The small cog is normally least affected by freewheel wobble, since lateral movement is caused by tilting. Also a bent axle shouldn't cause wobble. I would start by checking limit adjustments and hanger alignment and check if any of the teeth are bent more than they should be or have burrs.

Freewheel wobble can be caused by poorly machined threading on both or either the hub or the internal thread of the freewheel and the wobble can be slight to huge. In my experience older freewheels and hubs made for high end bikes before freehubs were normally accurately machined but nowadays freewheels are purely a budget offering and built to rough tolerances. However that said you should still be able to make the adjustments so gear changing is accurate it's just the adjustments are more critical than a freehub drivetrain. That is one of the big issues in that the cheap bikes need if anything the most skilled bike mechanics but people buying cheap bikes are often the most casual cyclists who lack those skills. When you buy a quality bicycle you can pretty much throw it together and ride within 10 minutes of opening the box but again a cheap bike might need a full service and adjustment before it rides well which could be a few evenings work. I guess my point is you have to up your game when dealing with freewheels and they aren't as easy to setup as a decent freehub based drivetrain especially if you have an example with excessive wobble.

You can check the lock ring/cogs to make sure they are tight on the freewheel body. If you don't have the tool, you can ask the forums to borrow one. Seek out pastor Bob. He can probably help with a diagnosis. What about the chain? I have had skipping problems before with a new chain/quick link. Also make sure the freewheel is not cross threading onto the hubs.

I'd say, 99% of freewheels out there have a wobble of some sort, in some degree, when freewheeling.
Pretty much, expected/normal.
I never experienced any sort of skipping from this wobble as chains are quite flexible by nature, so as to should not get affected, within the production tolerances that FW manufacturers leave on their product, short of the FW being totally non- functional.
I would suspect, other things with the drivetrain is causing it, like a worn chain stretch out of its service tolerance or stiff links on your chain or damaged teeth on the FW cogs...... maybe even a chain that is too wide for the FW cog spacing.

The wobble typically causes no problems. There's an outside chance it may be exacerbating the problem, but it isn't the root of it.

Skipping on the small cogs is the classic symptom of a worn out freewheel. BITD they were ridden until they started to skip, and then replaced. Typically you would go through two chains per freewheel, so this might be about 10-15 thousand miles. Shimano freewheels weren't long lasting, so I'd guess the lower end. Chain cleanliness makes a difference too. At any rate this is hardly surprising as mostly racers used things like Dura Ace freewheels when 6 speed was standard, and this one has likely seen many thousands of miles. The wear isn't usually visually observable. You can tell because the chain starts to skip.

AFA remedies: If possible, replace the offending cogs. That's what used to be done if the cogs were available and money was short. Probably hard to find now. Definitely check your hanger alignment, as a bent hanger can cause the same symptoms. Also check for stiff links in the chain. The problem might be minimalized by tweaking your axle position in the dropouts, if you have horizontal dropouts. Move the hub all the way back. Try adding a link or removing a link from the chain, or try a different chain.

Nothings perfect.. only with cassettes did the whole hub come from the same company, rather that 2 different ones. ..


being able to buy cogs was ending in back the 80's..

Since you mention that you didn't notice the wobble as this pronounced prior to trying it on these two sets of wheels, my guess is the retaining ring/outer bearing race is possibly loose. In my experience with Shimano 600 and DA 6 speed freewheels is that the plastic seal cover (what you see the printing on) and the retaining ring are basically hand tight.

The red Park two in spanner fits the holes on top of both. Remember this is threaded in reverse. First remove the plastic sealing ring. Then see how much play is between the outer and inner bodies by pushing them up and down. Basically there should be none yet the bodies rotate smoothly with only friction from the grease. If there is play, tighten until the play is gone and the movement is smooth. Install the plastic seal and tighten as hard as you can without damaging the holes.

There's a chance the smallest sprockets are worn. If you have two chain whips try to unthread the smallest sprocket The remainder slip on and off and are held by splines. Take pictures of the spoke facing side of the sprocket and post here for examination. BTW, I have a great supply of silver 6 speed 600 & DA small sprockets. PM me if you need further assistance.

Ditch that freewheel. It's skipping because the pawls that engage the axle are stripped out. It's shot. New 6 speed freewheels are a dime a dozen. Just make sure it's HG rated. Sunrace makes some very nice ones.

Sometimes a freewheel wobble is caused by a dork-disc that is seating only part way around the hub/freewheel interface, due to the hole in the disc being big enough to pass freely over the threads (i.e. too big to reliably self-center).
Ditch the dork disc (if present), if only to test for this possibility.
And try the freewheel on a different wheel, since Shimano freewheels typically show very good manufacturing consistency.

I've seen rear hubs that got bent between the left and right flanges, either from wheel impact or from careless spoke tensioning sequence.
Do the two flanges spin perfectly true(?), they should.

Are the bearings loose? (Like a wheel with the cones not tight enough? Can you move the FW with your hand with the wheel stationary? (Either side to side or tilting?) If this is happening, perhaps you can adjust the bearings. I've never worked on a Shimano FW and it has been 45 years since I did a SunTour so I have no idea if you can adjust the bearings or how you do it. Possibly you can back off the outside face and tighten the body or maybe there is a thin washer that can be removed or another added.

