honda moped expansion chamber?

Discussion in 'Motorized Bicycle Welding, Fabrication and Paintin' started by socialdistortionkid, Nov 16, 2014.

  1. socialdistortionkid

    socialdistortionkid New Member

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    Hey guys i havent been on the forum for awhile but i was hanging out with my super chill neighbor and he was drunk and basically told me his wife was *****ing, moaning and complaining that he has too many motorcycles and projects in his garage well anyway he has two identical yellow 1978 honda express nc 50 2 stroke mopeds just sitting rusting in his garage, he bought them over 15 years ago at a swap meet and had the second as a parts bike in case the other honda in better shape would break, and he sold me one of them for a whopping $20 lol.... dance1 anyways does anybody have any experience with these? Ive put about $100 of parts into already (new tire, tube, spark plug, fuel line, battery, headlight bulb etc) and it came with no pink slip or bill of sale so i just mailed the dmv a motorized bicycle application for a new title with a money order to the D.M.V.


    Anyways i was looking at the little keihin carburetor it comes stock with and realized that motorized bike parts fit on these too! i was so happy to be the first person to put on a super rat intake, new intake gasket and a NT carb on a honda moped! took me less than 10 minutes to install :) and it runs way better and makes more power and was easy to get it jetted properly...However my question to you guys is what would be the best expansion chamber to put on one of these engines? Right now with the stock pipe Its really restrictive and very slow and struggles going up hills (30mph) top speed.... my options are a kawasaki kx65/kx85 dirt bike expansion chamber, a ktm 50 expansion chamber, a sbp expansion chamber, a pocket bike expansion chamber (cheapest) , or a custom made expansion chamber from a motorcycle shop.... looking for the most power Lemme know what i should do :) i hear these honda express`s are super reliable i just wonder if i put a expansion chamber and a big bore kit will i throw a rod? lol thanks guys
     
    #1 socialdistortionkid, Nov 16, 2014
    Last edited: Nov 16, 2014
  2. joey1320

    joey1320 Member

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    Hi there, nice find on the NC50's!!!

    These are actually regular scooters and not mopeds - called nopeds by the enthusiasts since they don't have pedals ha - and would need a scooter/motorcycle type of license and plate. Make sure you figure that out before going on actual roads cause it can be an expensive ticket.

    As far as those, I have owned 3 and they are extremely reliable once you get rid of the stock carb like you did. The original one is super finicky and it has to be a perfect day, with just the right a amount of moisture, sun, wind velocity blah blah blah for those to work ha.

    Since you removed the original one, I would recommend not throwing it away, you can easily sell it for good money since there are lots of followers who will pay top dollar for original parts.

    All the ones I had I removed the oil pump mixer and just mixed my own fuel. I didn't want to trust a piece I couldn't really see working and it is free to do. Also I pretty much kept them original, so I'm not the best to answer your exhausts question but I would recommend going to mopedarmy.com and asking around to see what others have done.

    Post some pics ;)
     
  3. irishpowerjunkie

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    for exhaust you could try a engine kit exhaust, i know the holes line up and port is same size as pipe, not sure about space, i have the pa50, same engine, but pedals in swingarm.
    also a chainsaw carb can be made work but needs a special filter fitting and choke plate similar to end of kit carb made.
     
  4. curtisfox

    curtisfox Well-Known Member

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    What size chain saw carb did you use?..............Curt
     
  5. Dan

    Dan Staff
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    Good score, Kid!
     
  6. irishpowerjunkie

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    not totally sure to be honest, was off a junked husqvarna chainsaw from late 70's early 80's we puck up intending to fix, never got done. would have been better working if we had a air filter/choke plate like back of cg carbs, bugger to start, hand in to cover inlet and pedal while on it to choke to start, looked ridiculous, but made great difference to revs ill say that though.
     
  7. DEVILSorchard

    DEVILSorchard New Member

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    2 stroke expansion pipes are as much a science as they are an art. Way too many variables with bore and stroke, port sizes, reed valves or piston port to just whip one up and have any expected results with any given engine. If you picked up any 50 cc dirt bike pipe it will probably hit a bit higher in the revs that that engine would like but playing with lead in length can make a big difference to make it work on your engine. If you can find a book called "2 stroke tuners handbook" from around the 70's it's awesome to get your head wrapped around 2 strokeyness.

    If you just want to experiment about any old expansion pipe can work if you cut it into sections and make it slip together so you can play around with the lengths throughout the pipe. Hose clamps work well enough to hold it together for testing then weld it when your satisfied.

    Best of luck these old Hondas where a hoot.
     

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