What is this?

Can anyone identify what this retainer goes to, please?

Drive chain split-link.

it was probably holding your cam chain together was it?

it was probably holding your cam chain together was it?

Click to expand...

Well, could it go somewhere else? My final drive chain broke on me the other day, causing great shock and awe. It caused damage to the inner primary case, but as far as I can tell it's only the external part of the case that keeps grease from slinging everywhere. It doesn't appear to have broken through to the inside of the case, thankfully.

Anyways, I opened the primary case to assess the damage for this, and as I was intending on installing a new Sparx alternator anyway, this just hastened the process. I assume it comes somewhere from the primary? I haven't been near the cam chain.

And I'm making the assumption that this wasn't a piece of the final drive chain itself, but maybe it was??

It sounds like it is the lock clip from your master link (split link) in your final drive chain. If you hold it up to the chain you can see how it would fit.

I went for the scariest option first,your primary chain must have a joiner in it, or is it the reason your rear chain broke

You're probably right. What happened, I believe, is that the chain rubbed the chain cover, (I saw evidence on the outside of the chain) and caught the keeper pictured above. The odd thing is that the keeper itself resurfaced in my garage, while the chain flew out on to the road. Like I say, odd, but I've seen stranger in my line of business, I guess. I ordered a new chain yesterday, and I suppose a new chain cover is in order, too. The cover is turning into a real POS, needing a spot weld from before, and now cracked at the other end by the torque of the chain flying off.

Two weeks ago I was pricing a basket case to make a long term project, and I guess she got jealous, coz ever since I've been chasing repairs on her...

One time my master link came off on the hiway a few miles from anything but bush. I walked back and retrieved the chain and found the master link but couldn't find the end plate nor the circlip (in your pic). I was able to put the main piece in and tighten the chain to the point where only the tension held it all together. Then shifting ever so gently I made it about 2-3 miles to a metric bike shop where I bought a complete master link.

slupdawg said:

What happened, I believe, is that the chain rubbed the chain cover, (I saw evidence on the outside of the chain) and caught the keeper pictured above.

Click to expand...

The spring clip should always be fitted so that the closed end faces in the direction of normal chain rotation to prevent that happening.

L.A.B. said:

slupdawg said:

What happened, I believe, is that the chain rubbed the chain cover, (I saw evidence on the outside of the chain) and caught the keeper pictured above.

Click to expand...

The spring clip should always be fitted so that the closed end faces in the direction of normal chain rotation to prevent that happening.

Click to expand...

I noticed that even a plain 530 chain doesn't leave much clearance when the chain has a split master link. My primary inner case was also damaged by a broken chain in an earlier life (I assume from a broken gearbox, as its stamped with a '70 or '71 750 number). Most of the top of the 'brow' is broken off, almost flush with the case. I fashioned a sling guard out of aluminum, mounted to one of the Z-plate bolts. This guard covers the chain from the chain guard on the swing arm to where the brow is still left. Only an occasional spot of chain oil lands on the crank case. Without this sling guard, the whole left side of the engine would get pretty greasy.

I don't know how the clip made it inside your case, as the only way would be to somehow work its way through the felt seal. Perhaps it stuck to the outside of the case, held in place by the grease on the clip, and fell into the case when you took the cover off.

As to the rest of the link, it probably landed somewhere on the bike when the chain came apart, like on top of the swing arm by the horn, and just happened to fall off in the garage as you were moving the bike around.

Even the prototype Commando did that while we were testing. We were using a 3/8 inch chain (dumb!), smaller than the Atlas, even though the engine was the same. I was running about 105 mph on the test track at the time.

It didn't damage the chain case, but the engine was turned into an instant boat anchor. Bent valves, head damage, one cracked piston, ong completely destroyed piston and one con-rod out through the side of the case.

We retrieved the chain off the trackside and found that the split link had actually had the pins bent away from each other by the force of driving the bike at high speed. It looked the the Greek "pi" character.

We should have known the chain was a weak spot, as we were having to do an adjustment every two tanks of gas on the high speed testing. It was all the grief of keeping the alignment straight on that test series that resulted in the eccentric swing-arm pivot for chain tension adjustment that was designed for the AJS Stormer.

the engine was turned into an instant boat anchor. Bent valves, head damage, one cracked piston, ong completely destroyed piston and one con-rod out through the side of the case.

Click to expand...

Thankfully this was a low-speed affair. Just a few minutes earlier, I was going much faster. Could have resulted in more damage, or a skid. Lucky all the way around. I'll definitely be checking clearance on that new chain.

I think the person who had my bike before me had a chain experience. I always used to keep a master link in my toolkit and this bike came with one too. It could help you limp back.
These days I guess most of us would just call road service though.

Keyring, key fob

I don't have a picture, but a spare master link can be used as a keyring or key fob. As long as you have your keys, you will have a spare master link of the correct size.

Jean

One of my old bikes, an Ariel Leader, had a totally enclosed oil-bath drive chain case. Talk about over-kill - it was only a 250cc 2-stroke!

I tried to get N-V interested in putting an enclosed case on the Commando. I even designed a three-piece job that used aluminum square tube and a couple of elastomer bellows. After our experience during testing with the thrown chain, I thought it would be worthwhile. Got shot down because it would've cost nearly $3 to make!

Unfortunately I don't have my old design notes for that. There might be a market for it in the restoration business!

frankdamp said:

One of my old bikes, an Ariel Leader, had a totally enclosed oil-bath drive chain case. Talk about over-kill - it was only a 250cc 2-stroke!

I tried to get N-V interested in putting an enclosed case on the Commando. I even designed a three-piece job that used aluminum square tube and a couple of elastomer bellows. After our experience during testing with the thrown chain, I thought it would be worthwhile. Got shot down because it would've cost nearly $3 to make!

Unfortunately I don't have my old design notes for that. There might be a market for it in the restoration business!

Click to expand...

I was talking to a local guy who is restoring a 1935 Marston Sunbeam. He said one of the distinguishing features was the enclosed oil bath chain. He stated chains lasted a really long time, especially in Palestine, where he spent his youth.