Uneven Acceleration

Discussion in '2-Stroke Engines' started by slimshady, Nov 8, 2010.

  1. slimshady

    slimshady New Member

    So I'm new to the motored-bike world, and with my first build finally finished, I was disappointed to find that my bike does not accelerate smoothly. When i pull back on the throttle, the engine doesn't seem to accelerate, and suddenly the speed increases. Then, when I try to decelerate, the engine doesn't slow at all, it just maintains speed :confused:

    Another question I had was how do I set up the motor so that when i start it up, I don't have to use the choke? Is the choke necessary for startups? Mine doesn't seem to want to start without it.

    Thanks in advance :evilgrin:
     

  2. motorpsycho

    motorpsycho Active Member

    you only need the choke when the air is cold. 9 times out of 10, i can start mine without using the choke.
    there is no way to "set the engine up" to start with or without the choke. some engines need to be choked to start, some don't.

    your acceleration problem could be an air leak at the intake tube where the carb. goes on.
     
  3. slimshady

    slimshady New Member

    I guess I have an issue then because my engine rarely starts and when it does, it grunts at random intervals giving a little power and then dies out. Any suggestions? Also, I am using synthetic oil but its not for 2 strokes. I don't know if that could be an issue...

    I checked the intake tube and it seems fine. Another question I had was how much play should I have on my throttle? I think I have too little. How do I fix this if there is too little play?

    Thanks
     
  4. motorpsycho

    motorpsycho Active Member

    if you are using synthetic motor oil and not 2 stroke oil, that would probably be your problem.
    you must use oil made for 2 strokes, either regular or synthetic....but it MUST be 2 cycle oil.

    you should have a little slack in the throttle cable so that when you turn the handlebars left to right, the cable isn't being pulled. this could possibly cause your bike to accelerate while turning, and that's a bad thing.

    The throttle cable should have an adjuster on it up close to the throttle handle assembly. it looks like a 90 degree peice of steel tubing with threads, a threaded sleeve and a nut on it. the end screws into the throttle assembly and it has the cable going into it with a threaded sleeve and a locking nut.
    loosen the nut and screw the sleeve in (tighten) to loosen the cable, screw the sleeve out (loosen) to tighten the cable. what you will be doing is making the tube longer or shorter depending on which way you turn it, and by doing that it will take up or add slack to the cable.
    once you have the sleeve where you want it, tighten the nut against the sleeve. the nut will lock against the sleeve so it doesn't move.

    [​IMG]
     
  5. slimshady

    slimshady New Member

    Thanks. So, until I can buy 2 stroke oil, is it ok to leave that oil-gas mix in my bike? I wont run it but can it sit there or will it screw something up?
    :evilgrin:
     
  6. motorpsycho

    motorpsycho Active Member

    well, as long as you don't run it, it won't hurt anything.
    But I would drain that gas/motor oil mix out of there, and start over using a good quality 2 stroke oil.
    you should probably srat out with a 20:1 gas/oil mix, and then adjujst it from there.
    I run mine @ 32:1, but my engine is broken in already...not sure if yours is broken in or not.
     
  7. slimshady

    slimshady New Member

    I am also having trouble idling. When I pull in the clutch to disengage the engine, instead of reving slowly, the engine revs extremely fast and starts shaking the whole bike. Is there any way to slow this? Ive tried the screw.
     
  8. jaguar

    jaguar Well-Known Member

    Sounds like you either have an intake air leak or you need richer jetting.
     
  9. A_FITZ

    A_FITZ Member

    Is the bike running and taking you where you need to go?

    Engine Revving Fast, you mean upon start up from a roll, it jerks? Mine does that too from a rolling start.. they just have high acceleration. Slowwing it? ask these guys lol..

    And if your moving fast, the bike will vibrate going over 25mph. It sucks. I know.

    Also my bike wont start or run until I have the Choke lever adjusted just right where the bike wants it.., hair adjustments will help.

    Other then that im just an expert compared to these guys.., I just know that setting up the choke right matters allot, especially in the cold.
     
  10. slimshady

    slimshady New Member

    Now my acceleration issue is gone but the chain keeps coming off. Anyone else have this problem? My hypothesis is that the chain is way too tight on there. Could that be the reason? Thanks :evilgrin:
     
  11. GearNut

    GearNut Active Member

    Improper sprocket alignment is the biggest cause of chains falling off. The next cause is a chain that is adjusted too loose. There should be 1/2 inch of free play on the slack side of the chain.
    The factory chains are also known to be trash right out of the box.
    It should also be noted that some of the sprockets, both engine and rear wheel, come from the factory with burrs on the teeth that need to be smoothed out. Also on some of the the engine sprockets the valleys between the teeth are machined too deep and the tips of the teeth need to be very carefully filed just a little bit shorter to fix this problem.
    This must be carefully looked at though. Do not assume any of the problems are actually there and merrily file away at the sprockets. Look closely at how the chain wraps around the teeth and see if it is getting hung up before modifying the sprockets.
     
  12. slimshady

    slimshady New Member


    Where do I buy better quality chains?
     
  13. GearNut

    GearNut Active Member

    I got mine at a local independent motorcycle shop. A Tsubaki 415 standard non o-ring for $20.00.
    Some folks here get theirs from the vendors that advertise on this site.
    Pirate cycles comes to mind. They sell a decent quality chain at a fair price. Other folks get chains from Tractor Supply.
     
  14. handyandy91

    handyandy91 New Member

    Yep, my chain that came with my 66 cc starfire would not fit my 40 tooth sprocet.
    The first 10 or so links went around fine then boink, no more fit^@#$!!!
    Put on a Tractor Suply #41 chain, Fit awsome!!!!! :)
     
  15. slimshady

    slimshady New Member

    thanks guys. umm i have another question, my back wheel is wobbly when it rotates. by this i mean that when i accelerate, it wobbles side to side. i didnt even notice this until my friend told me how screwed up it looks when he saw me ride it. so im curious... how do i fix this? is the wheel screwed up? or can i do something to fix it? thanks.
    :evilgrin:
     
  16. GearNut

    GearNut Active Member

    You will have to hold the rear wheel off the ground and spin it. Look to see if the rim needs truing up, the tire is not seated properly on the rim, or the wheel bearings are set too loose.
    Truing a rim on a wheel assembly is not hard if you have the patience to do it.
    Re-fitting a tire on a rim is easy.
    Properly setting the wheel bearing pre-load is also easy, it just usually takes a few tries if you are not familiar with doing it.
     
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