Freewheel Rebuild

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Freewheel Rebuild

Postby RebelRider.Mike » Mon Oct 28, 2013 4:36 am

I bought a set of Grimeca 17" rims from a fellow on eBay. He had sandblasted them in preparation for some project that never happened.
Well, they arrived with the freewheel still on, which was a bonus for me, but it turns out the freewheel was never removed for the sandblasting, so it had lots of grit inside making a crunchy sound when it turns.
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Given the rarity of these freewheels (I haven't been able to find one like it anywhere) I decided to take it apart and clean it up. It seems that very few people do this, and not much info was available that I could find on how to do it, so I did it anyway.

It turns out the hardest part of the whole project was getting the sucker off the rim. To do this I modified a Park FR-6 freewheel removal tool.
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This part has been done by lots of people, and the tool and modification info is pretty easy to find. I removed two teeth, and narrowed the other two from 8mm to 6mm.
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I also shortened the teeth a little so the tool would sit flush on the freewheel.
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The modified tool had a couple problems: It slides back and forth on the freewheel, and it likes to pop off when I try to torque it. Fortunately, I was able to solve both issues with a lag bold I found amongst the strange things laying around in my basement.
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It fit over the tool, and through the axle hole and the washer and nut went on just perfect on the other end. And for a few minutes, I even had a novel way to carry it around.
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It took a while to figure out how to get the rim to hold still so I could wrench that freewheel off. I thought of all sorts of things, but kept finding a lack of parts or tools to make it happen. I finally ended up sticking a 2x4 through the spokes to stand on, and butted one side up to an unfinished cabinet. That held it still enough to put some real torque on it without it moving much.
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A bit of extra leverage also helped:
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It finally broke lose, and was then easy to turn.
Just for reference, what I have is a 23-tooth, single speed, freewheel, made in France by a company called Atom. Or maybe that's just the name of the freewheel. Well, like I said, I haven't found anything like it on the internet.
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It seems most freewheel bearing covers have left-handed threads. Although, a few have standard threads. I started out assuming it was a lefty, and I got lucky. Of course, to keep everything from moving around, I had to put the freewheel back on the rim. A little tapping with a punch and hammer got it loose pretty easy.
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There is a pin-spanner tool available by Park to get these things open also; an SPA-2. But I don't have one, and the punch and hammer trick worked well just by light tapping, so its all good. Here is the freewheel with the cover removed:
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I had expected ball bearings to fly everywhere, so I put the freewheel in a bowl first. Well, they didn't fly; just sort of sat there. But there were 50 of them, and there small! So why take chances?

With the bearings out, and also a washer, (Or is it a spacer?) the spring and lever mechanism is exposed. This is really neat! I've never known before how these things work just by making some clicking sound.
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Lifting the sprocket off the center assembly, I discovered another set of 50 ball bearings underneath! Fortunately, these didn't move around much either, since I didn't have it in the bowl at this point.
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With all the ball bearings and the sprocket out of the way, that just leaves the center assembly. Which is obviously still full of sand and grit.
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The levers and springs were easy enough to remove. Although, as I'm now writing this up, I realize I've put the springs back in upside-down!
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The freewheel is now completely disassembled and ready for cleaning. The good news is that because the freewheel hasn't been used since the sandblasting, the grit inside hasn't caused excessive wear yet. And since I'm cleaning it all out, it won't in the future either.
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I used carburetor cleaner to get the grit and grease off. Then I used Krud Kutter to get the carb cleaner off. Water got the Krud Kutter off. My hands were filthy of course, so no pictures.

With all the parts clean and dry, I started by putting the springs back on the center assembly. Now you can see pretty clearly the springs installed upside-down. The shorter "arms" should be toward the inside, and the longer "arms" should be facing outside. After this writeup I'll have to go back and fix that...
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With that done, I put some grease on both ball bearing tracks on the sprocket to help the bearings stick in place.
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The 50 ball bearings are now in place. This part is a bit tedious, but tweezers help.
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With the bearings in place on the back of the sprocket, I put the center assembly down onto the sprocket, and it now holds the ball bearings in place. The whole thing can now be flipped over. I haven't installed the levers yet. They would stick out and make it harder to get the center part over the sprocket and bearings.
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Ok, now the levers are back in place. (At this point, I still didn't know the springs were upside-down.)
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Bearings and the washer/spacer thing back in place. I managed not to loose a single ball bearing!
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And then the cover goes back on. Early on, I noticed a "P" mark on the front of the sprocket, and no markings at all on the back. I used that to make sure I got it back together the right way.
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The freewheel now turns easy, has a nice sounding click to it. No more crunchy! I'll have to open it back up later and put the springs in right, but it seems to work fine the way it is. And maybe I'll add some grease to the spring and lever parts too while I've got it open. Maybe it won't need it. A lot of excess grease came out the seams during the first few turns. Perhaps its distributed itself well enough already. For now, I'm jazzed I don't have to try to replace this thing. Although if I had the part available, I would have replaced the washer/spacer thing. Its only as thick as a couple sheets of aluminum foil. And it was the only part that looked like it had any wear at all.
Mike

