Primary Chain Replacement

Hello all,

I opened up the primary case on my 1971 Roadster, to examine and clean the clutch plates in response to a slipping clutch. Good timing, as the (Renold, possibly original) primary chain has lost about a dozen of its rollers, the fragments quietly piling up in the bottom of the case. So, while there are still hundreds of rollers in service, it may be wise to replace it.

It seems the readily available choices are Renold (British), Regina (Italian?) and KCM (Japanese). Does anyone have informed opinion on the relative quality of these?

I'm not interested in a belt conversion. I understand people have had good results with duplex Iwis chains, but I don't think they're available in the US - and international shipping these days is unreliable.

Thanks,
Dave

Jason the chain man is the best, the rest is crap most replacement chains are not the same quality as the original chain and don't use it till you replace it, clean your clutch plates and fill with ATF F and don't overfill only 7 floz at the most, the chain man is great to deal with and quick delivery and good prices.

Ashley

Ashley,

Thanks - good advice - but I think Jason is in the UK, and overseas shipping is disrupted due to the virus. I'm looking for a supplier in the US, as I don't want the bike down for a long period.

Dave

DavidH said:

Ashley,

Thanks - good advice - but I think Jason is in the UK, and overseas shipping is disrupted due to the virus. I'm looking for a supplier in the US, as I don't want the bike down for a long period.

Dave

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could you find out what Jason supplies and source it elsewhere, or check actual postage times, may not be how you suspect?

You will find it will be shipped and delived very quickly.

Ashley

There’s an Iwis duplex chain fitted to a Mercedes that always used to be recommended. It’s worth searching the forum for the model and trying your local Mercedes dealer.

D67HP is the cam chain for a Mercedes Diesel. Worth a try. That was recommended by Andy before he retired.

peter12 said:

D67HP is the cam chain for a Mercedes Diesel. Worth a try. That was recommended by Andy before he retired.

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That is the Merc big pin chain, duplex form its perfect for the primary and in the same form it works on the much higher horsepower Laverda primary, and in simplex form also is the best performing Norton timing chain. It works by using the best materials plus the biggest bush size within the size parameters so each bush wears less.

Jason is Andy's son and has taken over the company.

DavidH said:

I opened up the primary case on my 1971 Roadster, to examine and clean the clutch plates in response to a slipping clutch. Good timing, as the (Renold, possibly original) primary chain has lost about a dozen of its rollers, the fragments quietly piling up in the bottom of the case. So, while there are still hundreds of rollers in service, it may be wise to replace it.

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I would be absolutely terrified to find that. The triplex chain is quite reliable, they don't lose rollers without reason. WHY did it fail?

maylar said:

I would be absolutely terrified to find that. The triplex chain is quite reliable, they don't lose rollers without reason. WHY did it fail?

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Because the idea of filling a chaincase so low, it gets a tiny splash every now & then is dismal engineering. Chains need oil.

maylar said:

I would be absolutely terrified to find that. The triplex chain is quite reliable, they don't lose rollers without reason. WHY did it fail?

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There was a time when the rollers were split and not solid when proper Reynolds was not available, if it is the split type then they do fall off and if you find such a chain they should be changed immediately. If they are the solid type then yes there is likely something else amiss that a new chain alone will not fix.

concours said:

Because the idea of filling a chaincase so low, it gets a tiny splash every now & then is dismal engineering. Chains need oil.

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Lack of oil would be a valid reason for failure. If the chain is rusty and stretched that would be further evidence.

kommando said:

There was a time when the rollers were split and not solid when proper Reynolds was not available, if it is the split type then they do fall off and if you find such a chain they should be changed immediately. If they are the solid type then yes there is likely something else amiss that a new chain alone will not fix.

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That's good to know. Was '71 in that time frame?

maylar said:

That's good to know. Was '71 in that time frame?

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No not while the factory was open, 80's and 90's when the factory was long gone and the spares supply was limited. The split rollers were formed using a wrapping machine on flat material, as are split bushes, makes efficient use of materials but leaves a weak point as the edges are not mechanically linked. Fine for bushes but not for loaded chains.

DavidH said:

Ashley,

Thanks - good advice - but I think Jason is in the UK, and overseas shipping is disrupted due to the virus. I'm looking for a supplier in the US, as I don't want the bike down for a long period.

Dave

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http://www.oldbritts.com/nor_comm_71_8.html

item 37, p/n 060366

Ella will ship priority mail if you ask, you'll have it in a few days.

I just did a duplex chain from TheChainMan in UK. I requested postal shipment to save brokerage pain from a courier. Took about 7 weeks to arrive. Other items I ordered same day from AN took 4 days but had a extortionate brokerage on top of the heft courier fee, via DHL.

Very happy with the chain. Check your clutch hub for notching. Mine was deeply notched so ordered a CNW hardened one for less than AN oem type. It took 9 weeks to get to me across US border, via post.

Thanks for the thoughts. Here's a photo of the chain, which has solid rollers and "Renold England" stamped on the plates:



Note the four visibly cracked rollers. It's suggested there's a mechanical fault in the area causing the failure - which is plausible, but I can't think of what it would be.

- There's always been oil in the case (and even if not, would it cause cracked rollers?)
- Play is 3/8 - 1/2 inch as specified
- Teeth look undamaged on the sprockets

Perhaps it's just sub-par metallurgy in the original manufacture, with repeated impacts on the rollers causing the cracks.

On a replacement, I'm thinking any of the three readily available triplex chains would work well. It's hard to choose given no technical data to work with. But any decent triplex chain should be able to handle the c. 50 hp of a Commando, and it runs in a clean oil bath - a pretty undemanding application. There don't seem to be a lot of failures in this area, present situation excepted.

The Mercedes duplex timing chain is available from US suppliers, but it uses a master link - anyone have experience with such a setup? I'm not sure if the version Jason in the UK sells also has a master link.

Dave

Concerning MK3 chains...I recently changed a primary chain in a MK3..it is tempting to let them go for a long time because they are self adjusting. This one was actually scraping the bottom of the chaincase and leaving deep grooves. That is bad enough but the real danger is the sliding adjuster pieces were almost at the end of travel and were both very damaged. The foot was wobbling on the shaft. If that were to come loose it would be disastrous.
So..anyone with a MK3 please pay close attention to this. Replace the chain long before it reaches this stage.

No, ChainMan IWIS duplex chains do not have a master link.

If you search for Duplex chain on this forum there are older threads on the topic and why the current triplex makes are poor quality. ChainMan also sells the best built drive and timing chains. Good idea to order all three for a bike to use in future renewals.