Centrifugal clutch issue

Agreen

Member
Feb 10, 2013
792
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Southeastern GA
So after a couple of years of searching, it seems that the HT cent. clutch has returned. I ordered one and am having the worst time trying to install it. Allow me to explain why:

First off, there are no instructions.

The drive extender does not fit the crank shaft. I tried polishing the crank a little with some sandpaper and crocus cloth, but the crank seemed too fat. I was able to tap it on some, but I got it stuck and i had to resort to a bolt, some vice grips, and a slide hammer to get it off.

The clutch cover does not fit. If I put one bolt in, none of the others fit.

The clutch cover is also so much thinner than the old one that it won't clear the manual clutch. There's about a 1/4" gap between the cover and case.

At that point i got a bit frustrated and put it back together.

Any suggestions?
 

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
How far off it is with one other bolt installed:



Here's how the cover sits with the manual clutch assembly installed (i did remove the whole clutch assembly for the first pic)



This is inside the cover, showing where the manual clutch hits.

 
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Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
Hmm...

I just went back and watched a YouTube video on installing the centrifugal clutch kit. His clutch gears don't extend that far out in to the cover. See the second pic above? Mine does.

Think that's the problem?
 

Agreen

Member
Feb 10, 2013
792
11
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Southeastern GA
After a bit of research, I found the issues are very common. I sanded and polished the crank some more while the engine ran without the small gear (make sure the woodruff key is removed). It still wasnt enough. So I heated the extension sleeve a little and threaded in a bolt to fit the sleeve. You don't want to tap directly on the end, that's where the clutch pads will go and you don't want to deform that spot. Tap on the bolt gently and it will go on without much force.

The clutch cover is about 6mm (approx 1/4") too narrow. That's why some were saying to use like 5 or so gaskets. That's ridiculous. Use the old clutch cover. Cut the face off and lap it on some sandpaper like you would a cylinder head. Makes a much sturdier spacer.

Hope this helps someone in the future!
 
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cannonball2

Well-Known Member
Oct 28, 2010
3,662
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Colonial Coast USA.
Look at your original cover it should be wider. I ran into this a while back. Some CGs have a wider driven gear and or position. This is common to my two GT5 style engines. I also have the auto clutch. I had no issues installing the driver. I did run it down carefully with my Milwaukee impact driver. I also Dremeled a small keyway into the driver, The driver locks by conical interference and shoudnt need a key but did it anyway. This clutch was on the narrower Flying Horse engine.

The clutch works well and the Sprague clutch is plenty strong for pedal starting. Its pretty cool having both clutches.

Back when I was experimenting with wet clutches this engine was my test bed. I must have removed the cent clutch 4or 5 times and finally never reinstalled it. I found it yesterday cleaning up and will reinstall soon. I like it!
 

rohmell

Active Member
Jun 2, 2010
1,533
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36
New York
I have installed dozens of these units. The trick is to slightly enlarge the tapers on the both the manual clutch assy. and the auto clutch sleeve. By enlarging the taper on the manual clutch, it will slide further down on the clutch shaft and then you will be able to use the supplied replacement cover with no clearance issues, and no gaskets will be needed.
I use a spare clutch shaft assy. and use a rat-tail file and slowly file material away from the manual clutch assy., and test fit until the woodruff can no longer be seen outside the taper, in other words it is fully contained within the manual clutch assy.
 

cannonball2

Well-Known Member
Oct 28, 2010
3,662
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Colonial Coast USA.
While I don't doubt you experience with the cent clutch rohmell, I believe the issue
is more likely with the gear cases. If you try to install the kit on the GT5 style engine there is a great difference in the engines/covers. The GT5 over is 17+mm while the cent clutch cover is 12+mm. This is why the common fix is to stack gaskets. Heres a comparison of the cent clutch cover vs a GT5.



My kit fit my older design FH engine perfectly with no mods(I opted for a bit of keyway).
Also this engine would not fit a recoil assembly because the crankshaft was too shot. These things are all the same but different.
 

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Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
Agreen said:
I just went back and watched a YouTube video on installing the centrifugal clutch kit. His clutch gears don't extend that far out in to the cover. See the second pic above? Mine does.
Thanks man, but I already watched it. It's probably the only YouTube video out there on how to install one. Also, in my defense, he never explained that the gaskets were to space the cover out enough. He only said to drill a hole for lubrication.

I get what both you guys are saying (cb2 and rohmell). I just don't feel comfortable with my machining ability to turn the crank or clutch shaft down, nor the inner diameters of the gears. I'd booger something up and it'd be all wobbly. And yeah, mine look the exact same. The new one is wayyy thinner than the original.

I think my solution of cutting the old clutch cover up to use as a metal spacer is pretty decent. Even if you just cut the face off, it still works. I could probably have gotten away with just drilling a hole for the clutch bell gear and bolted the new cover over it. Sure, it'd be extra wide, but that's what wide cranks are for anyway! Now that I think of it, I may just do that and post a how-to thread, since these kits are coming back. Also, have you SEEN the price of clutch cover gaskets? If you can find one not in a kit, it's like $3. If you need 5 or so gaskets, you're paying an extra $15 and waiting a week for some stupid pieces of paper! No thanks!
 

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
OK, so I got everything solved. Pictures will have to be tomorrow because it's too dark now...and I can't see straight after fiddling with this thing all day and part of the night.

So here's how I got it to work.
Step 1: you'll need a drill press and an angle grinder with a cutoff wheel. I drilled a hole in the old cover. It was somewhat centered, but whatever.
Step 2: run a bolt, lock washers, and a nut through the hole. Tighten it all down. Very tight.
Step 3: Chuck the bolt up in the drill press. No, we're not turning it on.
Step 4: mark where you need to cut the cover. Set the drill press base up so that you can rest the angle grinder on it, and cut at a constant height while you hand rotate the drill press.

Yes, it's janky. No, it's not the most accurate way of machining something. No, I also don't care. It came out great and that's all that I care.

So what I ended up with is a 1/4" aluminum spacer that fits perfectly, doesn't require waiting for shipping, and isn't all weird and squishy like a stack of gaskets.

No more getting my shoelaces caught in the clutch now. I have a cover over it!!
 

ZipTie

Active Member
Jan 8, 2016
750
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Mpls Mn
Good job on figuring all this out for us Agreen. Just another example of something that should be plug and play vs fiddle and diddle, but is very rewarding when one has triumphed over the problems these mods present.
I feel I may try this on a future build. dance1
 

Agreen

Member
Feb 10, 2013
792
11
18
Southeastern GA
Well, I really can't take credit for that. There are several threads here that address some of the similar issues. I think I've just experienced them all.

No pictures yet. I got dragged out to a birthday party today.

Something else that I need to show is the hardware I used. Maybe a video is in order.

The auto clutch is my favorite modification yet. Absolutely worth it if you can find one. (boygoesfast on evay currently has them)
 

Cgk_iii

New Member
Sep 5, 2013
23
0
1
San mateo
Hey where did you source your centrifugal clutch kit. I can't seem to find them anywhere. Hope I don't run into this problem once I do hehe
 

cannonball2

Well-Known Member
Oct 28, 2010
3,662
149
63
Colonial Coast USA.
The GT5 engine was a Grubee design. Its the one with the wider case. Seems these engines got copied and are quite common. The BGF clutches(I bought one) are for the narrow case engines and aren't going to fit with out a mod like Als(very nice!)or a stack of gaskets.

My point is Grubee has the centrifugal clutches that should be a bolt on for the GT5 style engine.

MZ Miami is now a US distributor and might be able to get the Grubee clutches. Just a thought.