Engine Trouble 66/80cc idle adjustment?

Discussion in '2-Stroke Engines' started by Joe, Jan 6, 2012.

  1. Joe

    Joe New Member

    Searched and I haven't found any info on this.

    First off, this a new build and my first build.

    So the problem is, I can't get my engine to idle. It runs, but I have to keep it at part throttle to keep it running. I've messed with the little screw on the side but I get nothing. Is that idle speed or idle mixture adjustment? There's only the one screw. All parts are stock.

    Thanks,
    Joe
     

  2. wan37

    wan37 Member

    If there's one screw it's Idle screw.Do you now what carb it is?
     
  3. toojung2die

    toojung2die Member

    Every new build I've seen needs an o-ring to seal the carb to the intake manifold. Tuning the carb or getting the engine to run right if there's an intake air leak will be difficult or impossible. You can buy o-rings at any hardware or home improvement store. Bring the intake manifold or carb with you to get one that fits snug. Lacking an o-ring you can use silicone gasket sealer but you have to wait for the silicone to set. Make sure the manifold to engine gasket isn't leaking too. A little silicone gasket sealer on this spot helps ensure a good seal.

    That screw adjusts idle speed only. There is no mixture adjustment screw. Air/fuel ratio is set by the main jet size and position of the clip on the throttle slide needle. Changing the position of the throttle slide needle is only required for partial throttle mixture adjustment and it usually will idle without changing it's position in the beginning.
     
    Last edited: Jan 7, 2012
  4. motorpsycho

    motorpsycho Active Member

    I'm placing my bet on the carb slide being 180 degrees off.
    if you take out the slide in the carb and look at it, you will see that it has 2 slots cut into the sides of it (a long slot, and a short slot).
    the long slot goes to the right side of the carb and gets lined up with a small pin that's cast into the inside of the carb body.
    the short slot goes to the left side of the carb and will line up with the idle screw.
    if the long slot is on the left side (where the idle screw is), the idle screw will have nothing to contact on the slide, so it can't raise or lower the slide to increase/decrease the idle.
    I don't know how many times i have heard this problem, and how many times i have seen the carb slide installed wrong. it can go into the carb 2 ways, but only one way is right.
     
  5. wan37

    wan37 Member

    I will place my bet on motor ,because I have done it and it would rev very high if a air leak....lol
     
  6. motorpsycho

    motorpsycho Active Member

    oh, one other thing...
    are you sure that the choke isn't stuck closed?
     
  7. Al.Fisherman

    Al.Fisherman Active Member

    [​IMG] [​IMG] [​IMG]

    http://www.youtube.com/watch?v=lbtDMFUiD0k
    At the 10 second mark the choke is open (running position)
    At the 19 second mark the choke is closed, on some bikes the choke needs to be anywhere between open and closed to start. On my engines, normal start position will be open.
     
    Last edited: Jan 7, 2012
  8. Joe

    Joe New Member

    I noticed the two slots when I was putting the cable into the slide. I took it apart thinking that was the problem, but I had it right. It was then that I noticed the notched and angled portion at the very bottom and how it lined up with the idle speed screw. So the good news is that it does idle now! However, is an erratic idle normal? I had some cork gasket material and made a gasket to go between the intake tube and carb. So I doubt there's a leak there. IDK... I'm thinking a little bit longer intake manifold might help.

    Like I said, this is my first build. I'm learning that these are not ready to go out of the box... after assembly of course. That chain tensioner is WORTHLESS!! The welder is going to get good use tomorrow!

    Thanks for the help!
     
  9. HeadSmess

    HeadSmess Well-Known Member

    define "erratic" please :jester:
     
  10. motorpsycho

    motorpsycho Active Member

    a cork gasket between the intake tube and the carb? the thing to cure an air leak at the carb /intake tube connection is to install an o-ring in the end of the carb and then slide the carb onto the intake tube so that the o-ring seals between the tube and the carb.
    please explain how you did this with the cork gasket, because if you did what i think you did, part of the intake tube may be blocked by the gasket.
    in "erratic" do you mean that the idle speeds up and slows down on it's own?
    normally if you have an air leak, the engine will idle REAL high and you will have zero throttle response when you twist the throttle.
     
  11. Al.Fisherman

    Al.Fisherman Active Member

    Food for thought....If the cut out angle on the slide doesn't line up with the idle screw, the pin in the carburetor can't be lining up correctly with the cut away that the cable fits into. As the two are 180 degrees apart.
     
  12. Joe

    Joe New Member

    In the kit I found a small red, round gasket. The instructions were lame and did not mention it or even where to use it, so I used that between the carb and intake tube. THAT was a mistake! When I took the carb off to address the idle issue, the little red gasket was missing. It had been sucked into the intake. Fortunately, it didn't make it into the engine. I took the intake tube off and got it out. I used that as a rough template to make the new gasket from the gasket material I had. It fits in the carb very snug, so I don't think it will get sucked in. But I know somewhere I have an assortment box of rubber O-rings so I'll swap one in.

    Yes, by erratic I mean that the engine speed goes up and down on it's own. Not by huge a amount though. Couple hundred RPM up and down. What is normal idle speed? Right now I have it set pretty high IMO. But if I lower it too much more it will die. I've watched alot of youtube vids and at this point I can't get mine to idle that smoothly.
     
