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Swan Offline OP
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After working on my primary chasing down a leak, I reassembled my clutch, primary chain and sprocket as normal, to factory torque specs and 1/2" of movement on the chain. I drove for about 10 miles and then heard a loud clattering noise and pulled over immediately. Trailered the bike back to my shop and finally opened up the primary cover to see this:

[Linked Image]
Broken clutch basket teeth.

[Linked Image]
Only a few survived. What happened?

As I took it apart, I checked the clutch and it worked, the tension of the chain was correct and the nut torqued correctly. The basket spins true and the alignment was correct after checking with a straight edge. Any ideas or suggestions?

I will wait to hear from the forum before I email Pearson. I assume the basket is no good and it will wear the chain quickly so it may be time to put the Goldie away for the winter until I get a new basket. But I need to know what went wrong before installing a new one. Bummer.

Last edited by Swan; 10/25/13 8:51 pm.

1966 Triton
1962 BSA DBD34 Gold Star
1966 Triumph Bonneville
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The chain was shot. All done. Buy a new one.
Have you tried the old side-ways hang-the-chain-in-the-air trick? D'you know of it?

Looking at the length of the 'slot' where each roller of the chain fitted onto the chain wheel, that 'slot' is FAR from round. In fact, it has become elongated, out of round, indicating the rollers were getting loose on the chain, increasing the wear on each tooth of the chain wheel, at the beginning and ending of the loop around the chain wheel, because of the uneven pull on the teeth by the loosening rollers on the bad chain.

I suggest you take a hard look at the engine sprocket next, are those 'slots' also now out of round?
If so, you WILL wear a new chain out faster than you'd like to... Maybe put unwanted extra wear in your new chain wheel of the new clutch basket?

You may have to replace both 'sprockets'.... Just to be certain your next chain lasts as long as possible?

..... May I suggest you ask the maker of your aftermarket basket, if they might be able to apply a new chain wheel to this, your "old" basket, instead of buying a whole new clutch basket? If possible?

That metallic sludge on the bottom of your case, with the bits of teeth rolling around in it, indicate to me the action of the chain links/rollers expanding around the length of contact around the chain wheel, indicates to me, the action was happening all along the recent break-in process.... Sorry to say...

Did I explain well enough so you understand what went wrong?
I'm never sure if I say things well enough with the words I use....
Brett

P.S. ... If you have a good strong magnet, apply the magnet to the sludge and see what happens?

Last edited by Rickman; 10/25/13 9:54 pm.
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The wear on the side of the teeth isn't indicative of aligned sprockets.

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Originally Posted by John Healy
The wear on the side of the teeth isn't indicative of aligned sprockets.
I agree (or, to rephrase what John wrote, the wear is indicative of misaligned sprockets). The same side loading on the sprocket caused by the misalignment that resulted in the wear also is responsible for snapping off the ends of the teeth. Unfortunately, it looks like it would be very difficult (perhaps impossible) to repair. Closer inspection of both sides would be needed to know better.

A repair to it would have to satisfy two constraints: 1) be unbreakable, because if the engine locked up it could kill the rider, and 2) not anneal the hardened teeth of the replacement sprocket.

That said, if it were the only one on a desert island where I had a lathe, mill, and TIG I would look into a combination of appropriate Al soldering alloys plus steel pins to attach an appropriate Al sprocket that had washed up on the beach. TIG welding certainly would anneal the teeth, but the tight control possible with a TIG torch on a low setting could work if an appropriate solder alloy with a reasonable melting temperature could be found. The sheer strength of the solder alone might be sufficient (in any case, it could be calculated ahead of time), but a few steel pins would make sure.

p.s. OK, I had looked at the photo on my iPhone on an airplane a few hours ago. Now that I'm home I looked at it again, and there's more to it than meets the eye. The base between the sprocket teeth is above the main clutch basket at the top of the photo, but is below at the left and right. We need a photograph of the other side of the clutch basket. Is the sprocket a separate piece from the basket? If so, this could be a very good thing.

Last edited by Magnetoman; 10/26/13 12:39 am. Reason: added p.s.
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I do believe the sprocket is a separate piece. I also believe the chain was too tight and may also be off on alignment. You can take a brand new transmission case and the holes are sloppy big time. So you think you had it tensioned correctly, but then just step on the rear chain and your primary is too tight. The holes in the transmission case are a sloppy 7/16" but you can put a 1/2" bolt much of the way in from either side. It is a known issue. The fixs is to either bore and sleeve the case or go to 1/2 bolts and open the serrated washers. Would also have to open up the bottom plate holes but not the top slotted hole, it usually is plenty big. Some guys have also put on a drive side adjuster.
Ron

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If your chain was not new when you fitted it, it may of had tight spots, thus you may of given the chain 12mm clearance at its loosest point.
Making the chain like a banjo string at its tightest point?
I too would like a pick of the rear of the chain wheel, I think the alignment looks out.

