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Comet Rear Sets

PaulB

Well Known and Active Forum Website User
VOC Member
Hi,

At 6'2" I feel a little cramped on my Comet, so I was thinking of installing rear set type footrests to give me more room as I never carry a pillion. What do I need in the way of gear shift and rear brake linkages? I know I can use the rear footrests and change the rubbers for kickstart rubbers.

Also, if I was to upgrade it to a 600cc capacity, what is involved? Is it simply a barrel and piston change, or is there more to it?

Thank you.
Paul
 

PaulB

Well Known and Active Forum Website User
VOC Member
Hi Russ,
Thank you for the reply. I have my in-laws with us at the moment, but I will try to call you sometime over the weekend.
Kind regards,
Paul
 

Pete Appleton

VOC Hon. Editor
VOC Member
VOC Forum Website Administrator
600cc

Paul
Increasing to 600cc is not a straight forward swap of parts. I have fitted a big bore kit, supplied by Vinparts, in a special that I am working on. I believe that these comments are common to most of the kits available:-

1. A 90 mm piston is about the largest that can be easily fitted without major work. With a standard crankshaft stroke of 90mm this only gives you 570cc.

2. To fit the barrel in the crankcase, you have to strip the engine and bore out the crankcase mouth.

3. Different weight pistons mean that you should ideally have the crank re-balanced.

4. The cylinder head needs machining to clear the piston and get the right compression ratio.

5. If you really want 600cc then you need to get the crank re-worked to give increased stroke.

I went for 570cc but only because my engine was a wreck and I needed to do all of this work anyway. It is not a job to undertake lightly and is pretty much irreversible.

Peter
 

PaulB

Well Known and Active Forum Website User
VOC Member
Thank you for your detailed explanation Peter. As my engine is fundamentally in sound condition and with matching numbers, I would be reluctant to do anything that would be irreversible. I expect my Comet will be around for longer than me, so I don't really want to spoil the originality for a future owner.
Looks like I'll have to stick with a 500 until I can find that twin with my name on it. :)

Thanks again,
Paul
 

nobby

Well Known and Active Forum Website User
VOC Member
I used another engine for the 600 and kept the original 500 in perfect order. As a spare maybe, but certainly for keeping originality with a complete and matching Comet.
For many years I did not use the foothangers but folding metal footrests positioned more to the rear on Flash plates. The gear lever was just reversed and for the brake I used an old Norton race setup.
Since two years I have a passenger so the need for the foothangers came back. And since recently I acquired those fantastic Mac Read folding foot hangers.
 

Bill Thomas

Well Known and Active Forum Website User
VOC Member
Hello Paul, I am 6' 2" ish and with my Comet I just turned the gear lever round the other way and use the rear footrest moved forward. The brake you will have to weld something up. I hope to do a 560cc job on mine just by stroking it, I have bought a new conrod 1/4" too short, and buy useing a 1/1.4" crankpin ground 1/4" nearer the rim of the flywheels. Money is short so it will have to wait for a bit !! Good Luck Bill.
 
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