new bgf 80cc clutch issues

Discussion in 'Frame Mounted Engines' started by bigdaddyclint26, Jun 21, 2010.

  1. bigdaddyclint26

    bigdaddyclint26 New Member

    well on on my second build its an 80cc ht motor under the ebay name of boy go fast its a slant head 80ccand just cant seem to get the clutch to stick, what i mean is i have tried everything to get it to engage the engine whenlet go of the clutch arm. the plate just spins and does not turn over the engine i have pulled the plate off ruffed it up with tools taken brake cleaner to both pads and plate turned pads over tightend the plate and flower screw all the way in and still nothing there just does not seem to be enough push from the plate to the pads i dont know what else to do any help would be great. and it used to go when i first got it together about 5 days ago so i know it runs also when i pull the plug and let the clutch go it turns the engine over. maby there is to much compression.... i dont know im pulling my hair out over this one
     

  2. GearNut

    GearNut Active Member

    The main clutch spring that squeezes the clutch together is inside the transmission case, between the clutch and final drive sprocket. It is adjustable from the outside of the cases.
    1. Remove clutch cable from engine.
    2. Remove sprocket cover with clutch release lever.
    3. Remove clutch cable stop from top of transmission. It just unscrews after loosening the lock nut that binds against the top of the transmission housing.
    4. Find a strong flat bladed screwdriver that fits snugly down into the hole that the clutch cable stop was threaded into.
    5. The spring adjusting nut is basically a threaded collar with 4 notches, equally spaced, cut around it's circumference. The trick here is to rotate the final drive sprocket with channel lock pliers or similar tool that will not damage the sprocket teeth.
    Rotate the sprocket while pressing down on the screwdriver until you feel the screwdriver slip down into one of the 4 notches of the spring adjusting collar.
    Once the screwdriver fits into one of the notches, the sprocket and sprocket shaft should be difficult to turn.
    6. Hold the adjusting nut inside the cases stationary with the screwdriver and turn the sprocket clockwise to tighten the main clutch spring.
    Do not adjust is too tight as doing so will only make squeezing the clutch lever harder, strain the clutch cable, and accelerate wear on the clutch release components inside the cases.
    1/2 to 1 full turn should be plenty, but you may have to experiment a little (read do all of this over a few times).
    7. re-asemble everything back together, adjust your clutch cable and flower nut back to "normal", and enjoy a clutch that actually puts proper pressure onto the clutch pads.

    Note: You can rotate the sprocket by wrapping a length of chain around the sprocket and inserting a screwdriver in between the link plates on both ends of the chain to close off the chain "loop" wrapping around the sprocket. The smaller the loop, the better effectiveness this will have.
    Push down or pull up (not in and out of the chain) on the screwdriver to rotate the sprocket.
    This is in effect a poor man's chain wrench, a shade tree way to get the job done with out risking damage to the sprocket teeth.
     
    Last edited: Jun 21, 2010
  3. bigdaddyclint26

    bigdaddyclint26 New Member

    well i tried your directions and it seems that i cant get it to turn clockwise it seems to be all the way tight. i think maby the main spring broke or somthing shouldent i be able to see the thick spring move back and forth a little when i pull on the clutch arm that attaches to the engine? or is there a way to tell when it has broken? thanks for your help
     
  4. GearNut

    GearNut Active Member

    The spring is not really visible just by looking down the little hole in the top of the cases. You should be able to see the adjusting collar though. All of the moving parts are to the left (sprocket end) of the hole.
    Unless the threads are messed up on the collar or shaft, it should turn. You are only compressing a near equivalent to an automotive valve spring inside there.
     
  5. bigdaddyclint26

    bigdaddyclint26 New Member

    when i look into the hole i see the spring and i can push the bike back and forth and see it move around in a circle the problem i have is the black ring with the notches in it is so far to the clutch side thati can only fit a small allen head in there. when i try to put a socket on the end of the clutch side the one that holds the big clutch gear on and turn it clockwise all i get is resistance and no turning i tried counter clockwise to see if i could loosen it and pretty much cracked the little lip that holds the clutch cable to the engine there. any one got any ideas
     
  6. GearNut

    GearNut Active Member

    If the spring retaining collar is that far over then the spring is definately loose.

