Some help with centrifugal clutch install

Discussion in 'Motorized Bicycle General Discussion' started by geoldr, Oct 11, 2011.

  1. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Hey guys, so I ordered a centrifugal clutch today, and it already shipped. Should be here soon, its shipping from CA, and I live in CA. I'm looking over the PDF of how to install, and I'm a bit confused on two things. So here I will post the process that I think is right.

    1) Remove clutch cover.
    2) Remove retaining screw and flower nut.
    3) Remove small gear
    4) Install new clutch cover.
    5) Install clutch assembly.

    Seems simple enough. A couple of things that worry me though, is on the instructions it said that there are 3 pins that you are supposed to make flush.

    How do I do that? I don't have any tools like that.

    Also, by looking at this page:
    Motorized Bicycle Centrifugal Clutch Install

    And the guy there is saying to not forget to remove the shear pin. What's that? Do I have to put that back in when installing the new clutch?
    And reading other posts. People say things like
    "I machined away most of the taper on the clutch and also machined a keyway into it so that I could use the Woodruff key from the stock gear."
    I don't really know what that means either.
     
  2. chainmaker

    chainmaker New Member

    Joined:
    Jan 19, 2010
    Messages:
    2,597
    Likes Received:
    1
    cant help with the install but Im going to follow your install and see how it goes. Im thinking about putting one on one of My bikes
     
  3. GearNut

    GearNut Active Member

    Joined:
    Aug 19, 2009
    Messages:
    5,105
    Likes Received:
    3
    Shorten the 3 clutch pins... well you gotta do that or the new cover will most likely come into contact with the pins and things will get ground up badly.

    Beg or borrow an angle grinder of you have to.

    The shear pin in this case it the woodruff key. It is a half moon shaped piece of semi-soft metal. In case of sudden seizure of the engine or drive train the woodruff key is designed to shear and sacrifice itself before any damage occurs to the gear teeth or other engine parts. It also locks the gears to the shafts prevents the gears from slipping on the shafts.

    "Machined away most of the taper"....... No 2 engines or clutches are identical and the tapers of the shafts as well as the diameter may or may not match the taper and diameter of the shaft hole in the hub of the clutch. Most all will come close enough to work, but not all. Sometimes the clutch will need a little "massaging" to fit properly.

    "Machined a keyway".....
    The Centrifugal clutch does not come with a keyway machined into it to allow the use of the woodruff key. Most of the time this results in the clutch slipping on the shaft and this can do serious damage to both surfaces involved, the clutch hub hole and crankshaft. Some folks machine a notch into the clutch hub to allow a custom made "L" key to fit so as to lock the hub and shaft together and prevent any slippage between the two.

    silverbear has a good thread covering his experience with a centrifugal clutch and making a notch for the woodruff key.
    http://motorbicycling.com/f34/centrifugal-clutch-blues-17162.html
     
    #3 GearNut, Oct 12, 2011
    Last edited: Oct 12, 2011
  4. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Thanks for the response man. So, from what I understand, the crankshaft? has a notch for the installation of a woodruff key. But the centrifugal clutch doesnt. So what you have to do, is make another notch in the clutch and put the stock key in there right? And that's it? Because that's what I got out of reading the thread by silverbear, but you also mentioned an L key.
     
  5. rohmell

    rohmell Active Member

    Joined:
    Jun 2, 2010
    Messages:
    1,533
    Likes Received:
    0
    If there is a Harbor Freight Tools store near you, a rotary tool is an excellent investment plus, it's on sale, use a 20% off coupon and the price becomes $ 11.98.

    Professional 4 Speed Rotary Tool Kit

    All of my builds now come with a centrifugal clutch as standard.

    The first few centrifugal clutches I installed, I machined the keyway for the Woodruff key and it worked well, but was extra work.
    The last few builds, I have installed the clutch 'as is' with no problems.

    With new engines coming from BGF,the three clutch posts are already shortened to use with the centrifugal clutch.
     
  6. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Ok, I'll go down to harbor freight and get that tool. I can use that tool to shorten the 3 clutch pins right? I did not buy my motor from BGF. I got it new in box from a guy who sells them locally.No idea where he got it. Is there a way to measure the clutch posts so I know if I need to use the woodruff key? I'm still not exactly sure on how that works.
     
  7. GearNut

    GearNut Active Member

    Joined:
    Aug 19, 2009
    Messages:
    5,105
    Likes Received:
    3
    The L key is simply a standard woodruff key filed down on 1/2 of one side and poorly looks sorta like an L. Grinding a full groove into the clutch hub can be daunting to some and the L key is a workable shortcut to enable you to simply grind a short notch into the hub instead of a full groove. You need to patiently grind the notch and file the key a little at a time, checking the fitment frequently, to end up with a snug fit between the two to obtain the best results.
    As rohmell stated though, sometimes you get lucky and the parts fit well enough to forgo the key all together. This is a judgement call that the builder must make during assembly.
     