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Hi, All of the comments above are spot on.. We sell about 5 of these clutches each year and have never had an issue.. That being said, most are installed by us and Fitted with a brand new Regina chain, and the chain is checked often.. It sure looks as if your chain alignment is way off.. How thick are the shims that you have under the crank sprocket? We have found that one needs to add 60-80 tho shims under the crank sprocket to get proper chain alignment.. Also the Basket needs to be properly torqued to the main shaft, when checking alignment.. Not just pushed up snug..

Looking at the 3 clutches just received from Pearson, the Sprockets and baskets are CNCed from one piece. It would be
almost impossible to add a new sprocket only..

How old was the chain you were using, and had this chain and Clutch been in service for awhile?

Jake


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Yes I would also go along with the above comments, one other thought, is the basket centre bearing ok, it may not have much radial movement.
But there could be an excessive amount of rock on the basket. As the plates, when under pressure (drive) play no part in holding the basket in line.This would also give the same wear pattern as misalignment.
The early Pearson unit had a separate steel sprocket, and as Jake states the later ones have an integral aluminium sprocket.
Brian


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Here's an easy and common way to check primary chain alignment that's often overlooked.
With the inner primary cover removed fit the engine sprocket and compensator with the nut snugged finger tight. Fit the clutch chainwheel assy again finger tight. Clamp a long straightr edge or straight length of strap metal, I use a piece of steel strap, to the back side of the clutch chain wheel fitted against the inner edge of the engine sprocket. Shim behind the engine sprocket as required.

I strongly agree with Ron's suggestions of using over size bolts securing the tranny, correcting the OEM sloppy fit. Most racers and 'serious' road riders also add a drive side primary chain adjuster. A common method of properly adjusting the chain tension is insuring the adjuster is 'pushing' the tranny forward to deal with the OEM slop in the adjuster.

An older tuner once showed me how to insure the chains are adjust properly by running up the engine in 1st and pop the clutch with the front wheel against the wall. It works.

But.. A good belt drive sure works nice!

Last edited by dave - NV; 10/26/13 2:42 pm.

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The correct method of adjusting the primary chain is indeed often overlooked.
Here's the drill: Move the gearbox backwards with the tensioner, a little beyond the optimum chain tension, next, move the gearbox in forward direction untill the prim. chain tension is correct.


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Originally Posted by JakeH
Looking at the 3 clutches just received from Pearson, the Sprockets and baskets are CNCed from one piece. It would be almost impossible to add a new sprocket only..
If the clutch in Swan's bike is like the one in the following link, it looks like it would be fairly straightforward to machine a new sprocket replace the damaged one:

http://i170.photobucket.com/albums/...%20Star%20project/IMG_0198-Version21.jpg

Whether it would be worthwhile for someone without his own machining facilities to hire the work to be done depends on how much the clutch basket alone sells for. Pearson's site only gives the price for the complete assembly.

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Swan Offline OP
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Thank you all for responding. A quick note while I am at work and some additional (bad) images of the basket to say it is CNC'd as a whole piece, it does not have a bolt on sprocket. I will ring Pearson tomorrow and see if he will sell a just the basket. My stupid mistake for not double checking alignment after moving the gear box is going to be a very expensive fix and put the Goldie out for the rest of the season.
[Linked Image]
[Linked Image]
[Linked Image]


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1966 Triumph Bonneville
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Misalignment wouldn't cause that. something has caught between teeth and chain. Maybe a broken roller or sideplate.

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Originally Posted by Swan
I will ring Pearson tomorrow and see if he will sell a just the basket...
It's an unfortunate situation, but one that looks like it could be fixed fairly easily, and not too expensively. Assuming the back face of the clutch basket is ~1/4" thick, as it appears to be from one of the photos, the following crude drawing is how I would consider approaching it:

[Linked Image]

If this were mine I would:

1. install the basket in 4-jaw chuck and index off the bearing to get it Concentric to within 0.001".

2. remove the portion shown in cross hatch.

3. do the same with an aftermarket Al sprocket, except leaving the portion shown in cross hatch.

4. put on mill as a pair and drill/tap/countersink six 1/4"-28 screws. The ~1/8" remaining thickness on the back face would leave ~3.5 threads for each of the six screws.

