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Comet Top Speed

Russell

Well Known and Active Website User
VOC Member
Will a comet really do a ton?
My comet sits very happily at 50 to 60 mph, I cannot imagine how frightening it would be at 100 mph!
Do they really reach such speed without modification?
 

Bill Thomas

Well Known and Active Website User
VOC Member
With Grey Flash Spec Engine and a 36mm Dellorto, Standard Road Comet, No fairing !.
ONLY ! :D , Got 99.8 at the end of a Flying 1/4 mile, Proper timing at a Sprint Meeting on an airfield,
Nice tail Wind and we had 100 octane petrol back then at the petrol stations, mid 1970s.
No different than 100 mph on a Twin, Which is a piece of cake !.
Would now think would be a good idea to fit an Hydraulic Steering Damper, Only £50 plus brackets.

Maybe Because it was BLUE !.
I am sure it would have done 100 with a smaller rider ?.
 

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b'knighted

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VOC Member
Running a “standard” Comet with chronometric speedo and 20” wheel, my bike would do a registered 85 mph.
it would do this in third gear, pretty well regardless of terrain or load. It would not exceed 85mph in top, being more affected by gradients and headwinds.

Nowadays, 85 in third sounds much too busy.
 
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peter holmes

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VOC Member
I haven't ever bothered to check the gearing on my D Comet replica, but I would guess it has a standard geared Burman gearbox with standard sprockets, but 85mph in third sounds awfully fast to me, I travel to most places with a pillion passenger, which I suppose does blunt the performance a little, well quite a lot in reality. A 20inch front wheel will give you an optimistic reading, 21inch being more likely to give an accurate speedo reading. I run a 19inch front which is probably giving me an even more optimistic reading, but I wouldn't dream of taking it to 85mph in third gear, I would normally engage 4th gear at around 50mph and leisurely make my way up to a cruising speed of 65mph with the occasional foray to exceeding the legal limit. If I do want to go any faster it is so much nicer to give the Rapide a run out.
 

b'knighted

Well Known and Active Website User
VOC Member
That was 40 years ago and I wouldn’t be aiming for that speed now. The point was that the over gearing meant that top gear performance was lower than third gear.
The road tests suggested that the Comet would do 88mph but I couldn’t achieve that.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Trouble is the Bikes are getting Older, like Us !,
I still have a photo of Tony Wheatley's engine in my head, He liked to Buzz it !.

Another day on my Twin, I started on the grass Just before the end of the airfield runway,
To give me even more run in, Trouble was all the riders were in a line across the runway,
With a small gap for me to get through, It was nearly a game of Skittles !!.
 

Bill Thomas

Well Known and Active Website User
VOC Member
Just a few years ago, After fitting a Mk2 Amal carb', It rolled up to 80 mph no trouble on the flat,
I thought it must be a tail wind , So turned around, But it was the same ,
Like me some days it goes better than others :D .
 

Bill Thomas

Well Known and Active Website User
VOC Member
The high numbers as in the photo,
but the 80, Normal bike gear, normal seating but have rear set footrests,
And handle bar screen.
But I was 15 stone and well over 6 foot tall.
Had some health problems this year and lost a stone.
 

Colin

Well Known and Active Website User
VOC Member
My Egli Comet WAS very fast at one time but was detuned on a rebuild. I run a 49 tooth rear sprocket now and comfortable cruising is 60/65 mph .70 mph can be maintained on a motorway but by the time I touch 80mph mechanical sympathy says (shouts!) S L O W E R.
60/65 ish is around 1/2 throttle and the next 1/2 consumes more fuel than the extra few MPH can justify.
Don't bother with the actual top speed just lie through your teeth about it
(I can actually do 120mph easily but then I am a mere slip of a lad, and very aerodynamic, look at the picture, can you doubt it)
 

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davidd

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VOC Member
Will a comet really do a ton?

A stock Comet has about 23-4 BHP at the rear wheel, so 80-85 mph is likely the best it can muster. Most of the Grey Flash racers that are running initially made power at about 26 BHP from the rear wheel. The engines perform much better once they are tuned a little better. David Tompkin's engine started with 37 BHP with a high-compression piston and a Mk2 cam. With a good megaphone and pipe, it got about 2 BPH more. The bike is generally geared to hit 105 mph on the straight because that is doable, but that is using the speed from the corner previous to the straight as a flying start.

The Comet chassis is as good as the twin for high speed. It is not very worrisome at 100 mph unless something is wrong with the chassis set-up.

David
 

Bill Thomas

Well Known and Active Website User
VOC Member
Very good Colin, But that's how some speeds were done in the old days, With a stop watch,
They would have had a job to do 90 with a Standard Comet.
Bit like some of the Jap Speeds, I had a Kwacker 500 Mach3 early one, That was said to do 125,
Not a hope in hell, But very fast for a 500 three two stroke.
The rev's went from 6000 to 9000 like a mad thing, Very dangerous !.
 

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