Terry Prince 600cc conversion

[redbloke1956]

I would like to hear from anyone out there with experience with the 600cc TPV Comet conversion.
Re: How well does the stock clutch and gearbox handle the extra hp, Approx how much increase in hp was gained, Which cam/carb is most suited etc.

Regards
Kevin

 

[Black Flash]

Hello Kevin,
i have the same topend on my black flash (hence my name here). I am using a 36 mm Mikuni VM carb on that engine and have a TP race cam in it. well the one he made 10 years ago. I somewhere have a diagram of the cam.
I had to experiment with the exhaust a lot cause it the exhaust noise which stopped me from getting the bike road registered. It was first fitted with an Armours Goldstar silencer > 121 db. the MOT guy is doing classic racing on a G50 but when he heard the Comet he went pale in his face.
then i tried all sorts of silencers i could get hold of for trial runs in the fields. I finally found a noname readily available one from a dealer on the internet for 50 GBP. which sounded and felt ok.
It also changed the engine characteristics and made it much more pleasing. Before the engine a was real Gold Star RTT2 sort of . madly slipping the clutch , if the revs dropped the engine would die, now it is almost like a standard cam, but with MUCH more grunt than standard Comet.
I went for a Norton Commando N type gearbox, a NA will do as well, just needs a bit more of filing to reduce the width of the g/b lugs.
the clutch I am using is a Commando one with newer friction discs run dry (I am on a belt). due to the horrible engine characteristics at the beginning of my trial period a managed to blue the steel discs just from take offs.

I am still fiddling with the bike now and I won't take it on a dyno before it has done at least 2000 mls, so I can only guess.
but from the way the bike accelerates I am sure it must be over 40, more like 45 bhp. But that is just guesswork.
Hopefully a dynorun will tell that year. But just standing next to the bike and listening to the tick over, which goes bang, bang, bang…. compared to a more likely puff, puff, puff on a standard Comettells you all the difference and dare I say it..give you goosepimbles.
Oh I am also using twinspark ignition.

cheers
bernd

 

[greg brillus]

Kevin, I remember something about an increase in power from the original 28 HP to about 35 HP with most other stock items on the engine. However if you changed carb's, cam and so on I think a higher output would be quite achievable. Obviously the change in capacity is a 20% jump anyway, and the newer type squish band combustion chamber will allow quite high compression ratio's without the detonation you would suffer doing same to original hemi chamber heads. It is definitely worth doing if not expensive, but most folk I know who have done it swear by it. Cheers......Greg.

 

[Monkeypants]

What are the vibration levels like with increased capacity and higher comp., both of which tend to add to vibes?
Glen

 

[redbloke1956]

Hello Kevin,
i have the same topend on my black flash (hence my name here). I am using a 36 mm Mikuni VM carb on that engine and have a TP race cam in it. well the one he made 10 years ago. I somewhere have a diagram of the cam.
I had to experiment with the exhaust a lot cause it the exhaust noise which stopped me from getting the bike road registered. It was first fitted with an Armours Goldstar silencer > 121 db. the MOT guy is doing classic racing on a G50 but when he heard the Comet he went pale in his face.
then i tried all sorts of silencers i could get hold of for trial runs in the fields. I finally found a noname readily available one from a dealer on the internet for 50 GBP. which sounded and felt ok.
It also changed the engine characteristics and made it much more pleasing. Before the engine a was real Gold Star RTT2 sort of . madly slipping the clutch , if the revs dropped the engine would die, now it is almost like a standard cam, but with MUCH more grunt than standard Comet.
I went for a Norton Commando N type gearbox, a NA will do as well, just needs a bit more of filing to reduce the width of the g/b lugs.
the clutch I am using is a Commando one with newer friction discs run dry (I am on a belt). due to the horrible engine characteristics at the beginning of my trial period a managed to blue the steel discs just from take offs.

I am still fiddling with the bike now and I won't take it on a dyno before it has done at least 2000 mls, so I can only guess.
but from the way the bike accelerates I am sure it must be over 40, more like 45 bhp. But that is just guesswork.
Hopefully a dynorun will tell that year. But just standing next to the bike and listening to the tick over, which goes bang, bang, bang…. compared to a more likely puff, puff, puff on a standard Comettells you all the difference and dare I say it..give you goosepimbles.
Oh I am also using twinspark ignition.

cheers
bernd

Thanks Bernd, I will be very interested to hear of your Dyno run, how much was the Norton Gearbox?

Thanks again mate.
Kevin

 

[davidd]

I think the 28 bhp. is at the crank, but I would not be surprised if the Prince top end was giving 35 at the wheel. I think it is difficult to get over 35 with any silencer, even a straight through. When I put a racing straight through silencer on it cost 5 bhp. on the dyno. The entire exhaust tract of a Vincent is pretty tricky to tune.

I have heard that Terry's kit provides gobs of torque, which makes a Comet an impressive ride on the street.

David

 

[vibrac]

So are we talking about Kit that is still on the market? can we still buy TP top ends etc ?
As for silencers a good 4" diameter straight through absorbtion silencer keeeps it below 105db unfortunatly that means high level exhaust. The things we have to do to keep the sport alive, I dont suppose anyone ever got a football crowd to keep quiet

 

[davidd]

So are we talking about Kit that is still on the market? can we still buy TP top ends etc ?
As for silencers a good 4" diameter straight through absorbtion silencer keeeps it below 105db unfortunatly that means high level exhaust. The things we have to do to keep the sport alive, I dont suppose anyone ever got a football crowd to keep quiet

Tim,

Yes, the photos I took in the thread on this were of parts that had just arrived from Terry.

http://www.vincentownersclub.co.uk/index.php?threads/terry-prince-top-end-kit.6599/

David

 

[Black Flash]

Hi Kevin,

Norton boxes go for all sort of prices today, sometimes you get a nice one for 120 quid sometimes they are nearer 300. Just make sure you get a Commando one type N or NA. I bought a new Commando mainshaft years ago to fit into a Dominator box, but this is a no brainer today as a new mainshaft is about 100 quid or so. I have never tried fitting a standard Commando clutch as well (mine is a belt drive), they sell pretty cheap second hand and have the same pitch triplex chain as a Vincent twin, so easy to fit a twin triplex sprocket to a Comet. But I am not sure about the clutch diameter will go into Comet chain case.
if it did it would be a great combination, good box, good clutch (with surflex plates), strong triplex chain…. what else could you ask for.

Maybe somebody in the club still has an old Commando clutch basket to give us some measurements.

Bernd

 

[highbury731]

Hello Kevin,
i tried all sorts of silencers i could get hold of for trial runs in the fields. I finally found a noname readily available one from a dealer on the internet for 50 GBP. which sounded and felt ok.
It also changed the engine characteristics and made it much more pleasing.
cheers
bernd

Can you tell us how to find the silencer, and does it work with twins?