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5 Speed Gearbox

Mickthevin

Well Known and Active Website User
Non-VOC Member
WE HAVE A HOTEL UP HERE IN WHITLEY BAY - THIS WEEKEND AND LAST WEEKEND WE HAVE HAD TWO BIG HARLEY CLUBS ; ONE FROM LONDON AND ONE FROM MANCHESTER. PART OF MY ONEROUS DUTIES AS MEIN HOST IS TO TAKE THE LADS AND LASSES ON A RIDE OUT OR TWO OVER THE WEEKEND
I HAVE BEEN LEADING BOTH GROUPS ON MY COMET WITH AN AVERAGE OF 300 MILES EACH WEEKEND. I WON'T TALK ABOUT SOME HARLEY RIDERS ON
1600cc MACHINE THAT CAN'T KEEP UP WITH A 55YR. OLD BIKE WITHME AND MY WIFE ON - AND I'M NOT THE LIGHTEST PERSON IN THE WORLD.

THE BIKE WAS JUST STUNNING - THE ENGINE IS A BORED AND STROKED BOB DUNN SPECIAL. THE ONLY ISSUE I HAD WAS ONCE WE GOT UP TO 70/75 I WAS LOOKING FOR ANOTHER GEAR
DOES ANYBODY KNOW OF A GEARBOX THAT WOULD GO ON AN OTHERWISE STANDARD COMET WITHOUT ANY MAJOR ENGINEERING ISSUES.
ALSO IS THERE WRITTEN ANYWHERE AN IDIOTS GUIDE TO SETTING UP THE FRONT BRAKE

LOOK FORWARD TO HEARING

MICK
 

captain vincent

Website User
Non-VOC Member
Mick,

Give me aring on 01506 416774,and I will tell you a very simple method for setting up the front brake that works with no tecno vinny bull****e.

Captain Vincent (ex North East,banished ti Scotland for 15yrs!)
 

dave g6xnc

Well Known and Active Website User
Non-VOC Member
Kapitain

Glad to hear that the comet (best bike vincentents made) is going strong and that it showed the posers the way home!. Front brakes, this is poorly described in nrichardsons bible, but the way is; Lie on the ground in front of the bike(if you havent a lift) and look at the cam arms on (the brake operating arms) get someone to apply the front brake. Now, you are looking at the brakes in the applied position and the arms must be paralell looking at them from the front. Now look at the arms from the side the angle should still be less than 90 degrees, if not, the arms must be slackend off and adjusted
unit till THEY ARE PARALELL IN THE APPLIED POSITION. Dosent matter if their out of line in the "off" position but they MUST be paralelell when applied. If you cannot get them to align correctley remove the arms and also the serrated disc that the arm bolts against turn this 90 degrees and try again.
This is abit fiddly but belive me you will notice the difference if you've done it
correctly, I only figured it out after quite a lot of experinting and have always reckond this to be a good way of determining someones knowledge of vincents. If the lever comes back to the bars or twin pulls are installed they've missed the boat, so, try it and be carefull when testing, 'cos vincent brakes DO WORK. ( better than BMW's). Gear box, have you tried altering the overaul gearing?, I fitted an amc norton box to my comet for racing
This is not a five minute jod an e ntails machining away the inner chain case behind the clutch (to take an amc unit) all very good as you could then possibly get a Rod quafe five peed conversion for it. I appreciate this is the ravings of an old fart regarding gear boxes but this would seem to be the right direction as moxt (all?) Jap gear boxs are unit contruction with common
oil supply (no chopping jobs) The brake adjusting will work but you must take tyour time , remember Vincents are engineers machines. ( thats why I love my BMW tractor (1150GS) it aint!), lights are crap so are the brakes!.
Good luck withit.
dave gs.
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Five speed box for Comet

I have a five-speed cluster which I used in my Manx that I no longer need (having replaced it with a six-speed). It will fit straight in to an AMC casing - which is what it came out of! I also have the correct Newby clutch centre for it. If you are interested, contact me directly via
sunbeam42@tiscali.co.uk or 07767 328 615.
(I've inserted what amounts to "an ad" here since it is relevant to the thread, rather than in flogger's corner.)
 

Piston Pete

Well Known and Active Website User
VOC Member
Hmm.I too would like some "guidance" on the front brake set up routine. My comet's brake lever comes back to the bar ,but the brakes seem to work well enough,although the "feel" would lead you to think that the lever isnt actually connected to anything.

