bicycle engine tear down

Norman

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I jam a rag into the teeth of the big and small gear them loosen all the nuts on both sides of the engine. I use just regular sockets (metric) to remove the nuts. They will fit all the nuts with room to spare. If your won't you might have gotten a lame built one it happens mismatched parts
built by someone with a hammer.
 

Norman

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I don't have a crank laying around to do that. But to take it apart you need a press. I use a 12 ton press. You will also have to make or have some fixtures to use on the press. Using some heat on the parts will help them come apart.
When you put it back together heating up one of the flywheels and freezing the other half to shrink the crank pin will also help.
You will also need a flywheel truing stand of some sorts. So your in for a lot of work if you don't have the proper tools and could ruin the crank and flywheels.
 
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userix

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Jan 29, 2011
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Is it possible to remove the clutch internals by only removing the small chain drive sprocket? (i.e. pull out the whole internal clutch assembly with the large clutch gear and parts still attached and as one piece) I want to save the trouble of having to align the key, hammer the gear back on, put washer and nuts back on, etc. I notice a loose piece of metal (probably part of a washer or the likes in the clutch internal) is messing up the internal clutch area as I can see it through the cable stanchion hole. Unfortunately, I cannot remove the metal piece from the hole and would need to remove the whole clutch assembly.
 
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Norman

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you can remove the sprockets nut then drive the whole assembly out the other side. The bearing behind the sprocket will have to be driven out after you've knocked out the shaft with the clutch still attached. Both bearing are pressed up against a machined shoulder, so they come out on the same side they went in.
You will need to use a brass drift or some soft device so you don't damage the shaft. Don't beat the thing real hard or you will possibly break the engine case . You can remove the clutch with the same puller you remove the chain sprocket with. The puller is designed to remove all pressed on gears and the sprocket, except the magneto rotor.
putting all the parts back on is easy if you use super glue to hold the small keys in place if you have problems with them staying in place.
 
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rustycase

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Tnx for the great thread, Norm,

I did a clutch puck inspection and discovered the large ring gear that holds the pucks is quite loose with the pressure plate removed. Can it be adjusted with those two shims you mentioned?

I haven't checked condition of those 56 ball bearings yet... I had read this thread quite a while back, and recalled something abt them, but wanted to come back and re-read before I tore it apart... are there really 56 of them?

Tnx
rc
 

Norman

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Yes! Or more it's been a while since I took that fucter apart and I ain't kidding them things will shoot to the 4 corners of the earth.
I've taken some engines apart that have the shims, some don't so maybe one chinaman was trying to fix a f--k up, But if you have too much end play shims or a way to machine out the slop will help. Shims can be made or bought.
 

rustycase

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OK Norm, and Tnx! lol

When I was younger I'd just tear into stuff. I guess I am smarter now that I'm older. I got enough sense to ask before I tear things open! :)

I'll take it apart over a clean blanket and set a few of them hard-drive magnets real close to grab onto escaping parts.

Tnx for your advice... I still got performance issues with this little 48cc skyhawk, but I'd like to see that it's maintained to live through any improvements I'm able to make on down the road.
Wouldn't make much sense to ruin it with bad alignment at the primary reduction.
Best
rc
 

CJ5

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That is where the bearing should fall out. I tapped it a few times, feels solid. You can still see what is left of the rounded end sticking out. Usually the pin is what wears down (the pin is not worn down other than the impression of the bearing in one end), never seen it do this before. Any advise???
 

rustycase

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I looked at your excellent photo... great detail!

You have the 'bucking bar' ? ...the rod that normally protrudes a bit?

...and the ball bearing that sits in behind it is what has becomes pulverized?
It seems to me that I can see an imprint of the ball in the grease, down inside the hollow shaft! Are you sure the ball isn't stuck on the end of the bucking bar, or perhaps dropped off while it was extracted????
SOMETHING had to make that indent mark in the grease!

IMO, application of flame to heat something up for separation is a last resort.
I don't see any reason to do that, here.

From my limited knowledge of HT, there is nothing in there you can move, or depress without the mechanical advantage of the clutch release lever on the cover.... unless... you pop the clutch-side cover, and remove the flower nut and clutch pressure plate. Then you can see the actual clutch pads and the clutch rod the flower nut was screwed on to.

IMO it would be best if you used some solvent to clean out the hollow shaft, perhaps with some compressed air... see what comes out... use a rag when putting air pressure to it... gonna be messy!

Did you notice your clutch fail to work over some period of time?
...short, or long? ...as in, if the ball bearing in there was disintegrating?

...Unless there is something that has not been communicated... I would say clean it out and replace with new pieces, properly lubricated and adjusted and see if results are as they should be...

Theoretically, the only damage that could be done in there by disintegration of the ball is the rod ends could be worn, or perhaps a slightly wider spot there in the center of the shaft where the bearing sits.

It's an old, proven design, and not really too much that can go wrong with it.

Good luck !

I'd like to hear when you make some progress, or have further information.
rc
 
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Norman

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I haven't heard of the ball falling apart yet, I have heard of people loosing them when messing with the cover and the ball falls out with out the person seeing it.If the ball is in there using brake clean to wash out the grease then use a small telescoping magnet should get it out. Or just shove some grease in there install the short clutch shaft reassemble it and adjust the clutch. The ball is just a spacer that lets the spinning parts work with less friction. when that area gets dry of grease it will make an offal sound, you'll think the engine is coming apart.
 

CJ5

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Normally the bucking bar wears down. I can see what is left of the bearing. It looks almost like the bearing has melted into the shape of the shaft except for the a small bit that is sticking out. No it did not fall out when I removed the bar. I only discovered the problem because I was expecting it to fall out and it didn't.
I hadn't greased it in some time (probably too long). Maybe it heated up too much? I drive it 20 miles everyday. It has been getting louder lately over the last month. Should I tap it with a 3/32 punch pin if cleaning the area doesn't work. I am worried that it is stuck (somehow).
 