  8. rohmell

    rohmell Active Member

    Joined:
    Jun 2, 2010
    Messages:
    1,533
    Likes Received:
    0
    The only reason to cut down the three clutch posts is so that the replacement clutch cover does not hit them.
    When you get the centrifugal clutch kit you will see that I mean.
    Also you mentioned removing the flower nut, no need to do that if you are slow and careful when trimming down the three posts.
    When the centrifugal clutch kit arrives, I think everything will become clear.
     
  9. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Yeah that's what I think too. Why do you say that there's no reason to remove the flower nut? The PDF on the zoom bike site says you should, and it doesn't mention that you need to put it back on. So if I carefully trim the posts, I don't have to remove the flower nut.

    GearNut, you said that if the parts fit well there is no reason to have the woodruff key. How will I know if it fits well? Are there any measurements or something that I can use?
     
  10. rohmell

    rohmell Active Member

    Joined:
    Jun 2, 2010
    Messages:
    1,533
    Likes Received:
    0
    At the bottom of page 4 on that PDF it says to reassemble and adjust the clutch. If you put tape over the flower nut and retaining screw, then there is no need to disassemble.

    Also, do you have the clutch/gear pulling tool? You will need that to remove the small bevel gear.
     
  11. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Oh wow I completely missed that part. I see, ill just put tape then. Yeah I have the gear pulling tool, and i looked at videos on youtube to see how it works
     
  12. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Ok, so I purchased this rotary tool kit:

    [​IMG]

    And these two things:
    [​IMG]
    [​IMG]

    Hopefully the disks will help me cut the 3 clutch pins flush. And the other thing to make a notch.

    But do you guys know any way to check if the parts will fit well enough to be possible to not use a woodruff key?
     
  13. rohmell

    rohmell Active Member

    Joined:
    Jun 2, 2010
    Messages:
    1,533
    Likes Received:
    0
    Hold off on making the keyway until you see how the parts fit.

    Other members who had centrifugal clutches installed have had problems of the clutch slipping and machining away the taper, and then they had to do the keyway mod.

    I did the keyway mod on my first few builds to try and prevent any problems with the clutch slipping on the shaft.

    Eventually, I started to install them the 'normal' way, without doing any keyway cutting or anything, and they all are holding up fine, no problems at all.

    My opinion is to install the clutch normally, and if you eventually get slippage, then you can cut the keyway.


    BTW, my last two kits did not have vent holes up top in the gas cap, and those diamond bits were perfect for adding a hole or two up there.
     
  14. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Hey what do you think about using a locktite locking compound? I read that in the first thread mentioned. Bad idea?
     
  15. rohmell

    rohmell Active Member

    Joined:
    Jun 2, 2010
    Messages:
    1,533
    Likes Received:
    0
    The taper-fit friction has way plenty of locking force is the tapers are correct.
    Plus, the tapers are smooth, and fit together, the Loctite would probably get squeezed away from the surfaces that are contacting each other.
    Remember, you may want to disassemble the clutch for cleaning and regreasing the one-way bearing inside.
     
  16. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Honestly man, I don't even think I have more than 200 miles on this motor. I don't think I need to service the clutch yet. I rarely ride it, when I do it's mostly just around for no reason other than to show it around. And with a centrifugal clutch stops signs and slower areas like downtown are going to be much funner.
     
  17. GearNut

    GearNut Active Member

    Joined:
    Aug 19, 2009
    Messages:
    5,105
    Likes Received:
    3
    Any loc-tite (or any substance for that matter) between the clutch hub and shaft will ruin the physical ability of the tapers to lock together.
    Considering the real possibility that the tapers may not match up correctly, you can try loc-tite if you want to but I have found empirically that any material what so ever that can wear or compress over time will do so and the assembly will come loose. Usually at the most inopportune time like when you are in the middle of a long ride and far from help. A cel phone can alleviate this problem a little bit though.
     
  18. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    You're right, I won't use any material between the hub and shaft. The clutch should be here Friday, and I will be able to check the fitment. Hopefully it's all OK.

    After I shorten the 3 clutch pins, if I ever want to go back to using standard clutch, will I have to get a new clutch assembly? Or will it work?
     
  19. GearNut

    GearNut Active Member

    Joined:
    Aug 19, 2009
    Messages:
    5,105
    Likes Received:
    3
    The clutch will still work just fine. It will still work after you install the centrifugal clutch too, you just won't have much of a need for it anymore.
     
  20. geoldr

    geoldr New Member

    Joined:
    Jun 19, 2011
    Messages:
    260
    Likes Received:
    0
    Right. Hah, I knew that, don't know why I didn't put the two together. Now all I can do is wait for it to arrive and then check the fitting. In the meantime ill work on shortening the clutch pins. On top of all the other things I need to finish on this bike.
     

Share This Page