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re: Freewheel Rebuild

Postby Flat_Track_Racer » Sat Jan 11, 2014 6:35 pm

Whenever I removed a freewheel from my bmx I put the removal tool in a vise and turned the wheel. I rebuilt a couple freewheels after the spring inside wore out, putting the freewheel center piece in the outer piece had enough room to hold the bearings in place and I also used marine grease to water proof it somewhat.
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re: Freewheel Rebuild

Postby schwinnguy » Wed Jan 15, 2014 7:43 am

you can buy the park tools removal tool for about 15 bucks. and you can buy a new freewheel for about 15 bucks too. I recommend the acs claws. it is a chro-moly freewheel, and you can get them in many different sizes so that you can change your gear ratio. one good place to get them from is danscomp. and bicycle shop can order them for you too. I wouldn't try to save that one or use it. it's probably worn out.
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re: Freewheel Rebuild

Postby Flat_Track_Racer » Thu Jan 16, 2014 8:13 pm

Once they start skipping forward its time to replace
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re: Freewheel Rebuild

Postby schwinnguy » Thu Jan 16, 2014 8:45 pm

I would have replaced the freewheel in this post because;
a) they are so cheap to buy new.

and

b) the teeth on this one are worn out which means the chain is also worn and stretched.
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Re: re: Freewheel Rebuild

Postby RebelRider.Mike » Fri Jan 17, 2014 12:01 am

Flat_Track_Racer wrote:Whenever I removed a freewheel from my bmx I put the removal tool in a vise and turned the wheel.

That's an excellent idea. Use the wheel itself for leverage. I'll give that a try next time.

I've looked into new freewheels, but I have yet to find a 23T for less than $80. I would be interested in any sources you might know of. I get my parts mostly from moped websites. And eBay.
I've bought several Park tools from Amazon. I've been really impressed so far at Park's quality.
Mike

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re: Freewheel Rebuild

Postby schwinnguy » Fri Jan 17, 2014 5:53 am

a 23 may be hard to find on a bicycle site. the biggest is probably an 18. I use a lot of 16 on vintage bicycle restorations. the smaller you go, the more top speed you will have. as I suggested before, danscomp is a good place to start. porkchopbmx is another.
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re: Freewheel Rebuild

Postby Flat_Track_Racer » Fri Jan 17, 2014 5:57 am

When I raced bmx I ran 46 front 14 rear. Less teeth on the frewheel meant more speed. Why replace the old one with the same when you can get better performance with a smaller freewheel? Just a curiousity question.
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re: Freewheel Rebuild

Postby schwinnguy » Fri Jan 17, 2014 6:31 am

holy cow. 46/14? that is a tall ratio. I always used 44/16 or 43/16 depending on which track I raced at. the kids these days run a weird ratio of something like 21/12. I still race once a year at a nationals event at akron derby downs here in ohio. I still ride my 1982 skyway t/a in the vintage class. finished 3rd summer of 2012 in the 50 year old mens class. it's a blast.
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re: Freewheel Rebuild

Postby RebelRider.Mike » Fri Jan 17, 2014 7:35 am

I'm afraid neither of those sites has large freewheels.
As for why they need to be so big; keep in mind on a moped the primary use for the pedal drive is to start the engine. (At least, its that way on mine; other mopeds might be different.)
The smaller the freewheel, the more force needed to get the engine to turn over. Once the engine starts, the pedal drive's job is basically done. Unfortunately, that means the gear ratio is so close that pedaling the bike is just useless.
Mike

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re: Freewheel Rebuild

Postby Flat_Track_Racer » Mon Jan 20, 2014 1:52 am

46/14 with 185mm cranks
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