PD: Primary Drive Rapide Chain Problem

[Michael Vane-Hunt]

I think we should resurrect PEI and have him flogged!

What else should we do, make the crank differently, there is a lot of talk about that, do a better job with the cylinders and liners, and of course tapered rollers in the head stock, and those hemi heads are a disgrace, not to mention all that funky stuff going on under the timing cover, and surely they could have found better suppliers for generators, lighting and sparking equipment, and why those tall skinny tires, well except on the D's and touring models, and that horrible seat mounting affair, and I forgot to mention the nasty and very problematic clutch. If he was such a future thinker why has it taken us close on to 80 year to now start finding "proper" solution to this horrible piece of machinery. I've only managed something like 150,000 miles on them with only one breakdown that required retrieval, and even that was self inflicted. Should have pulled the crank apart after a major bearing failure and I would have found the hard bit plugging the oil hole in the crank pin, even then it took around 10K miles to rear its ugly head.

No, I have an RC51 that has all the trick stuff, but never my first choice to go out and live life with.

You forgot the pathetically small petrol tank.

 

[oexing]

Allright, so its great to keep things as they are. After all, it is a national monument, so unacceptable from anybody non-British to post ideas for improvements. Seems some are quite pleased to accept as is, some do mods in all sorts of ways as they like. Sorry for those who had to weld their engine cases, must be hundreds of them, I got one too. Sorry for those, who found broken ESA springs - plus that sort of mess like here, possibly just because of these springs - with costs of close to 1000 Pounds maybe. My guess, the Phils got some idea that the first design of ESA was not quite up to the job, did a D type after that - with not quite 100 percent success. And so on, who am I to tell, there are lots of postings here and in MHP about all sorts of "imperfections" , Norman or Greg some of them who can add more to this with more competence than me, non-British too. No, no respect for anything poorly designed, be it Vincent, BMW, Horex or anything, you can find anything anywhere which is crap - and I say so . . . .

Vic

 

[bmetcalf]

Vic, your writeups are very informative and interesting and it would be great to try your ideas. My barrier is no machine shop and no talent or experience to match. I am able to enjoy my bike with it pretty standard, especially me at 73 years old. I was lucky to get it in pretty good condition in 1980, for a reasonable price, and could never afford another after that.

 

[greg brillus]

My guess is it was all about "time" or not enough of it to make things better........To come up with a post war machine ready to hit the market as quickly as possible........Sure there are plenty of defects with these bikes........from someone who has spent my life mostly as a mechanic, a lot of these issues are from poor maintenance and from some folk who seem to be able to destroy anything no matter what it is. Some of these bikes/engines have had terrible lives, and some very easy lives........Not forgetting that the supply of factory parts dried up, so by the late 60's it would have been very difficult to keep one of these bikes in top running condition unless you had some machining ability or similar. A lot of the bikes you see back on the roads now have been built up from parts where the engines were used and abused for racing, due simply to the large capacity of the engine for that era.........when these engines are pushed hard, they can and will fail. A major design flaw with the new fork design these days would probably have quickly seen the company fold from major lawsuits, especially after several folk might have lost their lives due to the bad handling issue........But there are few if any classic bikes that have a look that any motoring enthusiast can see as pure "Art" without even turning a wheel....... A lot of early motorcycle engines are simply beautiful to look at, the Vincent twin is probably at the very top of this list.........The 2 cylinders looking something like a pair off a radial aircraft engine, the short angular pushrod tubes, the exhausts exiting from the front of each head........Either polished alloy or in gloss black.........their performance and enjoyment to ride.......not something every man will ever get to try.......So for all their faults and issues, most all we have been able to sort out and improve upon if we wish to over the years.......Sometimes we need to remind ourselves how lucky we are to be able to have and enjoy these machines......... well better that something of equal beauty just "Hanging on the wall"........

 

[Peter Holmes]

I note nobody has mentioned the shock absorber on the Comet electric start

In fact Vic does mention the Alton electric start shock absorber on page 3

 

[oexing]

The Alton shock absorber on the crank is basically a plate with holes in it and filled with fat o-rings. These act on pressed in pins in the corresponding plate. Allright, better than nothing, at least no bashing loads from this like with the standard ESA. But for having some more degrees of cushioning the rubber needs ample space for deformation else you get only minimal absorption. Just this idea could be copied for a dynamo drive flange for protection of rollers and sprocket. Not a big deal for machining that.
Again, just recently in this posting I came to suspect another root of the drama, but nobody had info about this still : When detecting split rollers in the drive side, do they come with broken ESA springs each time ? Or have some had split rollers with all ESA springs in their place ? Whenever I come upon troubles I am interested to learn and find out what the root of the defects may be. An active forum seem to me a great place for discussions and in time from all aspects we may get a reasonable idea how to care about such things for prevention.
Anyway, it seems not unlikely that broken springs might find their way around the clutch sprocket to jam the dynamo sprocket with damage on rollers and sprocket teeth in consequence. So when that is found more often, the drama like here stems from broken ESA springs and less so from the harsh primary chain drive with its poor ESA behaviours. A cushioned dynamo sprocket would not be helpful if that were so and we´dbe barking up the wrong tree ??

Vic
Found the Alton photo, but they should have fitted real o-rings, not lengths of hose. The rubber needs space for compression or no damping at all. Also I see no bearing bush for the sprocket on the flange, the rubber wiill not take side loads from chain pull .

 

[greg brillus]

I pulled one apart on a friends 600 Comet a bit over a year ago, and those yellow donuts had basically near destroyed themselves, the pins had pushed near right through to the drive side and some of the yellow material was starting to bulge out the sides.

 

[Bill Thomas]

Apart from badly made chains, Most broken rollers over the years have been because the dynamo is too much in mesh,
We have all heard the whine at Vincent meetings as the owners have rode away.

 

[Marcus Bowden]

After my 1990 rebuild in France I had a whine in the primary and was trying to turn my ET 202 round a bit more to disengage the dynamo more but only got rid of it when `I renewed my clutch sprocket as it wears much faster than the engine sprocket which has now done over 500k and have my third clutch sprocket.

 

[Bill Thomas]

While we are talking about this,
We have been told there is a shim to put under the fitting the dynamo sits on ?,
To take the sprocket further away if needed ?,
I have never needed or seen one , But good to know ?.
Also important to have the sprocket central in the chain,
Worth taking your time to get right ?.