Clutch New 48cc Engine, clutch noise

Discussion in 'Transmission / Drivetrain' started by wrinkledoggi, Dec 5, 2009.

  1. wrinkledoggi

    wrinkledoggi New Member

    Hi guys - just ran my Huffy Cranbrook w48cc for the first time(s) yesterday and today, finally got the thing to idle properly after adding an O-ring inside the carb cap . . . worked like a dream! Now, I feel lots of chunking and hear chattering and whine from the clutch . . . . how do I adjust properly? Can someone give a clear step-by-step? Thanks . . . . . Mark

  2. happycheapskate

    happycheapskate Active Member

    o ring good idea, what size?

    I was thinking the same thing. Mine runs great but I wondered if the lopey idle was from the muffler I used or the carb junction leaking. Hard to know without maybe trying a little hose on it to see.

    If its the grubee type, you are supposed to adjust the clutch lever the best you can to relieve the clutch, and tie down the lever/use the locking pin on the lever if you have it. Now open the case on the right side (not the bottom of motor) There is a locking nut, and a star shaped finger nut. Loosen the locking nut, then adjust with the finger nut, and lock down. The clutch should let you pedal without dragging on the clutch, as long as the lever is pressed down, then let you "pop" the clutch to start the engine. Let it out slowly, don't dump it, and it will last longer, just like a car.

    What size O ring did you use, or did you just try some till one fit in there? I really like the idea.
  3. wrinkledoggi

    wrinkledoggi New Member

    OK well the clutch engages and disengages as it should, and with the lever pinned the bike pedals freely as it should. My problem is that the whole bike shudders and shakes when the clutch is engaged, and makes lots of whining noise. Will this adjustment proceedure cure that? For the inside of the carb cap I used a 5/8" O-ring from Ace Hardware, it was just enough to raise the slider inside so that there would be the right amount of idle speed adjustment - fit perfectly and worked like a charm.
  4. happycheapskate

    happycheapskate Active Member

    Yes. It sounds like your clutch is let out too "loose"/far. You are not getting full engagement. The instruction book with mine described this problem and said adjusting the clutch as described would solve the engagment problem.

    oh... on the "carb cap" I know what you mean now but we weren't talking about the same thing before. You mean where the cable comes in and the cap is hand tightened. I used teflon plumbers tape and it worked perfectly for sealing it. If you want to adjust it, there are 2 methods. The physical cable adjustment at the lever, and moving the C-clip on the needle inside the carb to change the "length" of the cable by mm. If you remove the cap and pull up the valve (note the orientation that meets with the idle screw on the tapered notch at bottom), you will get loose a spring, a silver c-shape washer, and a tiny tiny little black c-clip "packman clip" as the inst. worded it. You can move this clip along the needle to different notches to regulate the length. Do not lose any of the pieces or the carb will be dysfunctional till it is reassembled correctly. (do it over paper towels by taking the carb off.

    I thought you meant put the o-ring in the carb fitting where it goes on the inlet tube! hahaha.
  5. happycheapskate

    happycheapskate Active Member

    Ps you are supposed to pedal to take off then engage the clutch.
  6. happycheapskate

    happycheapskate Active Member

    The screw with spring on the carb is for idle speed adjustment. There is no mixture screw. (unless you got something way better with your kit! :)
  7. wrinkledoggi

    wrinkledoggi New Member

    by using the o-ring inside the carb cap, I didn't need to take all that stuff apart . . . . just the thickness of the o-ring was enough to raise the slider to an adjustable orientation, without all the hassle . . . . (I like easy over complicated)
  8. wrinkledoggi

    wrinkledoggi New Member

    I didn't mess with the mixture screw at all, didn't need to
  9. AussieSteve

    AussieSteve Active Member

    wrinkledoggi - I'm not sure where to start.
    Don't use the cable sheath adjuster to adjust your slide level for idle - a big no-no. Besides other considerations, this leaves no slack in the cable, so when you corner, your idle is likely to increase.
    The idle speed screw is there for setting the idle speed.
    The cable should have 2-3mm free play so that as you move the handlebars from side to side the cable doesn't tighten and open the throttle further than intended. (Can be great fun when doing a u-turn.)
    Also, once the engine is running, you don't necessarily need to pedal before releasing the clutch - depends on bodyweight etc. If you can take off without pedalling, go for it.

