50 to 44 tooth swap

Discussion in 'Motorized Bicycle General Discussion' started by Derks420, Jul 28, 2010.

  1. Derks420

    Derks420 New Member

    Joined:
    May 30, 2010
    Messages:
    114
    Likes Received:
    1
    Hey guys, i recently changed my rear sprocket of my 49cc 2 stroke after breaking the engine in, from a 50 to a 44 tooth. The original setup i got a top speed of about 32/33mph. I swaped the 44 expecting to gain a little speed, but it tops out right aobut the same, around 32mph or so. Whats goin on? First of all, i only weigh 125 pounds, so i know there is no weight issue. i have heard people saying they hit 40mph. Do i need a smaller sprocket? maybe a 41 tooth? i also headrt that the 41 tooth is perfect for 49cc engines, reduces vibes and increases to top max speed. Is that true? any help would be appreciated. Also I am using a 24 inch tire if that makes a difference..... Thanks....De.shft.rks
     
  2. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

    Joined:
    Mar 20, 2008
    Messages:
    6,215
    Likes Received:
    25
    Now you need to tune the engine! ;)
     
  3. andrewflores17

    andrewflores17 New Member

    Joined:
    Jul 12, 2010
    Messages:
    479
    Likes Received:
    0
    when i had my 2 stroke i went from the 44 to the 36 tooth i was able to hit 45 mph doing that and takeing the baffle outa the exhaust word of advice though starting becomes harder u have to pedal up to a pretty good speed and u wont climb a hill or take off as fast but u will go faster from experince
    and with my 4 stroke went from the 44 tooth to the 50 couldnt climb a hill for the life of me without going up so its at the perfect middle ground lotsa speed decent ability to go up a hill

    well hope this helps

    ps dax should sell um
     
  4. BarelyAWake

    BarelyAWake New Member

    Joined:
    Jul 21, 2009
    Messages:
    7,209
    Likes Received:
    5
    ...and this is exactly why we're so hard on unsubstantiated speed claims - while what you've gotten for speed is pretty much normal out of a stock kit & it's not impossible to hit 40mph - just doing a sprocket swap is in no way gonna do it, it takes quite a bit of tinkerin' and a few aftermarket performance parts for the average HT 2 smoker, a heck of a lot of tinkerin' for the 49cc. Yet when peeps jump in here and blithely throw around w/e speeds they think sound impressive or even just "guessing" what speeds they think they're going - it gives folks false expatations and disapointment, they think their engine is a dud or something.

    Weight and sprockets mostly effect acceleration & cruise RPM, your "0-30" if you will, it's overcoming wind resistance and parasitic drag that's the problem when discussing top speeds - and simply put, that takes more power (and/or drag reduction)... there's no way around it.

    Your speeds sound just about right Derks (actually pretty good for a 49cc), check out our High Performance Bicycle Engine Tips section for some tips and tricks to get the most outa yer motor... yankin' baffles out mostly just annoys the neighbors, unless you've the catalytic converter it's really not unduly restrictive - it's just not a proper exhaust system for a two stroke, you need a tuned expansion chamber to get a real power increase. People commonly mistake noise for power is all ;)
     
    #4 BarelyAWake, Jul 28, 2010
    Last edited: Jul 28, 2010
  5. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

    Joined:
    Jan 8, 2008
    Messages:
    11,529
    Likes Received:
    3
    You bike won't go any faster with the smaller sprocket because you have gear it to where it can't get to it's power peak....if you gear even higher, you will gain nothing.

    If you are getting 33mph out of a 50cc kit, you are doing quite well.
     
  6. severedcorps

    severedcorps New Member

    Joined:
    Jul 13, 2010
    Messages:
    54
    Likes Received:
    0
    i only hit 22 mph.. with the 44T and a 49cc chinese 2 stroke... WTF

    i don't understand how everyone else posts such high speeds, I can't even get to 25 mph
     
  7. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

    Joined:
    Jan 8, 2008
    Messages:
    11,529
    Likes Received:
    3
    Because the are full of you-know-what, or they have an inaccurate way of reading their speed. Having said that, I will say this- some engines will rev, and some won't.

    I am not calling anybody a liar, so don't get your panties in a bunch. The first bike I built, I SWEAR would go 45 mph as clocked by two cars, most called me a liar, and the rest of the bikes I built wouldn't even come close to that speed. I wish I had that engine now that I have GPS.
     
  8. Derks420

    Derks420 New Member

    Joined:
    May 30, 2010
    Messages:
    114
    Likes Received:
    1
    Hey guys, thanks for the info..... If you say that im running as quick as i can I believe ya.
    And with reguards to tbhe top speed.... like i said, i have seen others post 40 mph, and when i said i top out around 33 or so, i wast guessing. I have a correctly calibrated speedo, and have had my brother tail me in his truck and confirmed it. There is no reason to lie. But thanks for all the help guys! Ill just keep fine tunin!!
     
  9. BarelyAWake

    BarelyAWake New Member

    Joined:
    Jul 21, 2009
    Messages:
    7,209
    Likes Received:
    5
    This too is not particularly uncommon, without checkin' out the bike it's just wild guesswork but I'd do the basic check for air leaks (if you've not already) and some simple manifold port-matching: http://motorbicycling.com/f13/basic-porting-time-fer-teh-lolz-16646-2.html#post164391 to start with.

    While some engines are just "duds" many of them (read most) just need a good going over ta get the sloppy outa 'em :)


    Derks, lol - we don't think yer stretching the truth any as yer speed sounds about right/slightly bettrn' average - & 40+ isn't impossible either, it's just being the internet... well... ya know how it goes laff
     
  10. Derks420

    Derks420 New Member

    Joined:
    May 30, 2010
    Messages:
    114
    Likes Received:
    1
    "Derks, lol - we don't think yer stretching the truth any as yer speed sounds about right/slightly bettrn' average - & 40+ isn't impossible either, it's just being the internet... well... ya know how it goes"

    Yea, Deffinitly some fibbers.....
     

Share This Page