    When you get the collar locked with your allen wrench, do not turn the clutch or the clutch nut clockwise.
    leave them alone. They are on the wrong side of the engine to make this adjustment.
    Turn the chain sprocket clockwise. http://www.bikeberry.com/10-tooth-drive-sprocket.html

    I am sorry that the hole for the cable stop has cracked on you. This is the first time I have heard of it doing that.
    I would try JB weld to help reinforce the hole when you screw the stop back in. The only load that that hole gets is from the locknut on the cable stop and the pressure applied to the cable stop when the clutch is dis-engaged by the cable tension when the clutch lever is squeezed.
     
    Last edited: Jun 22, 2010
  7. bigdaddyclint26

    bigdaddyclint26 New Member

    ok well i got it turned the right way and it turned. it was all the way loose, but even after i have got it tight now the clutch still slips i know its tight because the clutch are is VERY hard to pull i put the flower nut all the way in and its still stipping... i just dont know what else to do.. does anyone have the link for the complete clutch setup like step by step i fear i am just missing somthing in the setup of the clutch i might be doing it out of order..
     
  8. GearNut

    GearNut Active Member

    If you do the "pulley mod" you can remove all strain from that now cracked hole.
    Just use the cable stop as a hole plug.
    http://www.motoredbikes.com/showthread.php?t=24182

    Your symptoms were all pointing to a slackened clutch spring adjustment and tightening it should have fixed your clutch problems.

    Ok, I am grasping at straws now.

    First straw: Are you sure that none of the woodruff keys on the crank gear, clutch hub, or sprocket shaft have not sheared. Also, if this is a brand new engine, it is not out of the question for the factory to have forgotten to intstall one of them. Stranger things have happened before.
    If one is missing, the related gear or sprocket can easily slip on the shaft under load.

    Next on the list of straws is, how loose do the clutch pads fit into the clutch ring gear holes? They all should just barely float in the holes. If they fit snugly or tightly they will not be free to move about correctly when the spring pressure is applied or released. Most have a ledge going around the outer edge. That ledge should NOT be there at all. Chalk it up to poor manufacturing quality control. You may need to use a razor knife and trim them to fit properly. Do not sand or file them! Nobody really seems to know just what exactly they are made out of but we cannot rule out that asbestos may be an ingredient. :eek:

    If I think of any more straws I will post them.
     
  9. Al.Fisherman

    Al.Fisherman Active Member

    Here the clutch spring is fully extended.
     

    Attached Files:

  10. bigdaddyclint26

    bigdaddyclint26 New Member

    just wanted to give anyone a heads up if you were helping me fix the issues i had with the bgf engine, I finally got it working i think it was a combo of a couple different issues that added up why my clutch was slipping the first was the clutch spring was loose from the factory so when i got the engine i had to tighten the flower nut all the way down to get any type of clutch catching. after two days of riding the pads were so rubbed away that they had a glaze over them. so to make a long story short i tightend up the clutch spring orderd new pads and did a whole clutch and flower nut adjustment. runs like a champ for now lol. BIG THANKS to all that helped. The most goes out to you GearNut your a saint.
     
  11. GearNut

    GearNut Active Member

    Congratulations! I am glad that you got it all worked out.
    The glazing of the friction pads due to weak spring pressure makes alot of sense. Good looking out!:detective:
     
  12. bigdaddyclint26

    bigdaddyclint26 New Member

    well im back after a couple of days of starting the dang clutch pads are slipping again. I have been doing some looking around and i had a few questions for anyone... the motor i got on this second build is a slant head style could this be an issue im guessing there is more compression on this new motor because i can woop the heck out of my other bike and that one has a like 2k miles on it. this slant head is just eating up my clutch pads. Has anyone tried the pull start for the ht engines and if so got a guide on how to install them. also i was thinking if i put a diff head on it i will loose a coule mph but i might just get the right compression so i can peddle start the **** thing. any thought would be great
     
  13. GearNut

    GearNut Active Member

    Your clutch is slipping again?
    I am beginning to suspect that something may be warped in your clutch assembly.
    The slant head is a higher compression design that other heads.
    Pull starts are easy to install. Bear in mind that you will need either a wide crank kit or the ability to bend your existing cranks.
    Some folks do not like the pull start on a high compression engine. They can be a real booger to pull.
    Something with that engine is definitely weird, other folks do not have nearly the problems that you are experiencing with a slant head engine.
    Perhaps you accidentally got a 4 HP prototype?:D
     
  14. Al.Fisherman

    Al.Fisherman Active Member

    As far as experimenting with the compression, and lowering it, just add a head gasket..one at a time, unless you have a spare laying around. My 80 came with two head gaskets installed.
     
    Last edited: Jul 9, 2010
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