    The purpose of the 'C' clip is not to change the length of the cable by mm.
    The purpose of the 'C' clip is to make the (low to mid-range RPM) mixture richer or leaner by varying the amount of fuel relative to the amount of air passing the slide. ie. Raising the needle by one notch adds more fuel to the mix for a given slide opening.

    With the clutch shudder, it's possible that the problem is being caused by poor clutch adjustment, as suggested by happycheapskate, so check to see that it's engaging properly and that there is some free play in the clutch cable when the clutch is engaged.
    I would also check under the RHS side-cover and ensure that everything is tight.
    These things do vibrate quite a bit until the clutch is fully disengaged and you get up to speed. Riding too slowly, near walking speed, will labour the engine and cause some shuddering and chain snatch etc. They're a bit lumpy until they get rolling properly.

    ... Steve
  10. happycheapskate

    happycheapskate Active Member

    confirming information

    This is mainly for other readers of this thread who will have questions:

    I looked at the instructions again to see if I had told you wrong. This is a very simplified carburetor. Very nice. It does have a mechanism for adjusting the mixture across the normal speed range. see below.

    Your idea is fine, and basically simulates "cutting" the cable to a shorter length by the amount of the spacer/rubber ring. Good fix if it works and seals tight. But if you cannot adjust the cable length by the threaded fittings at either end of the cable (lever end or carb end barrel adjusters), it is pretty odd. But its possible that these things are made by the thousands (cables) and that one was just inside of or maybe out of tolerances.

    I agree with AussieSteve in that you should be careful that when you let off the gas, it idles down all the way, and that moving the bars doesn't tug the cable any. Have a good ride today!

    The instructions had pictures of the internal carb parts and it says exactly:

    The Air/fuel mixture screw (idle) should be preset at 3.5 turns counter clockwise from the totally closed position. DO NOT back off screw more than 4.5 turns or vibration may loosen the screw and cause it to fall out. <happy cheapskate notes, spare included in kit> If this situation occurs, stop engine immediately and replace mixture screw. If a more rich gas mixture is required you can move the jet pin "pac man" clip <c clip> to the next lower position notch.

    I just adjusted the idle screw to wear it idles smoothest and not too high. I accidentally moved the pacman thing, but I'm not sure how it changed it because that was on initial inspection and assembly. It seems rich in fuel, but isn't backfiring or blowing fuel out of the exhaust. I have only driven it about 20 miles if that much, so I will see later today how it will do with minor adjustments.

    Last edited: Dec 6, 2009
  11. AussieSteve

    AussieSteve Active Member

    Are we talking about the NT carburettor supplied with most 2-stroke engine kits? If so, there is no idle mixture screw, only an idle speed screw. This is not an Air/fuel mixture screw.
    From the above, it sounds like you're talking about a totally different carby. (or I am.)
    (Post a pic if you don't mind.)

    By now, poor wrinkledoggi must be totally confused.

    ... Steve
    Last edited: Dec 6, 2009
  12. happycheapskate

    happycheapskate Active Member

    post pic: ok

    Hi wrinkledoggi. I hope you are not confused.

    Perhaps Aussie is right and we got different carbs. I thought these things were pretty common or universal, but maybe I got an upgrade or variation.

    Picture to come (editing post after upload)[​IMG]
    Last edited: Dec 6, 2009
  13. motorpsycho

    motorpsycho Active Member

    throttle cable adjustments shoudl not be made at the carb cap OR by raising or lowering the slide c-clip. as aussiesteve pointed out, the c-clip is for adjusting lean/richness of the air fuel mixture. Throttle cable adjustments should only be made by the adjustor on the cable that is up by the throttle. like aussiesteve said, if you adjust it in any other fasion, your cable could become too short, and it will pull the throttle open when you turn the handlebars.
    by raising the carb cap the thickness of the o-ring you used, will change the air fuel ratio (richer) because you are pulling the jet needle out of the main jet the thickness of the o-ring.

    on my 48 c.c. i did not have to make any internal clutch adjustments. all my adjustment was made at the clutch arm by the length of the cable. when your clutch is engaged (clutch lever out) you should have a little free play in the lever / clutch arm. the free play will ensure that the clutch is fully engaged when you let the lever out. with the clutch lever out, you should be able to wiggle the clutch arm back & forth slightly with your hand.

