What more can I do (please read)

Discussion in 'Motorized Bicycle General Discussion' started by Sexypena, Mar 22, 2014.

  1. Sexypena

    Sexypena New Member

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    Okay I've had my motorized bike for about 4 months now and I want speed! I have a 700c thruster fixie bike. So far I've done this to it :
    changed sprocket to 32 tooth

    Bought a "high performance" spark plug Wire and boot

    Put an NGK b6 plug

    Changed out (skull shaped) air filter to new low profile filter I got from bike berry!

    For my fuel I'm running a 32:1 mix. Help what more can I do I'm hitting 37mph top speed with the engine redlining ,I want a cruising speed of 37-40 mph without forcing the engine sorry but I'm not able to get a shift kit don't have that much money
     
  2. Theon

    Theon New Member

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    Shift kit won't get you any faster than a 32t sprocket anyhow.
    By Redline, do you know what revs your doing?
    With a standard motor you may get a slightly better top speed with a slightly larger sprocket, but more revs. your top speed sounds about right for a standard motor, to get even close to 50 MPH, you will probably need either a better motor or port job, hi compression head and expansion chamber. Even then, unless you get everything spot on with a well balanced crank, your looking at about 45 MPH tops.
    50 MPH will be over 9000 RPM.
     
  3. The_Aleman

    The_Aleman New Member

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    Speed costs money, and you're asking a whole lot out of that chinagirl. They simply aren't designed for that much work in the long term.

    IMHO, you're going to need to run a different setup if you want a 37-40MPH cruising speed and keep any semblance of reliability.
     
  4. Henshooter

    Henshooter New Member

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    As Theon said you can only push a standard kit so far and 37 mph is a pretty respectable speed IMHO if you want more speed you first need to think of the fact at 37 a standard bike frame isn't built for anything higher than that therefore reinforcement of the frame and bearings should be considered first , you can get them faster by doing various mods and such like porting and expansion chamber exhaust but I've heard it can considerably reduce the life of the motor and bike , if you really want to push the boundries of speed why not contemplate saving for a road trail motorbike
    If you do end up doing mods and getting more speed just be mindfull of the stability and stresses on the bike and regularly check the frame and running components for stress fractures and most importantly purchase a full face DOT REGULATED HELMET

    Regards and good riding mate

    Henshooter
     
  5. Theon

    Theon New Member

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    I was once told a VW motor could last 500 000 Km if you only rev it to 2000 RPM, for every 1000 RPM above that you halve the life expectancy of the motor.
    So 3000 RPM lucky to get 250k Km
    4000 rpm = 125k Km.
    5000 rpm lucky to get 50 000 Km.
    these motors are just the same, but there cheap!
    I like to take mine up to 9000 RPM, But I don't care how long it lasts, Guaranteed It won't be doing 2000 miles before a tear down.
     
  6. Henshooter

    Henshooter New Member

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    That's some great knowledge to know Theon

    Hope all is well my friend
    Regards Sean
     
  7. wing nut

    wing nut Member

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  8. CTripps

    CTripps Active Member

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    About the only thing I can recommend that won't cost you anything would be to change your oil mix.. 32:1 is okay, but you'll find many here run in the 40:1 area (some higher, depending on the oil they mix with).. At 4 months, it should be broken in enough to go that direction.

    Once you've done that, it becomes a matter of tinkering with/adjusting the needle position in the carb to reduce any missing/misfiring at WOT.

    To get any more out of it, you'd probably need to tear the motor down and do some port work, maybe trim the piston skirt a little for better intake. Lap the head and jug for best seal (and a smidge more compression).

    From there you enter the world of aftermarket parts.. expansion chamber, etc, and needing to spend a bit.

    Now, that being said my beast has a 66cc with a 36T sprocket and a 'speed' carb. The only other mod work done is some cleaning of the ports pre-assembly. Piston skirt is untouched. On a flat run it'll run up to close to 70 kph (44 mph or so). I don't go there very often, as the bike itself starts a 'speed wobble' at around 68-69 kph.

