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'O' Ring Rear Chain

A review of correspondence from NOC-L

A modern 'O' ring type chain would seem to be an obvious modification for a Commando but it is not straightforward to fit


Ideas for fitting an 'O' ring chain

I was wondering about going to an 'O' ring chain. It seems that the only way to do it is to go from the 530 to a 520. The problem is that I can't find a countershaft sprocket in a 520 that is the 22 tooth that I want.

The inner primary cover seems to have the room needed for a 530 'O' ring, but the chainguard back by the shock doesn't. Well, I've been going through my mail and noticed Knut's post on 29 tooth engine sprockets. Is this a new item? I can't find it in my 1-98 catalogue. It's hard to read with the pictures superimposed on the text. This would be great: go back to a 19 tooth countershaft 520, turn the rear sprocket, get the 'O' ring chain, then up the ratio at the engine. Would there be any clearance problems at the pillars cast into the inner primary for the stator studs?

Bob Patton (bpatton@humboldt1.com) on NOC-L 14th. Feb 1998


Adjusting the clearance for an 'O' ring chain

I bought a D.I.D. 'O' ring type chain and installed it on the bike. I did notice a clearance problem right off with the master link, where the ends of the pins protruded far enough to make contact with the round steel plate on the inside of the primary chaincase counter shaft. So I carefully ground off a little material from the ends of the pins, but not enough to disturb the groove holding the keeper.

That was enough to give me clearance at the primary chaincase and I've been running the same chain ever since, for about 12,000 miles without an incident. All I do for maintenance is occasionally spray on an 'O' ring chain lube to keep the rings flexible and protected. The factory grease stays in. This chain was designed to withstand the power of the big bore Kawasakis of the time, which were notorious for eating up the standard issue for lunch. You might want to try one of these.

Bill Larson (william_larson@aar.com) on NOC-L 1st. Feb 1999


Method for fitting an 'O' ring chain

The 520 'O' ring swap is relatively easy. First replace your 5/8" x 3/8" (530) transmission sprocket with a 5/8" x 1/4" (520) sprocket for a 1964 and earlier Dominator twin. These should be available from any shop that sells parts for the pre-Commando models. I get mine mail order from RGM Motors in the UK. 15-23 teeth are listed as available in the catalogue.

Clearance between the Commando chaincase and transmission for the drive chain will vary but most will not have room for modern 530 'O' ring chains. So you will need to have a good used or new rear sprocket/drum reduced in width from 3/8" to 1/4". I have a shop with a good machinist here locally that does this for about $25.00. Take the metal off the outside. I haven't tried it, but I think this could also be done with a MK3 style sprocket if necessary. Also if you have an early Commando with the bolt-up style sprocket/drum, I suppose you could simply use the pre-1965 sprocket/drum/sleeve nuts and save the cost of the machining process. The transmission sprockets are more difficult to machine because they are hardened.

I have used both RK and Tsubaki 'O' ring chains and they last 17,000 - 20,000 miles at which point the sprockets are also toast. They will rarely need adjustment until the 'O' rings are shot and the grease inside works its way out and onto the rear tyre and rim. Both 520 'O' ring chains were the same width as several 530 non 'O' ring chains that I compared them to many years ago so you shouldn't have a clearance problem. Tensile strength was also comparable. If you are concerned with strength, consider that many modern bikes which make a lot more horse-power, including the current Ducati 750-900 models, come as standard with 520 chains.

If you cannot live with a fraction of a HP loss keep the original 530 chain. I can detect a very slight increase in friction when I spin the rear tyre on my bikes when they are on the centre stand. All my street Nortons wear 520 'O' ring chains. My race Norton wears a 520 standard non 'O' ring chain.

Gary Slabaugh (gdslabaugh@sprintmail.com) on NOC-L 3rd. Feb 1999

 

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