Late model Scrambler gauges

[graeme]

Some advice please,
My 450 Scrambler came to me with Veglia gauges that I think came from a parallel twin?
Neither were anywhere near accurate.
I had a pair of Smiths like used on the yellow singles.
The speedo reads slower than the presumed seat of the pants speed.
Question 1, were Smiths gauges fitted to last model Scramblers with 19 inch wheels ?
If yes, would anyone know what the correct wheel hub gear should be ?
Drum is double sided
Rim is 19 inch

Regards
Graeme

[Duccout]

Hi Graeme,

Interesting question, and one that I had not thought of, so I had a quick look at the parts book. The Scrambler Speedo drive ratios are listed as 21/11, but the Desmo and Mark 111 are 22/11, so I am guessing that those models with 19" wheels use 21/11 and those with 18" use 22/11.

Cheers,

Colin.

[Jordan]

I think those ratios could result in reasonably accurate speed readings for both models, using the same speedo gauge.

The SCR overall tyre diameter, based on 3.50x19" is 26", whereas the Mk3 with 3.00x18" is 24".
Circumference equals pi x diameter, so about 81.7" and 75.4" respectively, which is the distance covered with one wheel rotation.

Multiply those circumferences by the ratios 21/11 and 22/11 results in the numbers 156 and 151, approximately. Not too wildly at variance.

[graeme]

Hello Colin and Jordan, thank you both.

I'll get it up on a bench and jack up the front, mark the wheel and the speedo cable and see how many full revolutions the wheel and the cable do relevant to each other.
Then see where I am trying to figure this out. (may have more questions)

I must apologise for all the uninteresting questions lately. It's winter here and I have been sorting out all the "when I get a round tuit" problems.
Best place to be, in the shed with the fire on, music and good red wine, when it's 8 degrees C and raining outside. (nights are between 0 and 2)
(pics if you want)

Regards
graeme

[Duccout]

Hi Graeme,

It is 35 C here and too hot to ride! We can never get it right can we? Pics are always good to see!

Cheers,

Colin

[graeme]

Hello Jordan and Colin,

With the front up off the ground and the speedo cable and front wheel marked with tape,,,
I get 11 full wheel rotations to 21 speedo cable rotations (as close as I can get to full numbers)
Could this speedo gauge be faulty ?

Comments ?

More clues,
When I bought the Scrambler it was a bitza.
18" front wheel with single sided drum.
I had a double sided drum and a 19" Borrani that I laced up with new spokes.
The double sided drum is from an unknown motorcycle, perhaps a Shotgun or yellow drum bike bike with 18" wheel ?
There was a CEV branded cable drive that didn't fit the gearing. (would not spin but seemed to bind up)
Perhaps the "ring gear in the hub is for an 18" wheel ? (is that different to a ring gear for a 19" wheel ?)

graeme

[graeme]

pics,,,

IMG_2516.jpg

...

[Duccout]

Great workshop!