  13. motorpsycho

    motorpsycho Active Member

    wrong....the cable has nothing to do with where the 2 slots in the slide are.
    the cable goes into the long slot but it ends up coming out of the top of the slide. The cables orientation in the slide doesn't make any difference. it will always have to come out of the top center of the slide / carb cap so wheather the cable slot is on the left or the right, will not matter to the cable.
    if the slot for the idle screw is not lined up with the idle screw, the slide will not go all the way down into the carb because the pin will not have a slot to slide into and it will stop the slide from going all the way in.
    yes, you slide the cable into the long slot, but once it's in that slot, it ends up in the center of the slide.
    the slide can and will go into the carb 2 different ways but only one way is correct. the cable will always end up in the center of the slide no matter how the slide is put into the carb.
     
  14. motorpsycho

    motorpsycho Active Member

    ok, first of all, gasoline will destroy a rubber o-ring. BUT, you can try a rubber o-ring temporarily just to see if it solves the problem.
    you need to go to sick bike parts and order some of their o-rings specifically for this. They are made of fuel resistant Viton.
    here's a link for the o-rings.
    http://www.sickbikeparts.com/catalo...ducts_id=51&osCsid=01eg3n4lovo147vqjd0cvknf75
    i suspect that you may have a float adjustment issue which could be causing the erratic idle. if the float level is set too low, your carb could be getting close to running out of gas, which will cause a lean condition, and make the rpms go up. Then the float bowl re-fills which will richen the mixture, causing the rpms to go back down. whenever an engine runs out of gas (float bowl empty, gas tank empty) the engine rpms will increase on their own right before the carb runs out of gas completely. this is making it run lean (too much air, not enough fuel).
    either that or you have a tiny air leak either at the carb-intake tube connection, at the intake tube - engine gasket or at the carb cap. the carb cap shoudl be hand tight only, but they can still leak because the machining . casting isn't the best.
    someone had this problem and they put a small gasket under the carb cap and it cured it. I'm not sure what they made the gasket out of tho. I think they just used a fiber washer....I can't remember.
    go get yourself a can of starting fluid.
    With the engine running LIGHTLY spray the starting fluid around the connection between the carb and intake tube, the intake tube and engine gasket and the carb cap. if the rpms go way up when you spray one of these areas, you've found your air leak. do one area at a time and let the engine run for a few seconds between sprays so you know which area the leak is coming from. if you spray the whole carb at once and you do have a leak, you'll never know where it's coming from.

    second of all, your idle should be smooth and it should never vary in rpm...just like your car. your engine should sit there and idle smooth..mine will idle all day long and never change. what is the correct idle speed? well, that's all personal preferance, there is no "right" idle speed. as long as it's not racing really high, and able to stay running when you let off the throttle with the clutch in. that's all that really matters. you juyst want a nice, smooth "pop-pop-pop-pop" idle
    for example, here's a video of one of my engines sitting at an idle. I do rev it on occasion but i was trying to show the sound of my custom exhaust.
    http://www.youtube.com/watch?v=Ry-Sjb_HQao
     
    Last edited: Jan 8, 2012
  15. Joe

    Joe New Member

    Well ****! The little gasket I made to go between the carb and intake tube is missing. It's not stuck in the intake tube like before. Hopefully it's made it's way into the muffler. Runs fine though. I'll still get a proper o-ring. Haven't been working on the engine much though... been focusing on my chain tensioner. Very VERY happy with it! The chain doesn't bind up at all anymore!

    IMG_0381.jpg
     
  16. Al.Fisherman

    Al.Fisherman Active Member

    So what's your point....look at the pictures in the above post #7.
     
  17. toojung2die

    toojung2die Member

    That's one of the best spring loaded chain tensioner design I've seen yet. Well done. Where did you get the bushing for where the arm pivots? The idler sprocket is bigger than the derailleur idler sprockets often used. What is that idler from?
     
  18. Joe

    Joe New Member

    Thanks!

    The bushing is a shouldered brass bushing I bought at Lowes. 1/2" o.d., 3/8" i.d., 1" length. The idler sprocket I bought from Tractor Supply Company. Came complete with a sealed, pressed in roller bearing. I went through several springs though. The one that worked best had a .105" diameter wire. Tried .062"... WAY to soft. .120" was way WAY too tight. Bought the correct spring from my local Ace Hardware. But TSC had a good selection. Too far of drive from my house for just a spring.

    So far I'm using graphite lube from an aerosol can on the pivot bushing, but I'll clean that off and use regular wheel bearing grease. I'm thinking the graphite will wash off from splashing through a few puddles.

    So far I'm very happy with it. Need to put more miles on it to really test it. As you can see the pivot point is only in single sheer right now. We'll see if it loosens up and needs to be placed in double sheer.
     
    Last edited: Jan 9, 2012
  19. motorpsycho

    motorpsycho Active Member

    nothing, i totally misunderstood what you said.
    I thought you were trying to say that the cable would not line up with the carb cap, if the slide was in 180 degrees off.
     
  20. motorpsycho

    motorpsycho Active Member

    that is one of the best tensioners i've seen too!
    quick, patent the idea, make some and start selling them.
    People will buy them.
     
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