• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

600cc Comet Carbie?


Glenliman

Well Known and Active Website User
VOC Member
Just read an old MPH interview of PCV on the big port heads, which PCV said they first made in 1950.
Same as in nineteen sixties and seventies hotrodding , both ports and valves were enlarged for power.
We now know that making the exhaust port too big kills power. Making the inlet valve and port can definitely add power, as long as the shape is right.
Finding that shape is the tricky part.

Terry's current heads use standard sized Vincent exhaust valves and a smaller than stock exhaust port with the floor filled in to create the sideways D.
Inlet ports are greatly enlarged (38 mm vs 28)
Inlet valves are stock Vincent size but get lifted pretty high by some of his cams. Stock Vincent valves are big valves, I guess intended to work well with low lift MK1 cams.

Add to this the TP squish band mentioned by TT and combustion chamber shape differences. Looking at all of that, while both types are big port, there are more differences than similarities.
Did the factory use two plug ignition on their big port heads?
I couldn't find reference to this in the PCV interview.
He did mention that the oversized exhaust valves caused problems for them by breaking.

Glen
 

vibrac

Well Known and Active Website User
VOC Member
It does look the same as the one Vincent Spares help develop but If it is and if that is a copper pipe the picture is to dark to see how close to the live terminal of the starter lead it gets.
As to ignition and how far advanced to the 'cliff edge' you go, while racing you can be fairly certain of what you put in the tank. But you cant trust the UK petrol outlets the authorities seem more interested in the contents of washing up powder than the octaine rating of fuel
 

Dave Hulstone

Website User
VOC Member
Hi Ian, I have only had it fitted for a couple of weeks now so it's a bit early to tell yet. Yes it is the same as the one VOC are stocking and I believe there are 2 others fitted out there. The cost initially was a bit hard to swallow $3800 Aus. but as the Australian stockist lives around the corner from me and was keen to use me as a Guinea pig, fitting was free, which helped a lot.
My bike has a TPV 600 kit fitted so I did wonder if it might be out of Altons design parameters but it does start very easily, even when not pulling the decompressor when the engine is warm, something that the installer advised. My bike was previously a prick to start. I have a Dellorto fitted and I found if I flooded it I could forget it for half an hour. Soooooo many hot days were spent fully clad kicking and kicking........... Those days are over and what a relief.
 

b'knighted

Well Known and Active Website User
VOC Member
Thanks Dave,

My Bob Dunn 636cc seems too much for the Bob Dunn starter. On the days that it worked it was OK but if it didn’t start instantly there was always going to be pain. Running out of fuel was also a pain as the reserve didn’t have sufficient pressure to force fuel past the designed in airlock on the top feed Mikuni carb. Always running with a full tank only works if you live in a city. Re-designs in progress.
 

b'knighted

Well Known and Active Website User
VOC Member
That’s my calculation of 90 bore x 100 stroke, possibly done mentally while thrashing up a long dual carriageway.
I bought it the biggest Odyssey battery that would fit with alongside the Thornton coil over but still had problems.
 

vibrac

Well Known and Active Website User
VOC Member
Go for lithmium
That Comet Electric start video - check out the battery , inside a Exide case!
CCA wont be a drawback (but the cost might)
 

MartynG

Well Known and Active Website User
VOC Member
Go for lithmium
That Comet Electric start video - check out the battery , inside a Exide case!
CCA wont be a drawback (but the cost might)
If you can afford the starter the cost of the battery should not be a problem
 

Dave Hulstone

Website User
VOC Member
I went for a Lithium. It’s huge and won’t fit in my Exide box. It was about $240 from memory and has a digital display telling you its state of charge. I’ve never seen it below 13.3V even when I’ve started the bike 10 times without riding it (charging it).
I’ve pulled all the stickers off it so it’s just Matt black.
 

Latest Forum Threads

Can't Find What You Need?

Buyer Beware: Fake or Real?

Top