    you do not have to peddle your bike to start the motor. normally (well, with me anyway) i just get a rolling start and pop the clutch. I NEVER peddle my bike, i just roll down the driveway and pop the clutch. the only thing i use my peddles for is the coaster brake.

    happycheapskate: once you get your motor running, the only way to tell how it's running mixture-wise (too lean / too rich) is by reading the spark plug. you will have to run it and check the plug. as i understand the correct way to do it is to ride the bike at w.o.t. and then kill the motor with the throttle held at w.o.t. pull the plug out and "read" it at the electrode. if it's black the mixture is too rich, if it's a silvery color it's too lean. tan is the color that you're after.
    Last edited: Dec 6, 2009
  14. happycheapskate

    happycheapskate Active Member

    It only has one screw. The internals include a "depth setting" of the needle (relative to the sliding air valve ) which is manipulated by setting a clip on the needle to change its positioning. I like the design.

    I used blue low strength loctite on the carb screw for a extra safety. you can still turn it but it won't rattle loose. I suppose a bit of plumbers tape or the home remedy of nail polish will work as well. Yes it still has the spring too.
  15. happycheapskate

    happycheapskate Active Member

    motorpsycho. Thanks for the tip. I thought mine is a little rich running because of the sound and characteristics of how it runs across the RPM range. (just used to weedeater carbs, but they usually have 1 or 2 mix screws, an idle screw, and 2 limiter screws).

    I think the clutch is maladjusted because its scraping a little when I pedal only with motor off, and when I pedal with motor idling, it speeds up a little.

    By moving the arm by hand, it still seems this way, so I will try a small adjustment to clutch.

    Its close enough for now because the screw is working for adjustment,
  16. AussieSteve

    AussieSteve Active Member

    Hi motorpsycho. I agree with everything else you said, except...
    Adding an 'o' ring or washer under the cap doesn't raise the needle. The spring still holds the needle firmly into the slide by pressing on the 'c' washer to hold the 'c' clip hard against the bottom of the slide. The needle height is identical in relation to the slide.
    Believe me, I have a fibre washer in the top of my carb for other reasons and it doesn't raise the needle.
    I've attached a sketch.
    On mine, however, the additional seal did make the mixture a little richer. The carb used to suck air past the top cap before I fitted the washer. (I tested with carby cleaner with and without the washer.)

    ... Steve

    Attached Files:

  17. Al.Fisherman

    Al.Fisherman Active Member

    " The Air/fuel mixture screw (idle) should be preset at 3.5 turns counter clockwise from the totally closed position. DO NOT back off screw more than 4.5 turns or vibration may loosen the screw and cause it to fall out. <happy cheapskate notes, spare included in kit> If this situation occurs, stop engine immediately and replace mixture screw. If a more rich gas mixture is required you can move the jet pin "pac man" clip <c clip> to the next lower position notch."

    This screw is misnamed if called a Air/fuel mixture screw. IT IS A IDLE ADJUSTMENT SCREW nothing more nothing less. The 3.5 turns is a good start to where it will set the piston for a idle that the engine will run. If you remove the piston you will see a milled surface cut into the piston, not to be confused with the alignment grove. This screws ONLY function is to limit the travel of that piston in the DOWNWARD movement only. By decreasing the travel of the downward movement you are letting less ambient air pass through the venturi. Thus decreasing the RPM. The mixture adjustment is done from within the carburetor and is done with the "C" clip. This is done by changing the position of the "C" clip on the needle. The closer to the top of the needle the "C" clip is the more the needle enters the jet, thus restricting both the fuel/air mixture. The pistons purpose is much that of a butterfly in a conventional carburetor.
    Other then sealing the carburetor from ambient air, it will take up slack in the cable...not much, but some. The thickness of the compressed "O" ring.
    Last edited: Dec 6, 2009
  18. AussieSteve

    AussieSteve Active Member

    Thanks Al.

    ... Steve
  19. happycheapskate

    happycheapskate Active Member

    Thats what I got from looking at the parts too. The people in China may not worry about being totally technical with the instructions (like calling the primer button a "tickle bulb". hahaha.

    Thanks for all the help on this forum, and for helping wrinkledoggi. I'm having a good time here and learning a lot. Good website.

  20. Al.Fisherman

    Al.Fisherman Active Member

    Steve....Very nice right you are. Actually if one takes the carburetor apart all this we are describing will/should become much clearer.