other, usually in physics, when identical positive and negative pressure waves collide they will simply cancel each other out and there will be no wave left at all, which could well happen in this case.

    2-1 systems do exist for 2t motors as mentioned in an earlier post, but I dont think they would be expansion chamber exhausts.

    edit: http://advrider.com/index.php?threads/multicylinder-2-stroke-into-one-expansion-chamber.758526/ ive just come accross this thread on my travels, so it does infact work, how it performs though i cannot say.
     
    Last edited: Jan 28, 2017
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  14. Stevep

    Stevep Well-Known Member

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    twin pipes will be better, what about a quad pipe? 1 into 2 each side? should maintain the back pressure i think
     
  15. MARSH

    MARSH Whooooo!

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    I started the twin up a couple of months ago! That's about it.
     
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  16. MARSH

    MARSH Whooooo!

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    This is now for sale !!
     
  17. Sam phantom

    Sam phantom Active Member

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    Any pics of the finished article?
     
  18. MARSH

    MARSH Whooooo!

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    It's on the Bay but I'll see what I can do !
     
  19. Sam phantom

    Sam phantom Active Member

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    Found it! Very interesting... reasonable price too
     
  20. scubabiker

    scubabiker NITROJUNKIE

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    How much did you sell it for marsh?
     

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