Re the lads on the Harleys and keeping up, I am just back from a 2200mile tour of Spain and my companions on a sports bike,big traillie and mega scooter found the twisty mountain roads a bit difficult to handle (i.e. keep up with me),but on the motorways they were happy to blast past with gay abandon.

Peter Redmond

Dublin
 

Black Flash

Well Known and Active Website User
VOC Member
Hello Mick, I have just received my engine back from Bob Dunn. It had the same treament as yours, bored stroked, 36 mm carb, MKII cam and so on. When I spoke to him about the gearing, he told me that I have to increase the size of the g/box sprocket by 3 teeth for a start or maybe 4. He told me that the engine has so much torque that increasing the overall gearing by 20% will have no effect on acceleration as the engine doesn't built up speed fast anyway due to the long stroke of 100 mm. His words really make sense to me and with a gearing about 20-25% higher you should get enough terminal speed without the need of a 5 speeder. You should also keep in mind that the engine should rev a bit when cruising to dampen the power pulses of this big bang engine in the poor old Burman gearbox. I am just building another Comet special with a Terry Prince 600 cc topend and use an AMC commando gearbox with special machined lugs, possibly the strongest of all the english gearboxes. If you fit one of these Commando boxes, there is no need to machine the primary chaincase as the mainshaft is longer than on the earlier AMC boxes(ie. Atlas). as much as I know there are drawings for Converta engine plates in 40 years on or some other publication, I am sure they were in MPH yaers ago, but you can certainly ask Ben Fietje, cause he is using this conversion on his racing Comet.
Hope I could help you a bit
Bernd Schmitz "Black Flash"
 

BlackLightning998

Well Known and Active Website User
VOC Member
Hello Mick, I have just received my engine back from Bob Dunn. It had the same treament as yours, bored stroked, 36 mm carb, MKII cam and so on. When I spoke to him about the gearing, he told me that I have to increase the size of the g/box sprocket by 3 teeth for a start or maybe 4. He told me that the engine has so much torque that increasing the overall gearing by 20% will have no effect on acceleration as the engine doesn't built up speed fast anyway due to the long stroke of 100 mm. His words really make sense to me and with a gearing about 20-25% higher you should get enough terminal speed without the need of a 5 speeder. You should also keep in mind that the engine should rev a bit when cruising to dampen the power pulses of this big bang engine in the poor old Burman gearbox. I am just building another Comet special with a Terry Prince 600 cc topend and use an AMC commando gearbox with special machined lugs, possibly the strongest of all the english gearboxes. If you fit one of these Commando boxes, there is no need to machine the primary chaincase as the mainshaft is longer than on the earlier AMC boxes(ie. Atlas). as much as I know there are drawings for Converta engine plates in 40 years on or some other publication, I am sure they were in MPH yaers ago, but you can certainly ask Ben Fietje, cause he is using this conversion on his racing Comet.
Hope I could help you a bit
Bernd Schmitz "Black Flash"
Hi, I'd love some more detail on how to tune the brakes on the front as well - soounds like there are a few of us that would like to benefit from the advice of more experienced owners - mine work fine, impressed the MOT chap - but the lever comes back to the bars.

I'll watch the thread with interest - perhaps we should start a new one on front brakes?
 

Tom Gaynor

Well Known and Active Website User
VOC Member
Altered gearing

That's a HUGE increase in gearing. I race the Manx with 19 and 20 tooth gearbox sprockets (Newby belt drive). 19 is for Cadwell and East Fortune, 20 is for Chimay and the Ulster (both with long 130 mph+ sections). Of course you must try it out first, but the problem with a four-speed box is that, say you were getting 25, 50, 75 and 100 at peak revs, with higher gearing there is an even BIGGER gap between ratios, so to "knock it back one" without locking the back wheel and knotting the valves, you would have to drop the speed from (say) 120 to 90. Generally the concensus on five and particularly six-speed boxes is that "they have a gear for every corner", and while no doubt Lea Gourlay would perform well with a three speed box in a manx, five and six-speed clusters have virtually taken over.
The only circuit I can think of that a four speed works well on is Knockhill (there are doubtless others) where series of corners can be taken at similar speed in the same gear, and going up and down the box is largely confined to straight line stuff.
As you can probably discern, I'm a complete convert. Everything about it is better: the ratios, the closeness of the ratios, the ease of changing - and the reliability thus far, fingers crossed........
 

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