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The best set up? Tips on how to rebuild an un-matching Rapide, All input welcome!

Spqreddie

Well Known and Active Forum Website User
VOC Member
Dear All,
This is Eddie (currently living away in a country where there are no Vincent, no special tools nor specialized machine shops..)
I was finally able to acquire a twin which I’ll be starting soon to slowly rebuilt (bike is in Europe, I’m not)
Being away I’m not in hurry, but I’m pushing to have it completed as soon as possible trying not too lose much time.

The machine is a 48 Rapide (acquisition object of a previous post: http://www.vincentownersclub.co.uk/...etermine-authenticity-and-value-of-1017-cases ) which I’m willing to rebuild to be used as much as possible once back in home. As it’s not a matching number, am not looking for a concourse rebuilt but for a reliable enjoyable bike.

I’ve already some ideas but I would like to get your expert advice and i'm sorry if some of the questions have already been treated in previous posts.
First of all, i'will be sending the cases (as were welded around the front primary sprocket) for wrapping check to Maughan.
I’ll also ask them to rebuild and balance the crank for me, and here the first question: piston compression which is the best one for road use and long engine life? 7.3 as per Shadow or 8 as per modern fuel allowance? More than 8 become too extreme?
My idea would be 8:1.

After the bottom end is done, to complete the lower engine part I would need to source a gearbox..again which is the best compromise for fast road use? Rapide or shadow first gear? There is really a difference? I was of couse thinking about shadow specs for the gear box. I’m not interested in a 5 speed type.

As my primary cover is already modified for accepting a multiplate clutch (separate clutch chamber has been cut away) I was thinking to stick with it instead of the original one. Any major inconvenience with that? Is it true that mutliplate clutch allows for quicker gear changing?
And what about the cams and timing chest? MKII or 105?? MKII are to extreme and reduce fuel mileage? 105 still good at all revs? Low torque granted? Top speed ok?
Idler and gears to be lightened with holes??

My idea is for the time being Gary Robinsons 105.. but open to suggestion..
Cylinder heads, I don’t have them, so again I’m pretty free here. I was thinking about Goddens complete heads (front and read, not two front) ported to take shadow specs carb 1 1/8.
For carbs? Again I’m not bind to originality, but just looking for good street performance and reliability so was thinking about a monoblock 389 series as per D shadows. Concentric would be better? Gardner or other are too extreme??
Last thing for this afternoon (more to follow..) magneto: Lucas or electronic BTH?? BTH is for now my choice and was also thinking about an Alton 12v generator.
Thanks to all,
Eddie
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Eddie, What a list !,Having done it WRONG for a life time, This is what I would do, Unless you want to RACE, Keep it soft,7 Pistons, Rapide first gear,Multi' clutch is quicker gear-change, They say the new clutch needs a spot of thin oil. Sorry, never used Gary's 105, But they say they are better than MK11. Carbs, Don't go for Gardner's they are for racing, I have had lots, I would go for monoblock or concentric, Nice and simple. Ask Time-Traveler for one of his Super "Walkernator" . Try E/bay for a D distributor, Oh and don't forget a Hydraulic steering damper !!. Good Luck Bill.
 

b'knighted

Well Known and Active Forum Website User
VOC Member
I started typing out a long spiel saying virtually the same but scrapped it as I felt it was only my opinions. I don’t have your competition experience so couldn’t compare as you can. I entirely agree with concentric carb, belt drive alternator and coil ignition although I would consider the successor to the Lucas Rita –the Moira electronic advance system. I have no experience of it but was impressed by the Rita. I get the impression that the advantages, to a street rider, of a multi-plate clutch is outweighed by it apparent need of frequent fettling /lubrication. The standard clutch is more than adequate, if a little expensive to buy new as a kit of parts.
 

deejay499

Well Known and Active Forum Website User
VOC Member
Similar to some of the other answers. Keep a multiplate clutch, especially as it will run in oil, and transforms the gearbox. Go to standard bottom gear instead of the Shadow high one, much better in traffic. Agree about monoblocs or Concentrics and Walkernator - got them on all my bikes, 360 watts gives loads to spare. A soft enginme has lots going for it, or 8.1 at the most. good luck.
 

Spqreddie

Well Known and Active Forum Website User
VOC Member
Dear all,
Thanks for your tips! And I hope more will come; I am realizing that some of my decision might need to be modified….
Surely regarding the gearbox gearing, I’m now convinced that indeed Rapide ratio might be better,
But for the rest as well I’ll consider your tips, and for the electrics I might think about mounting the D distributor that I’ve inherited with the box of parts I got with the bike.
Thanks…but then more thinking and reading and less sleeping for tonight..
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
hello Eddie, It's like Ian says it's only what I think. I have two twins, One with high first gear and one with low, They are both fine !, But if you live with a lot of traffic, Or carry some one on the back, It will be harder on the clutch. If you want more power go with an 8 and a loud exhaust and i think more vibes', The softer the tune , The longer the bike will last, I am MAD, I have run 12's !! on the road !! What ever you do will be Super, Have fun Bill.
 

Howard

Well Known and Active Forum Website User
VOC Member
I'll go along with all of the above.

I use 9:1 on the road and wouldn't call it "extreme", never used any other CR, so I can't compare.

I changed from coil ignition to Pazon a couple of years ago, and the electronic advance totally changed the engine characteristics (for the better). Coil ignition works well, reliable, and easy to fix, but I really hate centrifugal bob weights (personal choice).

H
 

Rob H

Well Known and Active Forum Website User
VOC Member
I have been studying mods myself, would suggest pazon ignition if you want electronic ignition, the current draw is very low compared with other systems. Would use the rapide first gear, mutch better around town or two up. Unless you have lots of lights would use the latest Alton, believe they have all the issues sorted out now and is a slot in replacement. Not keen on the appearance of the walkernator if it is the one I'm thinking of. Would also fit dave hills centre stand and LED rear/brake light, much much brighter and less current draw
 

Howard

Well Known and Active Forum Website User
VOC Member
I have been studying mods myself, would suggest pazon ignition if you want electronic ignition, the current draw is very low compared with other systems. Would use the rapide first gear, mutch better around town or two up. Unless you have lots of lights would use the latest Alton, believe they have all the issues sorted out now and is a slot in replacement. Not keen on the appearance of the walkernator if it is the one I'm thinking of. Would also fit dave hills centre stand and LED rear/brake light, much much brighter and less current draw

My Pazon draws about 2.5 Amps (12 volt) - The type of coil used will affect the current.

H
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
I am not sure, But I thought you could ride for about 3 to 4 hours on a standard "D", With no charging ? Cheers Bill.
 
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