Clutch Clutch Camshaft Modification

Discussion in 'Transmission / Drivetrain' started by Fabian, Jan 31, 2010.

  1. Fabian

    Fabian Well-Known Member

    I've made this modification to the clutch camshaft and clutch lever tension has dropped significantly.

    This was not the reason for the modification though.
    I was seeking much better clutch modulation as in standard form it was almost impossible to get a good range of clutch lever movement from the point of disengagement to fully engaged.

    The clutch was either "ENGAGED" or "DISENGAGED"

    I wanted a progressive spread of engagement over at least half the clutch lever movement, allowing me to feed in the clutch at much higher rpm for faster getaway's from a standing start.

    Over a period of time grinding away the clutch camshaft, i realised that the engagement point on the camshaft needed to be moved closer to the centreline allowing more lever travel for less overall clutch throw.
    With these Happy Time style engines there is only about 2mm of throw at the clutch plate from fully engaged to fully disengaged, yet there's about 8mm of throw available on the clutch of which 6mm is doing nothing at all.

    All the modulation needs to take place in such a small window of about 2mm - a very bad design.

    I've achieved much better modulation with this modification, moving the contact point of the camshaft inwards by approx 2mm.
    Now i can feed in a reasonable amount of revs and have a nice progressive take-up over a reasonable range of clutch lever travel.

    It's taken me 3000 kilometers of being seriously irritated by such a useless clutch to do something about it.
    The image on the right needs to be flipped over 180 degrees as it's the right hand side that needs to be ground away.


    Attached Files:

    Last edited: Jan 31, 2010

  2. AussieSteve

    AussieSteve Active Member

    I posted a similar thread a few weeks ago, in 'Frame Mounted Drive Trains', here.
    One thing to watch with this mod is that if you take too much metal off the side of the cam, the clutch can lock in the disengaged position.

    ... Steve
  3. Fabian

    Fabian Well-Known Member

    I guess it's two brains working independently to achieve similar goals.
    In my situation i was chasing clutch modulation rather than friction reduction.

    Rich is probably a man who can lend his ideas to my sketch for an even more progressive method to get better modulation.

    The best bike i rode that had truly excellent clutch modulation was the Suzuki DRZ-400.
    You pulled the clutch in 10% and received 10% clutch slip, pull it in 30% and there was a perfectly progressive reduction in clutch force; continuing on through the clutch lever stroke - i was tickled pink at how good it was!


    Attached Files:

    Last edited: Jan 31, 2010
  4. AussieSteve

    AussieSteve Active Member

    I wanted both more feel and lighter operation - got both with my mod. I'm happy.

    ... Steve
  5. Fabian

    Fabian Well-Known Member

    I've got similarly good results but it's not perfect.

    There's a modification for a roller system to route the clutch cable to the clutch arm.
    It couldn't be that hard to modify the roller for a rising rate mechanism as per my diagram.
    A side benefit of using a roller mechanism is the potential to engineer an auto lock-out instead of the lock-out pin on standard clutch levers supplied with the kits.
    Pull the clutch in 3/4 and it auto locks - pull the clutch in all the way and the lock-out automatically disengages.

    I guess it's another project for another day.
    Last edited: Jan 31, 2010
  6. arceeguy

    arceeguy Active Member

    Just a thought, but I don't think the clutch in a HT was designed to be "slipped". I think that it is designed to be "on or off".
  7. Al.Fisherman

    Al.Fisherman Active Member

    I find that using the mod of the roller system, there is no need for anything else. With the roller I made the amount of pull on the clutch handle went from disgusted, (the angle of the cable through the engine valley guide), to under a 6# pull. I tested this with 6# mono fishing line.
  8. Fabian

    Fabian Well-Known Member

    arceeguy, i agree with you.

    Having said that there have been a few nervous moments where i've been at a T-intersection and needed to pull out as quickly as is safely possible.
    More than once i've had the engine stall on me because of the on-off nature of the clutch and usually under circumstances where stalling the engine wasn't helpful.

    I consider it a safety feature for the clutch to work properly, and for the few times i need to slip the clutch, in making a fast getaway, clutch wear will not be significant.

    Last edited: Jan 31, 2010
  9. stealthc9

    stealthc9 Member

    why dont you just learn how to slip the clutch? I never have an issue stalling. ANY clutch can be slipped. If you like I can see about making a 10min video of me riding my happytime cycle and not having one issue, start stop, slow start, quick start.
    I re;ease the clutch to shut my engine down, I dont use a kill switch. I burnt out too many cdi's with faulty kill switches.(only one on my bike but on my gopeds and pocket bikes too)

    Its just like riding a motorcycle. Riding with the clutch on this from a dead stop is no different then riding from a dead stop on my ninja. **** you can even do clutch wheelies with these bikes.

    One thing tho, I do like your modifications
  10. dinoseer

    dinoseer New Member

    If I have this correct, you are grinding a tiny bit on the leading edge of the bottom of the actuating lever the clutch cable connects to that pushes on the front chain sprocket assembly?
  11. Fabian

    Fabian Well-Known Member

    That's correct