Norman

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The link below will help if you decide to tear into your clutch or the shaft, I've got the parts laid out and talk a little about the tear down. If you need more info look at some of the other stickys. You don't need to split the cases to take the shaft completely out.


http://motorbicycling.com/f39/adjusting-clutchs-spring-more-tension-8392.html
as long as the ball hasn't welded it's self inside the shaft you should be able to get it out. You might need to wash all the grease out as best you can . Use a hose on the flower nut side put the air hose up to the shaft and use compressed air to blow the ball out like a blow gun. Some tapping with a soft hammer might help and using a telescoping magnet may just pull it out. Swearing is optional, but will probably be necessary. You might be able to beak the ball loose if it's slightly welded in there with a slim punch. Taking the shaft completely out would be the last resort, but would be not that hard to do.
 
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rustycase

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May 26, 2011
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Dear Lord Vader,
If you find this information of value, perhaps you could include it with your excellent work?


This is a well run-in 48cc grubee skyhawk motor's clutch components.
As you may see, the pucks are rather well greased, and some are slightly burned. In use, the clutch functions very well.
My concern is with the internal clutch bearings not being lubricated.
Included is the reversible puller tool which works on all gears and sprockets on an HT china girl engine. It is inserted in the pinion drive gear, which I also pulled to inspect the seal behind it.

Pic #2 is the clutch face. I marked the steel bearing ring which is pressed onto the hub, retaining the bearings within and holding the whole assembly together.

Pic #3 shows where you may see the bearings, peeping out from the loose tolerances on this motor's clutch. I bought it used, and have no clue how many miles are actually on it. As you may guess, any grease applied to those bearings to prolong their life will be slung directly onto the clutch pads. This is a significant design problem that would be expensive to overcome, IMO.

Pic #4 shows the backside of the clutch assembly. The 3 steel dowels that run all the way through the hub are the ones the clutch release/pressure plate ride on. The 3 holes I have identified are my main point of interest here.

I am going to attempt dis-assembly by cutting off 3 16d framing sinkers to about 1/2" and set the assembly on a steel plate with the nails inserted into those small holes which will put them in direct contact with that steel ring on the opposite side. Then, with a large socket, I will press the center of the hub down, which should separate the ring from the hub and send my (56) lil tiny bearings all over the place for collection and lubrication, before re-assembly :)

Note: I do not own a hydraulic press.
First attempt will be using a large C clamp. Maybe three...
Next, I'll drag out my 8lb hand sledge and adress it once, with enthusiasm.
If these methods fail, I'll go visit a friend with a press.
IF #2: if the 16d nails bend, I'll use pieces cut equal length from an old drill bit, (using an abrasive blade), or perhaps a rusted allen key. Both these options should be harder than any nail.

ID of the steel ring is 45mm and OD is 60mm.
Pressing the assembly back together will optimally require a steel ring of that diameter, but perhaps 3 grade 8 nuts of the right size might do the trick... haven't yet got to that point...

More notes: Wear pattern on my clutch ring gear seem fine, and backlash with the pinion is OK, but I do show a wear pattern on the pinion that gives evidence the ring gear is wobbling. It is a bit noisy when pedalling any distance, with the engine running or not. I would NOT want to pedal it long.
rc
 

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Norman

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Some light oil on those balls will work, I wouldn't take that assembly apart,your going to need a press to get it back together. You may be able to do it another way, but this thing is a press together thing. Taking it apart will make it fit looser each time you mess with it. Some have taken it apart once got it back together again and then had it come all apart on a ride.
It's yours so you do as you see fit.
 

rustycase

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May 26, 2011
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Tnx for the head's up, Norm!

I'm kinda set on using at least a slight film of boat axle bearing grease on the balls, after inspection. I am unable to see any kind of oil holding up for the long run...

If there is any doubt about the fit of the re-assembly, I'll strike an arc a few places where the ring meets the hub to see that it doesn't want to come undone. The heat won't do it much good, but some grease is btr than none!

Best
rc
 

rustycase

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May 26, 2011
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Dear Lord Vader,
I hope you will find this information valuable for presentation in your excellent tutorial.


This is how I pressed the HT clutch hub bearing apart using a 3" HD C-clamp, some scrap steel plate, three 9 gage tico nails, and an 11/16" 3/8 drive socket.
I had blunted the nail tips on a grinding wheel. The process was done over a blanket on the saw table, with some HD magnets hangin around...

Pic #2 shows the result. The ring, pressed off the hub center/back, is the inner bearing race, and the clutch plate/puck holder/ring gear constitutes the outer bearing race. It was relatively EZ, and I can see where the possibility exists it shall never again be as tight as it was the first time, as Norm has said. This is NOT a proceedure that should be done unless necessary.

Pic #3 shows a head count of 52 3mm steel ball bearings which may be purchased from vxb.com or other vendors. 250 sell for $3.50 + the freight.
(ceramic balls are available for abt 30-40 times the price, if ur so inclined!)

SO, the question arises... How many bearings are really supposed to be in there, and would my clutch/ring gear run true-er with new replacement balls, OR, could I replace them with 1/8" balls to tighten up the clearance?

1/8" balls are .007" larger than the 3mm balls.

Another option would be to replace the ring gear, to tighten things up, but IMO there are no guearantees what tolerances might be in place at the HT factory on any given day. :)

I'm going to call the level of puck wear acceptable, and probably re-assemble with a very small amount of fresh boat-trailer grease on the bearings.

Best
rc
 

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