Centrifugal clutch blues

[silverbear]

In the words of the Greek play write Aristophanes, "If it ain't one damned (rhymes with rammed) thing, its another". I was out enjoying a ride on the 39 Elgin today when the automatic clutch started slipping. I limped the bike home and now it engages enough to accelerate downhill, but not enough to power the bike forward uphill or even on the flat. This motor has a few hundred miles on it and has been trouble free up until now. So what should I be looking at? I adjusted the clutch cable, but that isn't it. Darn, beautiful weather and I had figured on a nice long ride tomorrow. Guess not. Any tips will be much appreciated.
SB

 

[silverbear]

I've been looking at Norm's sticky on adjusting a clutch for slippage and am wondering if the procedure is the same for a centrifugal clutch?
SB

 

[AaronF]

Are you sure it is the clutch slipping? It may be the woodruff key is missing just like what happened to mine.

 

[GearNut]

There really are no adjustments on the cenrtrifugal clutches other than changing out the springs to affect engagement rpms.
I agree with AaronF, check to be sure that the woodruff key is still where it should be and that the nut is tight.

 

[corgi1]

If it is a china girl it may need the flower nut adjust or new clutch pucks

 

[corgi1]

If it is a 49 or 80 cc make sure the clutch cable is not too tight,,,as the pucks wear down the plate will move toward the clutch arm and cause the symptom of the clutch being partly pulled by hand thus slipping

 

[Rockenstein]

Silverbear search for my posts on the centi clutch, mine did the exact same thing until I modified the parts slightly with a Dremel so as to key the centi clutch's shaft adapter to the crankshaft. It has stayed put and been 100% reliable ever since.


edit: I think is the post I was thinking about...

http://motorbicycling.com/f4/does-centrifugal-clutch-require-pull-start-9877.html#post95601

 

[silverbear]

Thanks to all for the replies. I would think that if the woodruff key were missing it couldn't engage at all and it does accelerate downhill. Will check the nut. Cable is not too tight as I loosened it to the point it is barely doing anything. Rockenstein, I do recall reading your posts when they were written and will look them up for reference. I'll let you know what transpires.
SB

 

[silverbear]

I got the bike out to remove the clutch cover and noticed something. There appears to be a bolt missing as shown in the first photo. The second photo shows my other automatic with a bolt in the same spot. Could this be the problem? What is it for? Anyone know? I hesitate to just remove the one from the new engine without knowing what's up, but if there are no responses I guess that's what I'll do, make a trip to the hardware for another and see if that was the problem. Thanks in advance.
SB

 

[Rockenstein]

I would think that if the woodruff key were missing it couldn't engage at all and it does accelerate downhill.

As they come the centi kit's shaft adapter doesn't use a key. It's basically press fitted onto the end of the crankshaft and held in place with a bolt. If the bolt loosens the shaft adapter spins on the crankshaft and if it spun enough to machine itself or the crankshaft the press fit tolerances are machined away. Keying it is the best solution.

 

[silverbear]

As they come the centi kit's shaft adapter doesn't use a key. It's basically press fitted onto the end of the crankshaft and held in place with a bolt. If the bolt loosens the shaft adapter spins on the crankshaft and if it spun enough to machine itself or the crankshaft the press fit tolerances are machined away. Keying it is the best solution.

Is that the bolt missing in the picture I posted? If I were to replace it might that remedy the problem? So the woodruff key is only used on the manual models, is that right?
SB

 

[silverbear]

As they come the centi kit's shaft adapter doesn't use a key. It's basically press fitted onto the end of the crankshaft and held in place with a bolt. If the bolt loosens the shaft adapter spins on the crankshaft and if it spun enough to machine itself or the crankshaft the press fit tolerances are machined away. Keying it is the best solution.

