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Rapide cams #775924 06/08/19 2:14 pm
Joined: May 2009
Posts: 310
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Paul Sammut Offline OP
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I have a 1951 C Rapide and would like to time the valves with a degree wheel. I can only assume the bike has the original cam lobes but have not pulled them yet. I have read about the Mk 1, 2 and 3 cams and would like to know how I can tell which ones I might have, as the timing appears to vary with each. Are they stamped? Alternatively, are the cam measurements published somewhere which will allow me to identify mine, please?
TIA,
Paul.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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Re: Rapide cams [Re: Paul Sammut] #776357 06/13/19 11:12 pm
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David Dunfey Offline
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Paul,

I have all that data if you wish to contact me directly.

The Mk1 cams are a fairly low lift cam (.330" or so). They have good torque and start easily.

The Mk2 cams are a race cam that many owners use. It requires several internal mods to make clearance for the extra lift (about .365"). The do not start as easily as the Mk1's.

The Mk3 cams are simply the Mk1 with some quieting ramps. I would treat it like the Mk1 because it is hard to find the quieting ramps and the Vincent is not a super quiet engine anyway. The two cams, Mk1 and Mk3, should be interchangeable.

The number is sometimes stamped into the groove on the cam when you look at it from the gear side. That groove is there to guide the cam into the gear with the correct positioning while you are pressing the shaft into the gear. Most owners do not separate the shaft from the gear.

If you buy cams from Megacycle ask them not to insert the phosphor bronze bushings. These have a propensity to seize and they can cause lots of expensive damage. Megacycle believes that these bushing were used originally by Vincent and they were. However, they had a small number of cams seize on the spindles. Ted Davis, a developmental engineer at Vincent, found that when they changed to Oilite bushings they never had a subsequent seizure. Oilite is the only Factory recommended material. Phosphor bronze will usually seize. I had a Megacycle cam seize after 3 years of use in an engine so it can be an ongoing problem. I only use Megacylce cams, so I love their cams and throw away the bushings.

David

Re: Rapide cams [Re: David Dunfey] #777588 06/30/19 4:18 am
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Paul Sammut Offline OP
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David,
Thank you so much for your kind reply. I haven’t been on this site for a couple of weeks as work has kept me too busy to mess with bikes. That information is very helpful, indeed. I believe I have the Mk 1 cams and will heed your advice.
All the best,
Paul.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four

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