Some help with centrifugal clutch install

G

geoldr

New Member
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.
 
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
 
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
 
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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.
 
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.
 
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.
 
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?
 
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
 
Ok, so I purchased this rotary tool kit:

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And these two things:
image_17639.jpg

image_10202.jpg


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?
 
Hey what do you think about using a locktite locking compound? I read that in the first thread mentioned. Bad idea?
 
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.
 
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.
 
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?
 
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.
 
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.
 
Ok, the clutch came in today. Unfortunatly I wasn't able to get any work done because my standard clutch started slipping. Ill have to fix that first, then move on to installing this one.

And just to be safe then sorry, id rather spend some time making a notch in the clutch and securing it with a key. Because if it slips and shreds the shaft, and I would have to replace that, that would be too much.
 
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I too just recently bought a centrifuge clutch and my first attempt to install I ran into few snags. After I grind the 3 clutch stud, it still rubs on the cover, so I had to order 2 clutch cover gasket for clearance. I also ordered rotary diamond bits to cut a notch on the new clutch and planning on using the old woodruff key. The other issue I had was my crank pedal was hitting the new clutch cover. I was told that I can bend the crank by using a long metal pipe. I put all of the original parts together and waiting for the gaskets to arrive before I make a 2nd attempt on installing the new clutch. I'll keep you updated and let me know how your installation went.
 
Wow your in a very similar situation as me. Do you mind taking some pictures of the notch you cut into the clutch? I'm having the clearance issue as well.
 
I haven't cut it yet, my rotary bits just came and I'm still waiting on my gasket before I cut the notch. Is your crank pedal hitting the new clutch? I'll try and take some pics and report back.
 
Oh ok. Yeah please let me know whats happening with your install, and ill post up on what's happening with mine. I'm having the pedal crank clearance issues as well. Hoping to just "kick start" it and ride around without having to pedal. I have no idea how to bend these mountain bike cranks. Maybe Ill just get a wide crank kit from SBP idk yet. Im going to cut down the 3 clutch pins today, and check clearance for that. Where did you get the extra gaskets?
 
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