    [​IMG]
     
  9. Theon

    Theon New Member

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    You must have got 'a good one' CT,
    There are so many quality variables in these motors, but pulling them down and going over them, and cleaning up the ports, seems a must if you want that sort of speed.
    Crank balance and port timing holds a lot of them back, but I'm sure they got a few of them right.
     
  10. Thunderhead289

    Thunderhead289 New Member

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    the best thing you can do for these bikes to get more out of a stock engine is to look into the ignition imo. I do a lot of small block ford and chevy related builds and timing advance is everything. not sure what these are set to for initial timing, but they get pretty late after 5000 rpm.

    they really need a progressive spark timing system.

    also higher compression is always a way to gain more power for no money 0$. here is how I did it. it increased the torque by a noticeable amount!

    https://www.youtube.com/watch?v=ZMMbWtStkTY
     
  11. 2door

    2door Moderator
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    Thanks for posting the vid showing how to lap the cylinder head. That is a process that should be done even to a new engine. The only suggestion I could add would be to use a sheet of glass under your sandpaper instead of wood. You'll get a little more precise job.
    Also I like to clean the gasket surface before I begin and 'paint' it with a magic marker or if you have it, machinist dye. That way you'll quickly see where there are any imperfections or high and low spots. They'll show up after just a couple of swipes across the paper.

    The trick is to not sand in an angle. That means keeping the head square to the sandpaper/glass. I do the cylinder the same as the head. You'd be surprised how often you'll find the cylinder gasket surface not much better than the heads.

    Tom
     
  12. mapbike

    mapbike Active Member

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    You will not ever get a single speed china girl build to run over 35mph without it being at a high rev, I have one bike that has seen 45-48+mph and that is running a 36T sprocket wound up as tight as a fiddle string......... it cruises at 40-42mph comfortably.

    The engine has had some port work I did and basically a straight through exhaust with a well tuned NT carb.... 9000+ RPM several times but I tey to keep it toned down a bit so it will last a while longer.

    On a basically stock engine 37mph with a nice cruise speed at 32-34mph is not bad.

    Map
    .wee.
     
  13. mapbike

    mapbike Active Member

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    Ditto........
     
  14. Sexypena

    Sexypena New Member

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    That's true as long as I can keep with traffic I'm fine "you can only push a china girl so far"
     
  15. Sexypena

    Sexypena New Member

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    Any way I can boost my torque /acceleration cause with the 32 tooth sprocket it takes a while to get up to speed I weigh about 165
     
  16. Theon

    Theon New Member

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    Do a compression Test.
    try and get your compression up around 145-150 PSI by shaving the head, That's the cheapest mod for better acceleration.
     
  17. Sexypena

    Sexypena New Member

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    I don't know how to do that or if I have the tools and equipment to do a compression test
     
  18. Theon

    Theon New Member

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    Surely someone does?
    Take it to a mechanic, and ask them to do it then.
    this is the simplest and possibly cheapest way I can offer,
    Bolt on's aren't going to help much, unless your already have the motor working the best it can.
     
  19. Theon

    Theon New Member

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    Get a 36t sprocket.
    32 is to small for a standard motor.
    Infact a 40t would be even better for a standard motor.
    If you don't know how to get your compression right, no point me explaining how to get your port timing right.
     
  20. mapbike

    mapbike Active Member

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    I have run 36T on stock well tuned xhina girls with a good free flowing e haust with great results, 32-34 mph cruise speed all day long and 37-38mph top vibrate your socks ofd speed.....lol!

    If the carb isn't jetted right and the exhaust is rwstrictive you wont ever have good top speed and hill climbing power period..... no matter what sprocket is used.

    All I can vouch for is my own experiences with my bikes and all the changes I've made on them over the years, a well tuned NT carb will give you a good cruise speed if all else is right no need for a big honking carb unless there is a lot of work done on the engine, the RT dellorto sha clones are good for low and mid power but do not get me the top speeds that I've got from the little NT carbs, they just need to be jetted right once you get everything else where you want it for best performance.

    Personally I think the 36T sprocket is the best all around sprocket if your area isn't way to hilly and your weight. Isn't to high, im at 210lbs and I cruise at 42mph nicely on my fastest bike and its running a 36T and it pulls me up all the hills around where I live with ease.

    Map
     

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