Getting the bike ready for the spring...

Discussion in '2-Stroke Engines' started by tylerscool45, Feb 16, 2010.

  1. tylerscool45

    tylerscool45 New Member

    I wanted to start getting my motorized bike up and running soon.
    Last fall i was riding it my clutch broke and engine sproket tooth broke.

    Got a new sprocket recently and replaced it.

    It has a few problems though...

    The engines heat sink(sorry i dont know the exact name) must have gotten
    real hot over the time i had riden it and the fans(sorry) have seemed bent slightly. My friend says it wont start, but has anyone else had these problems with grubee engines?

    Next, my clutch is extremely hard to pull and its been like this since i got it, is this normal or is there something i can do about it.

    Finally, right before summer last year i broke it and since i fixed it after my throttle seems to accelerate accelerate and then makes a weird noise and decelerates even though my throttle is fully open.

    If anyone knows how to fix all or any of these problems help would be greatly appreciated.

  2. AussieSteve

    AussieSteve Active Member

    tylerscool45, your post about heatsinks and fans makes very little sense.
    I would suggest that you jump onto Wiki or somewhere and learn a tiny bit about 2-stroke engines, in particular the names of a few of the main parts and especially the names of the parts that you're having trouble with.

    These clutches are all hard to pull in, out of the box.
    First, oil the clutch cable, if you haven't already.
    Next, pull off the countershaft sprocket cover, remove the pin from the centre of the shaft, put a dab of grease in the hole and replace the pin.
    Put a dab of grease on the end of the pin.
    Finally, ensure that the small pivoting shaft with a semi-circular cam on the end is well greased. If you turn it and pull, you'll find that it comes out easily for greasing.

    If your clutch is still too stiff, there are two more ways to improve things.
    The first is a bit of grinding and smoothing:- Another useful HT clutch mod

    The other way to make the clutch easier to use is to buy a clutch roller setup from Al.Fisherman. The relevant thread is here:- For Sale..Clutch roller bracket for HT
    If you do both mods, even a baby could pull your clutch in.

    What broke?
    What type of weird noise and where does it come from? ie exhaust, clutch, etc.

    You really do need to be much clearer if you expect anyone to help you.

    ... Steve
    Last edited: Feb 17, 2010
  3. motorpsycho

    motorpsycho Active Member

    man, i don't mean to be rude..but did i just read about heat sinks and fans?
    are we talking about a computer, or a 2 stroke engine?

    That's the same as saying "the doohicky won't line up with the thingamabob, and the johnson shaft is bent".
  4. tylerscool45

    tylerscool45 New Member

    Im sorry, i dont know too much about motors but i know alot about computers so i just called it that :D.

    And as for the noise its coming from the engine... it accelerates then decelerates and makes a weird noise and the rpms slow and so does the bike.
    What broke was my clutch before. My friend who knows about motors says its something with the carb but i tried to fix it and it won't fix, so i don't think its the carb.
  5. AussieSteve

    AussieSteve Active Member

    I surrender. Get your friend who knows about motors to have a look at it.
    I'm sick of trying to help people who won't help themselves. I'm outta here.

    ... Steve
    Last edited: Feb 18, 2010
  6. tylerscool45

    tylerscool45 New Member

    ok whatever thanks for the help with the clutch at least
  7. AussieSteve

    AussieSteve Active Member

    One more try:-
    As I said in my last attempt, please do a little reading, learn a few names, and try to describe things accurately. I suspect that the heatsink is the cylinder and/or head and that the fans are fins, but I'm only guessing.
    (A deal - I'll be a little more civil if you do a little bit of reading.)

    Once again, what type of weird noise and where exactly does it come from? (Not simply 'the engine') Even LHS front, RHS rear etc will help, along with the type of noise - grinding, backfiring, squealing, clunking etc.

    If you don't know just what's wrong with the carb, how did you try to fix it and why won't it fix?

    ... Steve
  8. tylerscool45

    tylerscool45 New Member

    Ok ive taken some pictures to help explain my problem.

    First i beleive your correct that they are fins i should have known that haha, but anyway my worry about them is they are bent and my friend said to replace the motor and not even bother putting it back together, because he beleives it wont even start or it will break within the first few minutes, even though ive only used it on year.

    My friend told me that may be the problem... So him and i tried to fix it with no luck that's what i was talking about. The picture below with the screw is what we thought was the problem but obviously wasn't.

    Now for the noise ill have to get back to you on that one, probably tommorow because i have to put it back together to make sure exactly what im hearing. But ill try to explain exactly what i mean because this didn't happen when i first got it, and its about 5-10 mphs slower now...

