80cc acceleration issues

Discussion in '2-Stroke Engines' started by Travis, Mar 23, 2010.

  1. Travis

    Travis New Member

    ok i have had this engine for about 3 tanks and speed wise ive topped it at 30 mph(i weigh 250lbs) on average i cant pass 25mph and when i hit 25 i feel a little pull and then it picks up then pulls over and over as though it had a governor (obviously not the cas as i can occasionally hit 30) how do i fix that? and how can i make it go faster like say 35-40? its all stock except the spark plug thats an ngkb6 i noticed it idles higher and louder with that is that good or bad?

  2. professor

    professor Active Member

    I'm sure the HT owners will chime in for you, but my 2cents is the weather affects your jetting giving the impression of it being governed at times. The guys say these are set-up rich to begin with.
    And 30 is about max for a stock motor.
    Any thing that makes it idle higher means it is making it more efficient at that rpm .
  3. Travis

    Travis New Member

    whats up with these boost kits? will it increase my top speed????
  4. Crobo

    Crobo New Member

    what do you mean by boost kids? boost bottles?
  5. motorpsycho

    motorpsycho Active Member

    tuning the carb, putting on a high flow air filter and putting on an expansion chamber will get you more power...quite a bit more power.
    these engines do not breathe worth a darn when they are stock. the stock exhaust is VERY restrictive and the stock air filter is a peice of ****.
    what you are experiencing is a surge, which is usually cased by the carb being too rich.
    What color is your spark plug?
    you want the electrode to be a nice tan color.
    if it's black, it's too rich, if it a light silvery color, it's too lean.

    a boost bottle will give you a little more power in the mid-range rpms, but really, all it will do is make the engine rev up a little faster. a boost bottle is connected to a fitting that you plumb into the intake manifold. a boost bottle is just an empty can, there is nothing inside a boost bottle when you get it. these engines spit back a little excess unburned fuel vapor on the start of the exhaust stroke. the exhaust and intake ports are open together for a slight amount of time and the exhaust causes the fuel vapor to be spit back into the intake manifold. that vapor is blown into the boost bottle and stored until the next intake stroke. on the intake stroke, the extra fuel vapor that is in the boost bottle gets sucked back into the engine.
    it's a very simple but effective process and is kind of the same as supercharging. it will not give you dramatic results....you will notice a difference, but not like you added another 50 c.c.s to the engine. it's a simple way of cramming more fuel vapor into the engine.
    i put one on my bike and i didn't notice any difference at all. but, my engine does not have an intake manifold so i plumbed my boost bottle into the rear of the air filter. it really didn't work hooked up that way because it was too far for the fuel vapor to travel to actually make it into the boost bottle.
    Last edited: Mar 23, 2010
  6. Travis

    Travis New Member

    www.boostinductionsystems.com/bis-racing_home_042.htm copy and paste that it has nitrous cans and a fire switch thats what i was referring to sorry for the wrong term

    and my spark plug is blackened....how do i fix that?
    also my rear tire warps all the time i have two and i end up needing two have both trued (spokes tightened and wheel aligned)like every two weeks) is there a good rim or a way to fix this also the mounting screws on the backside of the engine(that mount it to frame) seem to have rattled out in my travels where can i buy replacements?
    Last edited: Mar 23, 2010
  7. motorpsycho

    motorpsycho Active Member

    yeah you have a lot going on there.
    first off, to fix the black plug.
    Unscrew the top of the carb. and pull out the slide and the needle.
    You will have to remove the throttle cable either all the way or partially, and pull the needle out of the center of the slide from the top.
    look at the top of the needle, there will be notches and a "c" clip.
    Note which slot the c-clip is in when you pull the needle out.
    move the c-clip up to lean the air fuel mixture, and move the c-clip down to richen the mixture. use a pair of needle nose pliers to do this, and be careful...don't loose the c-clip. you will have to experiement by moving the c-clip one notch at a time and riding it after each time you move it. i would guess that your c-clip is probably in the middle notch, if it is i would raise the c-clip one notch and ride it to see if it's any better.
    by raising the c-clip, you are lowering the jet needle further into the needle jet so less fuel is getting into the engine (and allowing more fuel into the engine if you lower the c-clip, which raises the needle.) remember , put the slide back in the carb so the notch in it lines up with the peg inside the carb body, tighten the cap and take it for a ride. if it's a little better, go one more notch and try it again. this is only a fine tuning tip. if it is running REALLY rich and this will not cure it, you may have to take the carb apart and go to a smaller main jet. I have never done this myself, but from what i understand it isn't too hard to do.
    most guys measure the hole in the main jet with a drill bit, fill the hole with solder, and re-drill the hole smaller.
    I have never done this either, and i'm not sure how easy it is to find smaller main jets for these carbs. and that's why i hear about some guys soldering and re-drilling theirs.
    Usually, moving the c-clip will correct the problem, i think replacing or re-drilling the main jet is in extreme cases.

    not sure why your back rim is warping, but it is possible that your sprocket has too much wobble in it. all of these sprockets will have some wobble in it and there really isn't much you can do about it. (other than buying aftermarket sprocket mounting parts)
    the way to fix it is to take the rim (preferably one that you get trued) and put the sprocket on so the nuts & bolts are loose.
    snung each bolt a little at a time and once the nuts & bolts start to get tight spin the rim and watch the sprocket. you can put the rim in an old pair of bike forks or something that will allow you to spin the rim without holding onto it, and with it being off the bike. you can even tape a sharpie marker close to the sprocket so that it will touch the highest part of the sprocket as it goes by and mark the area that needs to be tightened.
    watch the sprocket for wobble, and tighern the bolts where the sprocket is the worst as far as wobble goes. Make sure ALL of the nuts & bolts get tightened as you do this.
    sometimes you can work the majority of a wobble out of the sprocket by doing it this way....and it takes time to do it. (ja have never actually done it so maybe someone else can correct me if i am wrong about any of this)
    Another tip, replace those stock nuts, bolts and lock washers that hold the sprocket on with some better quality ones from the hardware store. just take a nut and a bolt with you and match them up with some at the store.
    get yourself a bottle of blue loc-tite and put it on every bolt before you put the nuts & bolts together...you'll be glad you did.
    do the same thing with the engine mount screws (studs) at the rear of the engine. i imagine that one of the sprocket bolts may be the same size so try screwing one of them in and see if it fits. if it does, while you are at the hardware store, find some of the same bolts but get them longer. cut the heads off, and you will have studs. you may have to dress the ends where you cut the heads off with a file, but do it gently...then try to put a nut on it and the threads should be ok. again, apply blue loc-tite and they will not rattle loose anymore.
    Last edited: Mar 23, 2010