How do you access that? Just remove the clutch cover (I hope). And how do you 'key' it? And is it too late for keying if the "press fit tolerances are machined away"? Thanks for being patient with me.
SB

 

[Rockenstein]

So the woodruff key is only used on the manual models, is that right?
SB

Yes the key is used on the kits that have the standard gears, on kits with the centrifugal clutch no key is used on the shaft adapter that I have seen.

How do you access that? Just remove the clutch cover (I hope). And how do you 'key' it? And is it too late for keying if the "press fit tolerances are machined away"? Thanks for being patient with me.
SB

Yes just remove the covers. You have to remove the centrifugal clutch itself to get the last half of the cover off. The crankshaft adapter on mine was hardened so when it loosened off and spun it machined the end of the crankshaft which of course machined the press fit tolerances away but I was still able to key it. To key it you simply grind a notch in the crankshaft adapter as shown in the attached picture. You might have to file away some of the key your going to use as your not going to be able to get an average sized grinding tool deep enough into the adapter so as to grind a notch that will allow a full length key to seat. On mine I'm using about 1/3 of the key to hold things in place and it's been good for 1500km or more.

I'll note too as I did in the other thread to pay attention to the length of the bolt that holds the clutch to the end of the crank. Mine was too long by a couple mm. Could be some cranks got drilled a bit deeper than others at the factory but do watch out for that possible problem.

 

[silverbear]

Thank you for your post. I see the hole you drilled.
Here is where I am in the dismantle... I have removed the bolts over the automatic part of the clutch and three bolts from the underlying cover. I assume there is a fourth bolt which can be accessed once the automatic clutch is removed. The pictures below show where I am at this point. I see that the spaces between the three segments are not equal and I also noticed that there are fine gray particles which I'm guessing are ground metal. I think what happened to yours is also what happened to mine. If I turn the automatic clutch by hand it moves the rear wheel, so I'm guessing that while some metal has been ground away, but not enough to spin freely. I suppose that is why it engaged enough to accelerate going downhill but was not tight enough to engage otherwise. Now, anything to watch out for in removing the bolt at the center of the mechanism? I figured to put a wide blade screwdriver into one of the spaces between the three large segments to hold it in place from turning as the bolt is loosened. Yes? With that removed the second cover should be accessible. I am aware that not all of these parts are made very well and don't want to break anything. Easy does it...
SB

 

[silverbear]

...back to the drawing board. I put the flat blade screwdriver in place, but that does not "fix" the clutch so that the bolt can be removed. It feels like the whole crankshaft moves and will require being held firm somehow or other. I read something about that somewhere here... was a rag involved in some way? Was one of the manifolds taken off? My memory bank has holes in the floor so that not all deposits stay put. Hmmm... doesn't look like I'm going for a ride today. How the heck is the crankshaft held in place?
SB

 

[Elmo]

...back to the drawing board. I put the flat blade screwdriver in place, but that does not "fix" the clutch so that the bolt can be removed. It feels like the whole crankshaft moves and will require being held firm somehow or other. I read something about that somewhere here... was a rag involved in some way? Was one of the manifolds taken off? My memory bank has holes in the floor so that not all deposits stay put. Hmmm... doesn't look like I'm going for a ride today. How the heck is the crankshaft held in place?
SB

pull your plug and stuff a piece of rope in on top of your piston and turn the crank till it stops. be sure to leave enough sticking out to pull the rope out. Also poke it in in a direction away from the ports. To get the rope out just back up the engine and pull the rope out. By the way i really enjoy your posts SilverBear.

 

[Elmo]

If the metal isn't too hard you can drill and tap a hole and use a screw for a key.

 

[corgi1]

If you remove the spark plug and feed in a foot or so of rope that should hold the engine while you take the bolt out

 

[corgi1]

you type faster than me

 

[silverbear]

Ahhh, ye old rope trick! I was close. 'Rag' starts with an R, too. I'll try it, time permitting this evening and otherwise in the morning. Thank you guys. I'll keep taking pictures and will let you know how things work out. It's an education!
SB