    Before it would accelerate and accelerate and max out rpms.
    Now it accelerates accelerates then almost sounds like the motor is going to
    shut off and lowers rpms, but ill give you a sound clip when its ready to show you exactly what i mean by the sound. The way for it to go the fastest is to find the best spot like when the throttle is like 75% open, after 75% it decelerates.

    Attached Files:

  9. AussieSteve

    AussieSteve Active Member

    I thought that the pics might show the bent fins that your friend says will stop the engine from working. Generally speaking, bent fins won't do any harm. A pic of that will help, but you probably have nothing to worry about on that score.

    The screw on the LHS of the carb body is the idle speed screw. When your engine is running, turn it in to increase idle speed or out to decrease it. It doesn't affect the fuel/air mixture, only idle speed.

    Now, to the real problem. What you're describing sounds like your fuel/air mixture is possibly too rich. The weird sound might be 4-stroking, a situation that occurs when there is too much fuel and not enough air in the combustion chamber, causing the engine to only fire on every second revolution. Does that ring any bells?
    The slide needle controls the mixture up to about 75% throttle, then above that the main jet takes over, from 75% to wide open throttle, (WOT).
    My bike did that out of the box and couldn't rev out above 33kph. I finished up working my way down from an 0.79mm jet to an 0.72mm, before I could get it to run well. Then, top speed went up to 51kph - much more respectable. (This was all before I fitted my shift kit - speeds are much higher now.)

    So, you could try a smaller main jet and see how it goes. I've built up a small collection of jets for tuning.
    I get mine from OzMiniMoto in Australia, but you might be able to get them from somewhere closer. Dellorto 5mm jets are suitable. DellortoDirect sell them, too, although I had a bad experience and won't be dealing with them again.

    Mind you, it might be something entirely different. It's interesting that it only just started doing it.
    See what, if anything, others have to say.
    A sample of that sound would help.

    Check this out:- Four Stroking (Thanks again to Al.Fisherman for originally pointing this clip out.)

    Is that the sound?

    ... Steve
    Last edited: Feb 18, 2010
  10. tylerscool45

    tylerscool45 New Member

    Thats it man :tt1: Sounds exactly like that video when hes "four stroking"

    Thats for sure what it does, i could buy a new jet, but i don't know exactly which one ill need theres so many to choose.

    I don't know if this will help at all, but before i broke the clutch and before it started acting up, that same day one of my friends used quad gas as i was out, i told him not to use it but it was already in the tank, he said it doesn't make a difference so i drove it home, and rode it after that with the quad gas in there for a while,then after a week or so after my clutch broke. You don't think the quad gas could have screwed it up do you?
    Last edited: Feb 18, 2010
  11. AussieSteve

    AussieSteve Active Member

    Good stuff - looks like we're getting there. That video is good, isn't it? A million words on paper wouldn't describe it as well.

    Deciding which size to get isn't easy, that's why I bought a range of jets.
    Some carbs come with an 0.7mm main jet standard, while others have an 0.79mm and occasionally 0.6mm.
    When I started tuning I had to assume that my stock jet was 0.79, so I started by buying the 0.76. When that improved things, I bought a range of jets going down in size from 0.76.
    To determine the size of your original jet, you could buy the 0.76 then visually compare it to your stock jet. If the 0.76 looks smaller, you're on the right track.
    Is your's a 48cc or 66cc?
    Since it is so rich, you probably have an 0.79. If so, you could probably buy an 0.76 and 0.74 then try each. If you still have the problem at 0.74, then you might have to go smaller. If you can spare the $, buy an 0.72 or 0.73 as well.
    As I mentioned, my 66cc likes an 0.72mm main jet. That was also the size recommended by Tony Ciccio at Rock Solid Engines.

    A quick read of this might help, too:-
    NT Carb Tuning Basics

    Among other things, it shows the location of the main jet, screwed into the end of the slide-needle jet.
    N.B. In the pics, I mis-labelled the slide-needle jet and mistakenly called it a float needle jet.

    ... Steve
    Last edited: Feb 18, 2010
  12. tylerscool45

    tylerscool45 New Member

    Ok great man, Im gunna buy some jets and test them and get back to you. Im also gunna buy that Clutch roller bracket you showed me.

    Mines a Grubee Starfire 48cc

    Im also gunna pick up a Dual Pull Brake lever.

    Thanks a lot for the help!!
  13. AussieSteve

    AussieSteve Active Member

    No worries - glad to help.
    Let us know how you go.

    ... Steve