Clutch Spring Adjustment and Modification?

Discussion in 'Motorized Bicycle General Discussion' started by meowy84, May 2, 2010.

  1. meowy84

    meowy84 New Member

    Joined:
    Jul 18, 2009
    Messages:
    238
    Likes Received:
    0
    I'm getting my first engine ready for the initiall install. It's a PK80. I'll be doing the usual intake/exhaust matching and folloring some of the threads some light port work just to clean up the casting flash, etc. I'm also wanting to give the clutch some attention. My clutch was initially stuck from sitting in the box as so many others report so I took the clutch cover off and while depressing the clutch arm gave the pressure plate a slight whack with a rubber mallet which freed it up.

    Anyways, my first question is this: I'm not going to assume that it came properly adjusted from the factory so anyone know what the general pressure on these clutches should be at to prevent slip? Some have reported them being so stiff that the arm breaks. Since it was raining this morning and I didn't want to run out to the garage I decided to "scientifically" test this out in my livingroom (redneck, I know LOL) using whatever I could find, mostly new and full jugs of cooking oil for weights by hanging them off the clutch arm on the engine. rotfl Anyhow, it takes about 11 lbs of initial pressure to start the arm moving (and that's when I ran out of "weights") but I figure with another 6 lbs the clutch on my engine is fully depressed. So all in all it takes 17-20 lbs of pressure to fully depress/disengage the clutch on my engine as it came from the factory. This is nowhere near to breaking the clutch arm as some have reported. I suppose once I put the thing together and ride it I'll be better able to tell if the clutch is slipping or not and make some finer adjustments. But in the meantime I'd love to hear some inputs.

    Now, the second question concerns the actual clutch adjustment. I know there's a way to adjust the main clutch spring preload from outside the engine but I plan to disassemble the thing to grease the innards anyhow so I'll be adjusting the spring then.

    To illustrate what I'm talking about look at the front bicycle wheel. Once you adjust the preload on the bearings with the bearing cup there is another nut that you tighten against the bearing cups on both sides of the wheel so things don't loosen up. BUT WHAT ABOUT THE CLUTCH? Once the spring is adjusted, what actually keeps the adjustment collar from backing off a thread or two over time from the constant spring pressure on it and all the engine vibration since there is no lock nut behind the adjustmant collar to lock it in place? (see my attached amateurish illustration :) Manic Mechanic has a way better diagram). Mind you I haven't disassembled my clutch yet so maybe I'm missing something here.
     

    Attached Files:

    #1 meowy84, May 2, 2010
    Last edited: May 2, 2010
  2. meowy84

    meowy84 New Member

    Joined:
    Jul 18, 2009
    Messages:
    238
    Likes Received:
    0
    One more thing. What I was sorta trying to say is that I feel the clutch operation on mine is too soft as is. I don't have much faith in the quality of the friction material in these (probably just cork from cheap wine bottles that the workers drink at work LOL) so I want the clutch to have a nice grab. I always liked stiff clutches, gave me that subconscious feeling that they were actually clamping nice and tight with no slip. I'll also need a good grabbing clutch for when I want to give this baby that 50 shot of nitrous to overtake that little old man on his Rascal scooter.rotfl joking
     
  3. meowy84

    meowy84 New Member

    Joined:
    Jul 18, 2009
    Messages:
    238
    Likes Received:
    0
    No takers? :confused:
     
  4. GearNut

    GearNut Active Member

    Joined:
    Aug 19, 2009
    Messages:
    5,105
    Likes Received:
    1
    There are threads on how to adjust the clutch spring in Norm's help section.
    I think you all ready found them.
    There is no locking device to hold the spring adjusting nut in place. If you come up with one, please share it with us.
    I have read others suggest the use of an automotive valve spring as an alternative clutch spring. I have not heard of anyone actually doing this mind you.
     
  5. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

    Joined:
    Mar 20, 2008
    Messages:
    6,170
    Likes Received:
    18
    My best advice is to ride the bike BEFORE messing with the clutch! They are usually adjusted well right from the factory.

    BikeGuyJoe's signature is the best... "If it isn't broken, & you mess with it enough, it will be!" ;)
     
  6. corgi1

    corgi1 New Member

    Joined:
    Aug 13, 2009
    Messages:
    2,282
    Likes Received:
    1
    Does the thing that the clutch cable runs through (that screws in under the carb.) befor reaching the clutch arm lock the main spring adjuster?
     
  7. KCvale

    KCvale Active Member

    Joined:
    Feb 28, 2010
    Messages:
    3,890
    Likes Received:
    19
    The stay on the motor under the carb is adjustable, the little spring should be between that and clutch arm itself, the bigger spring is just a heat shield and goes on the cable between the lever and motor stay.

    With the clutch released (not locked on), and the stay screwed all the way in pull the cable tight and screw the brass cable retainer on it place tight as you can you can.
    20 or so clutch pulls will take out the slack.
    If you can lock the clutch on and roll the bike around your set.
    If not, twist the motor stay adjustment out or move the brass retainer up the cable more.

    When it's done you won't need more tension, the spring in the clutch plus the thinner return spring make it hard to pull in as it is until 100 pulls or so.

    If it gets too loose to disengage the clutch in the lock position, just twist the motor stay adjuster out some more like a hand brake.
     
  8. meowy84

    meowy84 New Member

    Joined:
    Jul 18, 2009
    Messages:
    238
    Likes Received:
    0
    Thanks for the input guys. Yeah I found Norm's clutch adjustment posts. Very good stuff. I guess once I assemble and ride the darn thing around and when it comes to a complete teardown I'll have a closer look and see if a little locking nut would be beneficial. But since it's not there no begin with maybe there's no need for it, maybe the collar that adjusts the main clutch spring tension doesn't back off from use. Time will tell.
     

Share This Page