Gear Ratios. Which gears are fitted?

[Seán Ó Maoildeirg]

I feel that my first gear ratio is a little high because I need too much throttle and clutch slip to get away. I bought the '50 Rapide in last November from Christian Patzke in Hamburg. When I recently attempted to email Mr Patzke I learned that he has recently died (26/06/2013). Some loose gears were included in the spare parts.

Other than taking the cluster out and measuring, is their a way I can determine the ratios fitted for 1st, 2nd, 3rd and 4th. Rear wheel is 19" and the larger 48T sprocket is in use. It also carries a 46T sprocket on the left side. I have tried to measure the gearbox sprocket but find it too difficult.

 

[davidd]

Sean,

Yes there is, but I have never done it. First, I would consider simply changing the rear sprocket to 50T. The 46T you have on there is too tall to do you much good. You may have to use a longer chain as a result of going to 50T, but for street riding it may be just what you want. It is very likely that if it feels way to tall for you that you do in fact have the Intermediate gears.

To get back to the gears you can look at MO12 in the spares manual. What you would like is the MK2 gears which shows a ratio of 1:2.60. This means, if I am correct, that for every 2.6 revolutions of the engine the counter shaft sprocket rotates once. Thus, in fourth gear, which is 1:1, the engine rotates once and the CS sprocket rotates once, giving the highest speed.

The Intermediate cluster is 1:2.07. So, the engine is moving only 2.07 revolutions per CS sprocket revolution. If you take out the plugs and move the the rear wheel you could mark the CS sprocket and see if it turns twice or two and a half times. Alternatively, you might try counting links from a particular reference point. The CS sprocket is most likely 21 teeth as that is the stock item. You could count the links that go by in two engine revolutions in first gear starting at TDC and it will probably be 43, which is the Intermediate ratio.

Good luck!

David

 

[timetraveller]

You have to take into account the reduction in the primary drive, between the engine sprocket and the clutch sprocket, as well if counting engine rotations and rear wheel rotations

 

[vibrac]

You may have a high bottom gear a rare bird nowadays a racing extra I believe
normally 998 standard first gear was always a pain I felt because designed for a sidecar tug it always felt to LOW for me that was the best bit about fitting a 5 speed box I got a perfect proportioned 1st gear ratio.
and thats the important bit its proportion to second not necessarily road speed

 

[Howard]

Put the bike on the back stand, remove plugs and clutch cover, put bike in top. Put a marker by the rear chain, turn the clutch one full turn and measure how far the chain's travelled (counting the number of links travelled will tell you how many teeth on the gearbox sprocket). Repeat for third, second and first gear. Divide top gear distance by third gear distance to give third ratio - top by second, top by first - should be accurate enough to tell if you've got high bottom ratio fitted.

H

 

[timetraveller]

Just to make sure that all readers are familiar with this; the early Black Shadows had a gearbox internal ratio of 2.07:1 giving an engine to wheel ratio of 7.25:1. This allowed up to 70 mph in first gear causing consternation and high laundry bills among most other vehicles of the time. This ratio was found to be too high in slow moving traffic and after engine number 7076 all Shadows had the same first gear ratio as Rapides, 9.1:1 overall. There was also reputed to be a close ratio box available for racing (Lightnings) but many people believe that these never existed. However, among my bits and pieces, buried under the debris of years I believe that I do have such a gear cluster which would give an overall first gear ratio of 6.77:1. Any high first gear that one is likely to come across by chance nowadays is likely to be an early Shadow one.

 

[roy the mechanic]

Sean, is this your first Vincent? Remember you are riding the fastest production motor cycle the world has seen up until about 1970? I would reccomend- ride it some more, get to know it a bit better, Im sure it will become your "best freind" , as my rap has become to me. If it aint broke, or misbehaving, do not fix it or otherwise give it a hard time. Go out and enjoy it for what it is- THE BEST MOTORBIKE IN THE WHOLE WORLD ! Regards, Roy.

 

[Seán Ó Maoildeirg]

"

If it aint broke, or misbehaving, do not fix it or otherwise give it a hard time. Go out and enjoy it for what it is- "

The problem with the gearing only arises when moving off from a stand still. It is downright embarrassing when I need to do a hill start with excessive clutch slip and about 2,800 revs. In heavy traffic conditions, with all the stop-starts it just takes all the fun out of a ride out. Also I'm shortening my clutch's life.

To answer your question -- Yes it is my first Vincent but I'm not new to powerful machines.

 

[greg brillus]

It's beginning to sound like it's got the early Shadow 1st gear ratio plus most likely a 22 tooth front gearbox sprocket as well. Easiest to change the gearbox sprocket back to the standard 21 tooth, or else bite the bullet and change the 1st gear set in the gearbox......Oh well nothings ever that easy.....but it isn't too hard to fix. Cheers....Greg.

 

[Howard]

I didn't know you'd got a rev counter - Easy way, you could check engine revs in first and fourth gear at (say) 40 mph, and divide first gear rpm by fourth gear rpm to get first gear gearbox ratio ........... or just tell us what it's revving at 40 in first, and someone here will work it out.

H