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Discussion Starter · #1 ·
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That is the question.

Whether 'tis nobler in the mind to suffer
the dings to the clutch drum from clawing the outer
pulley case in the effort...

Or to take arms against the crankshaft itself,
And by opposing upend the crank seal,
score the shaft surface, only later to find
a hidden set screw yet unknown.

To yank. To pull. No more, and by pulling to say
we destroy the entire centrifugal clutch in the
ignorance of how to remove it properly.

The heartache and the thousand natural shocks
of unexpected difficulties that ignorance is heir to.

'Tis a consumation devoutly to be avoided.

But hark... an MTF reader approacheth...

Hail, Hail, what say you to this dilemna?
 

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Most centrifugal clutches had a snap ring holding the sheave & drum portion to the "body" that contains the friction shoes--you'd remove the snap ring,then the sheave & drum assembly,then you would see the set screw(s) holding it to the crankshaft..then you loosen the set screws and if need be,use a puller,best to use a bearing splitter to pull against also,not directly on the body of the clutch..

Not all use this design,if yours doesn't then I'm not much help--I dealt with many "Comet" style clutches on my go-carts and mini-bikes in my youth..you may find an exploded view of your clutch on google images to help you see how its assembled..
 

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Discussion Starter · #4 · (Edited)
Most centrifugal clutches had a snap ring holding the sheave & drum portion to the "body" that contains the friction shoes--you'd remove the snap ring,
And this is exactly where I paused. As seen in my photo in post 1, I had already removed the snap ring, and found that the outer drum / double v groove (a singular casting, sheave), while able to freely spin (no resistance from clutch shoes), still would not slide off, even though it moves freely in and out axially, to the limit of the width of the shaft groove for the (removed) snap ring.

In other words, the clutch drum pulley will only slide "off" as far as the width of the snap ring groove. Then it meets a hard stop, which is the outboard "wall" of that groove. It will not slide off (by hand) beyond the outboard edge of the groove.

I have a theory about this, but I don't know enough about the topic to have any confidence in my theory... which is that the outboard wall of the snap ring groove has mushroomed a slight lip, from repeated rapid pounding against the circlip snap ring, where the snap ring might be made of harder material than the outboard "wall" of the snap ring groove it is beating against every crank revolution as the machine vibrates.

The best evidence of this "rotary hammer" action is that the entire centrifugal clutch assembly drifted out board off the end of the crankshaft.

Referring back to the photo above, notice that there is no crankshaft visible... the axial end is "recessed" within the clutch assembly by an inch, entirely out of view. This isn't by design. This is how I found it (other than my removal of the circlip) when I removed the belt cover. For a while now I had this premonition that the belts where out of alignment (one belt tight inboard on top, other belt tight outboard on the bottom).

After joining MTF, I noticed and responded to another member's post about her similar Kemp shredder, and then thought... maybe I should go ahead and check my belts too. This is what I found. The centrifugal clutch pulley walking itself off the crankshaft, with the only thing presumably stopping it being the all metal heavy gauge belt cover, which now had a slight bright circular witness mark on the inside indicating where the end of the drifting clutch pulley had begun rubbing.

Anyway, since I do not know all the different ways that the outer drum / double V groove casting may or may not be retained to the rest of the centrifugal clutch assembly, I paused after encountering resistance to separation by the elevated circumferential outboard "wall" of the snap ring groove that appears mushroomed into a lip that extends slightly greater than the diameter of the collar that the casting would otherwise seem to be designed to slide over once the snap ring was removed.

As you can see, I hit a "snag" on step 1, and thought I should seek advice.

then the sheave & drum assembly
While I haven't been able to remove the sheave and drum assembly, I have been able to tap it with an all rubber mallet all the way back on to it's originally designed position on the crankshaft (which was sprayed the previous night with Aero Kroil). What is interesting is the slight surface corrosion on the crankshaft in the formerly (and inadvertently) exposed area where the sheave and drum assembly are now homed again after the rubber mallet tapping.

then you would see the set screw(s) holding it to the crankshaft..then you loosen the set screws
THIS is what concerns me. That there are set screws in the inner clutch assembly collar that are only accessible when the outer sheave pulley casting is separated from the inner clutch assembly. THIS is why I am not yet satisfied by tapping the assembly back home. There is a reason it walked off the crank in the first place, and I want to find and redress the reason.

and if need be,use a puller,best to use a bearing splitter to pull against also,not directly on the body of the clutch..
Good idea on using two jaws on a splitter instead of 3 jaws on the part itself. Thank you.

Not all use this design,if yours doesn't then I'm not much help--I dealt with many "Comet" style clutches on my go-carts and mini-bikes in my youth..you may find an exploded view of your clutch on google images to help you see how its assembled..
I lost HOURS of life over the last couple of evenings watching YouTube videos of centrifugal clutch pulleys. Most of the videos dealt with parts that visually matched each other (sprocket drives) for go karts. None of the videos visually matched what I'm working with, or relatable in resolving the hurdle I encountered in step 1.

I've thought to fire up the engine, and touch a file to the "lip" to machine it down to the normal diameter of the rest of the central collar of the clutch assembly, but I can't act on a theory without first confirming whether or not the initial design of the central collar was intended to be the way that I found it.

The last time I had the belt cover off was 20 years ago, and my memory is a lot worse now than it was even then.

Speaking of missing brain cells... another thing MIA was a retaining end bolt on the end of the crankshaft, which has a 7/16-20 threaded hole in it. I went to the hardware store last night and bought a couple of different lengths of allen head capscrews, and will scrounge up a hardened washer of an appropriate inner and outer diameter.

On edit:

It turned out that my theory was correct. I applied a long strip of emory paper on the protruding stub shaft of the clutch collar, and right away saw that the protruding lip was became bright, while the remainder of the shaft still had the as found patina. I continued working the emory cloth around the shaft, and voila, the sheave slid right off with ease (no more "catching") once the "hammered" and "mushroomed" lip outboard of the snap ring recess was normalized to the collar diameter.

No hidden set screws inside the clutch assembly. The clutches look beautiful and meaty. Pretty good for a 50 year old clutch pack.

I've gone over the entire collar now with a ribbon of scotch bright padding, and will finish with 1500 grit strips of paper lubricated with anti sieze... all by hand. Earlier I had mentioned starting the engine... that was an overkill thought. And unsafe. There is some advantage to being slow to action, and long in thought. Eventually, common sense occurs to me.
 
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The bolt in the end of the crankshaft is sometimes all that retains a clutch or pulley,they dont put an set screws in the part,instead the keyway in the crank does all the torque transmission,and the bolt merely holds the clutch or pulley from walking off the end of the crank...replacing that missing bolt will solve your problem...might want to use a star washer or lock tite on it "just in case"...

Probably a good thing it was designed in a manner that the cover would keep it from coming completely off the crank under high rpms..
 
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