5. screw together using John Healy's favorite red Loctite. Use epoxy between the two pieces as well, although the additional 10,000+ of total shear strength it would give to the assembly might be overkill.

6. drill and ream 0.001" undersize holes for six 1/4" dowel pins.

7. press dowel pins into place, again using John Healy's favorite red Loctite.

I probably would end up modifying the above somewhat if I actually had to deal with the problem, but I believe I could do all of the above and have a fully-functional, good-as-new, clutch ready to install in no more than 3-4 hours. A professional machinist would work faster so this job could cost less than $150, plus the price of an aftermarket sprocket. Depending on what you find when you talk to Phil Pearson, you might want to talk to a local machinist about your options.

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Swan: Your first post implies that this damage was done in only 10 miles. Was there no wear showing before the ride?

Gordo


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Magnetoman. Wouldn't you be better using an iron sprocket, what you loose in weight you may gain in strength and longevity.

Swan: was a belt option available when you bought this kit? Some of the decent makers out there like bob newby and qpd use a modern car grade belt as opposed to the rope cored nylon effort used on the more comercial kits. They are a lot less likely to snap too.


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Originally Posted by Allan Gill
Wouldn't you be better using an iron sprocket, what you loose in weight you may gain in strength and longevity.
It should go without saying that steel is stronger and would last longer than Al. However, the issue isn't that, it's whether Al is strong enough and would last long enough. If the answer to both of those questions is yes, then you would be better off using an Al sprocket.

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I have heard of Norton Commando rear brake drums being "re-sprocketed" by machining the old teeth off the brake drum and the center out of a new sprocket and shrink fitting the sprocket to the drum. I am not sure if it is also pinned or welded on in any way


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Originally Posted by geordie
I have heard of norton commando rear brake drums being "re-sprocketed" ...
This is what I will be doing with my worn Spitfire Scrambler's sprocket. First, though, I have to find where I have carefully hidden it in the garage...

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Swan Offline OP
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Thanks again everyone, here is another quick update with some better images, (busy, busy, busy work week). I spoke to Phil Pearson today, he saw the images on this post and believes it was a misalignment. He can fix the basket and offered to install a steel replacement sprocket so I sent it off today for repair. I am still unclear if the sprocket is separate from the basket, but the more I look at it, it just may be. I did not however remove the screws of the bearing retainer on the back to see if the sprocket is removable. I will have Phil look at the bearings to see if they are compromised too.

I will order a new primary chain just to be safe and Phil said not to use a a split roller chain and recommended a Regina brand chain. My current chain does not look bad and does not show any signs of wear, grinding, friction etc.
He also suggested using a board with some 6" nails pounded through it to help with the chain alignment (?) and after installing the primary chain to "run it up the road a bit and re-check the tension". As long is my bike is down for the rest of the short season (snow is coming soon) I am going to install new bushes on my high gear and the new main shaft seal/nut which arrived this weekend from SRM. It is nicely made and a good upgrade:
[Linked Image]

I will look through recent photos to see if there was any wear to the basket prior to this total failure. The drive sprocket is fine with no unusual wear on either side or the teeth. To refresh our memories, the clutch was new from Pearson, new chain and all performed fine for 2000 miles and then I removed the primary to install a new oil seal, buttoned it up with existing shims on the drive sprocket, ASSUMED the alignment was still good, moved the gearbox to the correct primary chain tension (1/2 inch total movement up and down), used ATF and it failed in less than 10 miles.

Thanks for all the suggestions, recommendations and advice. I'll need it and more when I put this all back together again with a new clutch basket. I cannot afford to screw this up again. Here are some better images of the carnage. Oh the humanity....

[Linked Image]
[Linked Image]
[Linked Image]
[Linked Image]
[Linked Image]
[Linked Image]

Last edited by Swan; 10/28/13 10:06 pm.

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1966 Triumph Bonneville
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Quick update: my basket is back from Phil in the UK and he did beautiful work as usual. The sprocket is separate from the clutch basket and is now made from steel.

As tempting as it is to throw this in and ride on what most likely will be the last ride of the year, I am going to wait so I can replace the high transmission gear bush and do it right. I'll ride the Triton instead.
[Linked Image]
[Linked Image]
[Linked Image]
[Linked Image]

Last edited by Swan; 11/14/13 9:06 am.

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I can just smell the hot machining oil in Phil's workshop...


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Phil P. did a good job, (as usual), you will probably be better off with this steel sprocket than with the former alu part.


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My only complaint with Phil's stuff is that it is way too "pretty" to hide inside the engine or primary...

Phil does nice work for sure..! Hope I get my next crank done pretty soon, want to put my Catalina back together..

Ron


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