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Converting a Comet into a Twin.

Mark Fraser

Well Known and Active Website User
Non-VOC Member
With the current price of twins I am seriously contemplating converting my Comet into a Twin.
I am planning on going the route of building a new engine but have discovered so far that their are four people making crankcases? Has anyone recently gone this route? Who's cases are best to use / can anyone recommend somebody that would take this type of job on.

Mark.
 
Hi Mark,
I only know of three. The norvin place, Godet and Molner.
The Godet ones are good and I have been told that the norvin one's are not bad, I am going to get a pair to see what they are like.
Simon Linford will build the engine for you, call me on Monday for more info.
Russ
 

Mark Fraser

Well Known and Active Website User
Non-VOC Member
Hi Mark,
I only know of three. The norvin place, Godet and Molner.
The Godet ones are good and I have been told that the norvin one's are not bad, I am going to get a pair to see what they are like.
Simon Linford will build the engine for you, call me on Monday for more info.
Russ

Hi Russ,
The 4th is DRAT cases from Bob Culver enterprises. He seems to manufacture a load of spares but his work load is quite high at present.
 

manxnortonman

Well Known and Active Website User
VOC Member
Hi Mark,
My engine is built using John Wyatts cases,heads, flywheels and covers.I am very pleased with the result. His number is 07952 866193.

Regards Garry Laurence
 

Mark Fraser

Well Known and Active Website User
Non-VOC Member
Twin engine.

Hi Mark,
My engine is built using John Wyatts cases,heads, flywheels and covers.I am very pleased with the result. His number is 07952 866193.

Regards Garry Laurence

Garry,
Did John build it for you? I'll rob the Comet engine of as many bits as possible and just sell the remaining parts that I don't require. Do you think 11K will get me there with the engine?

Mark
 

Pete Appleton

Well Known and Active Website User
VOC Member
VOC Forum Administrator
11 Grand, You'll be lucky

Do you think 11K will get me there with the engine?
Mark

Mark, I recently built a twin from bits. The Godet cases that I used are excellent, no bits to grind off or holes that don't line up. As for prices ball park figures are :-

Crank cases £2500
2 x Heads with valves etc £2000
Flywheels £1000
Pistons,rods,barrels £1000
Gearbox internals £1000
Primary side internals £1000
Timing side internals £1000
Generator & ignition £750
Covers & cases £750
Kickstart, gearlever & internals £1000
Bolts, studs, fittings, oil pipes £1000

All of these prices are on the low side, many need V.A.T added and you haven't paid anyone to assemble it yet. You will also be amazed at the number of cycle parts that are different.

With a Comet selling for £9000 at Stafford and a Rapide recently selling for £24,000 on e-bay it looks like you could be cheaper to trade up to a genuine twin without butchering a Comet.

I will now stand by for death threats from parts retailers:rolleyes:

Pete
 

BlackLightning998

Well Known and Active Website User
VOC Member
Only a complete XXXXXXXXXXXXXXXXXX would do what what you are comtemplating in my opinion.
Mmmmmmmmm, really helpful opinion - not, but you're free to hold it. Can't work out what's 18 letters long with no spaces though!

It's Mark's bike, he bought it - he can do what he wants with it. Worse has been done before and will be done after I guess.

Oh - and I think it's a real shame too - especially with an all original Conways supplied bike that looks as pretty as his does, but it's his to do with what he wants.

Me, well I reckon in todays world that the maths works out better to sell his super Comet for top dollar and buy a Twin that needs work, and do it over time.

You never know - some member with 10+ Vincents might just offer to swap him a tired twin for his immaculate Comet to save him "doing his worst". Fingers crossed.

Stuart
 

Mark Fraser

Well Known and Active Website User
Non-VOC Member
There's always one.

Only a complete XXXXXXXXXXXXXXXXXX would do what what you are comtemplating in my opinion.

I started the thread as I was looking for advice, Russ, Peter & Stuart have enabled me to make a decision. You give me the impression that your toys were being launched from the pram :D
 

lvhrd

Website User
Non-VOC Member
Not to hijack this thread, but what kind of costs would be involved in building a Comet motor from the cases? Is it even possible to acquire all of the necessary parts?
I ask because I'm thinking that starting with a set of cases (or thereabouts) might be how I get my first Vincent.

thanks,
Chris
 

nkt267

Well Known and Active Website User
VOC Member
but what kind of costs would be involved in building a Comet motor from the cases? Is it even possible to acquire all of the necessary parts?
Start by finding a good set of secondhand cases.Then look for a nice Comet that someone else is selling.It is usually a lot easier and cheaper to 'build' a bike this way. As far as I can tell all other parts are available for a Comet ENGINE.Frame parts may be a different kettle of fish.
http://www.vintech.co.uk/
http://www.vincentspares.co.uk/shop.html
Try pricing the parts from these sites...John
 

MartinRestorer

Website User
VOC Member
Comet to twin

I started the thread as I was looking for advice, Russ, Peter & Stuart have enabled me to make a decision. You give me the impression that your toys were being launched from the pram :D

Mark
I have been trying to acheve what you are contemplating, but taking a comet engine from a Rapide frame and building the twin engine.I have been doing battle with some John Wyatt cases over the last 2-3 years with many obstacles. But I may have been unlucky with this set of cases. But good for a chalenge. O and what was your decision.Good luck Martin
 

Comet

Well Known and Active Website User
VOC Member
Mark , is it just for the power difference that you are looking to convert to a twin? If it is, a cheaper option than the full twin conversion is the 636cc rebore.:D I am not sure of the full details but there was one at the Severn rally. It still looks fairly standard but it puts out power that is comparable with a twin. It would certainly be a LOT cheaper and so much fun pulling up beside a Rapide and leaving them stood at the lights, after all there would still be a big weight advantage.:cool:

cheers

Comet
 

Mark Fraser

Well Known and Active Website User
Non-VOC Member
Mark , is it just for the power difference that you are looking to convert to a twin? If it is, a cheaper option than the full twin conversion is the 636cc rebore.:D I am not sure of the full details but there was one at the Severn rally. It still looks fairly standard but it puts out power that is comparable with a twin. It would certainly be a LOT cheaper and so much fun pulling up beside a Rapide and leaving them stood at the lights, after all there would still be a big weight advantage.:cool:

cheers

Comet

Comet,
I've heard of this recently when I was down the ACE one evening. This chap seemed to think it was Bob Dunn that did this conversion?
Anyone on here had this done to their Comet?
 

Comet Rider

Well Known and Active Website User
VOC Member
Big Bore Comets

Hi Mark,

In regard of big bore/ stroke Comets.
I run one of Vinparts 90mm bore kits, my dad runs a Terry Prince 600cc kit. Both go well with either standard stroke, or Bob Dunn 100mm stoker cranks.

If you want more info, drop me a line..

Neil
 

van Ginneke

Well Known and Active Website User
VOC Member
Hi all, searching the forum for info on 'who makes new twin crankcases' I found this thread.
(Yep, 3 years later.....) I am toying with the same idea to convert (...) a Comet into a Rapide, I have two Comets.
One in process of renovation and another one 'as found' after 35 year in a shed.
So I can butch one....
The best place to get a twin crankcase is Godet?, but I thought he only sells these if he can build a complete one for you, is that so?
Vincent
 

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