Edit: pastorbob beat me to it AND he knows Shimano FWs. Go to his post.

Ben

I don't like to be contrary and bicker with fellow members, but this is simply bad information. Pawls can't become "stripped out" and they don't "engage the axle."

Very, very, very, very--- rarely--- a pawl breaks (I've seen it twice in thousands of freewheels serviced). Other than the pawls becoming stuck in the closed position (i.e. the freewheel freewheels in both directions) due to old grease, too much grease, corrosion or other contaminant, they do not fail.

The pawls (which are attached to the inner body of the freewheel) do not engage the axle, they engage the ratchet teeth or notches on the inside of the outer body of the freewheel (however, with that said, Cyclo 64 and Competition freewheels do this in reverse).

If enough grit, or if a bearing breaks, or in the very, very, very rare case of a pawl breaking, the ratchet teeth or notches can become scored or even damaged. I always inspect them for damage and occasionally use a drum sander on the Dremel to smooth out a rough spot. However, I've never seen the ratchet teeth or notches "stripped out."

@Spaghetti Legs you don't mention if you've removed the sprockets and examined the back side which can't be seen while the sprockets are mounted (with the exception of the largest one). In my experience on Shimano UG freewheels is that the top side can look nearly pristine and never used, while the back side show significant wear. Unfortunately Shimano 600 and DA sprockets can't be flipped and run in the opposite direction.

If you are pressed for time, I have some 6 or 7 speed freewheels in that range you could borrow. I could send one out today. You would get it Monday or Tuesday.

​​​​​​​Pure class right there.

OT, what is the mood in Hooville after the mighty Zion Williamson shoe explosion? I'm sure they are happier than when the Grinch's heart grew 3 sizes.

wait a minute, you are using a record 10 chain on a dura ace freewheel ? I suggest you try another chain, I recommend a Sachs PC-850. The record 10 chains are narrow and since you report skipping on the small cog, that's probably the greatest chain angle out of plane with the cogs.

Do you have a way to check chain wear ? The Rohloff chain tool is excellent. In the pic below, the chain indicates "worn".

Lastly, if your freewheel is indeel "wobbling", it's possible that the body is worn or (maybe) defective. Someone above recommended adjustment of the internal cone, that's a good idea. Dura Ace freewheels (the MF-7400) were among the best ever made. I do have a supply of spare bodies, contact me off list.

Mark Petry
Bainbridge Island, WA USA

For certain a 10 spd chain could not be helping. I'm surprised that works at all. +1 new on a new PC 850.

FWIW, the generally held view in the freewheel era was that you should never put a used chain onto a new freewheel. Folk wisdom said: if you put a used chain on a new freewheel, it would wear it out prematurely. Therefore, when you got a new freewheel, a brand new chain went on.

+1 for checking the freewheel bearings. That's more wobble than I'd expect from a Duracce FW, even the early ones.

^^^^^ Or just swap in that low-miles 8-speed chain as a test, just to rule it out (or in).

Just to add to some of the previous comments. The Dura Ace freewheels were excellent and the body mechanism in particular was well made. If yours is wobbling, I would guess that it is a high mileage example and showing some signs of wear as they generally were well machined and would track pretty straight from new...It may have spent some point in its life un(der) lubricated and also may have had water contamination...I think this is an issue unrelated to the chain skipping. If the chain is good, it is almost a near certainty that the skipping cogs are worn. It's sometimes very difficult to determine by visual inspection. I wouldn't be surprised. As good as these freewheels were, their cogs didn't wear as well as those from Regina or Maillard (Sachs) which were VERY hard wearing..but everything will eventually wear out. I'm not sure I would track down cogs if the body is showing these signs of significant wear.

[QUOTE=pastorbobnlnh;20806906]I don't like to be contrary and bicker with fellow members, but this is simply bad information. Pawls can't become "stripped out" and they don't "engage the axle."

Au contraire mon frer. Very sorry about your inability to understand how freewheels work. Once the pawl system begins to break down they're toast. Chain skipping begins and just becomes progressively worse. Be good. Have fun.

Yeah, it's probably the chain. 9 speed and up aren't actually 3/32". UG cogs are a bit thicker and the teeth aren't as profiled. You might be able to get away with a 10 speed chain on HG but not UG.

BITD I'd change my chain every 1,000 miles. I was either working at an LBS or as a sales rep when I was putting in lots of miles, and remember getting Sedisport chains for $2.45 each if purchased in a 10 pack wholesale. I often gave my "old" chains to poor racers. I never wore out a cog.

I'm going to agree the narrow chain is primary reason for skipping.

Also agree that almost all freewheels wobble. One source of that is bearing races with not enough balls. It's a large diameter race that takes a whole lot of little 1/8" balls. If the races are filled completely the FW binds. Best operation is usually two, three, or four balls short of full. At the factory this is not done accurately and they are always way short of full. All the way back to 70s I opened my freewheels, greased them and added balls. Doing all that work did reduce wobble substantially. If it bothers you go ahead and open the FW. Everyone should try it once.