Sprocket interchangeability

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SeanG
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Sprocket interchangeability

Postby SeanG » Wed May 15, 2019 12:34 am

Hi all,

I am preparing to reassemble the bottom end of my R60/7. Basically, I’m up for ordering a new camshaft, chain, cam sprocket & oil pump rotors.

It seems ‘77 - ‘78 had some transitions, namely duplex to simplex chains. I gather the crankshaft remained the same.

Mine previously had the duplex chain. But I have since removed the mechanical tachometer cable, and I plan on installing a cam-mounted timing advance.

So my question is, would it be possible to use the later style single chain & sprockets? The parts seem to be cheaper, so there is that advantage. But if it were possible, I am guessing it would be the better (newer) system?
My bike is a 1977 R60/7.

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Rob Frankhamr
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Re: Sprocket interchangeability

Postby Rob Frankhamr » Wed May 15, 2019 10:00 am

A simple answer... No.

The camshafts aren't the same and the timing chest covers are quite different. The ignition triggering arrangements are also completely different and dependant on the nose of the camshaft. Even if you replaced the timing chest, and all of the associated parts, you would still have to replace the front main bearing support and I don't think the later support would work with the early crankcase. To put it another way, you'd end up having to replace most of the engine (or carry out major engineering modifications to the parts). Really, you're much better of sticking with the original arrangement...

Rob
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Mike D
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Re: Sprocket interchangeability

Postby Mike D » Wed May 15, 2019 12:38 pm

All what Rob has said, plus the duplex chain lasts a lot longer than the simplex one.

Mike

Neil Robertson
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Re: Sprocket interchangeability

Postby Neil Robertson » Wed May 15, 2019 5:38 pm

Just in case anyone may be interested ,when a catastrophic lubrication failure destroyed the crank and bearings of my R80/7 I bought a slightly later (simplex timing chain and points in bean can ignition)R100RT engine from an autojumble.I swapped the crankshaft (which was identical) along with its bearings and front carrier.
The carrier fitted straight into the crankcase but required some trimming at the front to clear the duplex chain and it's tensioner, the amount of metal that needs removed is quite small and within the capabilitys of a file and dremill.

SeanG
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Re: Sprocket interchangeability

Postby SeanG » Wed May 15, 2019 9:09 pm

Thanks Rob,

I knew there would be a catch. Had to ask though...
My bike is a 1977 R60/7.

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Rob Frankhamr
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Re: Sprocket interchangeability

Postby Rob Frankhamr » Wed May 15, 2019 9:15 pm

Just in case anyone may be interested ,when a catastrophic lubrication failure destroyed the crank and bearings of my R80/7 I bought a slightly later (simplex timing chain and points in bean can ignition)R100RT engine from an autojumble.I swapped the crankshaft (which was identical) along with its bearings and front carrier.
The carrier fitted straight into the crankcase but required some trimming at the front to clear the duplex chain and it's tensioner, the amount of metal that needs removed is quite small and within the capabilitys of a file and dremill.
That's interesting to know... Did the oilways match up?

Rob
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Neil Robertson
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Re: Sprocket interchangeability

Postby Neil Robertson » Wed May 15, 2019 9:59 pm

Yes,I'm glad to say,it was quite a while ago but I remember comparing the two parts and apart from the extra metal both parts were the same.you could actually see where the mould had been altered to make the newer part.


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