Timing chain sprockets.

[MIG Wielder]

If you look at the Sprint timing chain sprockets with the timing cover removed, you can see that there are roughly twice the number of teeth on the camshaft sprocket as there is on the crank sprocket. Entirely reasonable as the valve gear runs at half engine speed.
Now looking at the jackshaft sprocket this is a size roughly half way between the crank and camshaft ones.
Intuitively shouldn't that also be the same size as the camshaft sprocket as the distributor also runs at 1/2 engine speed ?
It obviously works in practice.....
Or am I having a(n) (early) senior moment ?
Thanks, Tony.

[yorkshire_spam]

That would depend on the gearing between the dizzy shaft and the jackshaft?

[MIG Wielder]

Ah yes ! Of course ! Thankyou. That must also mean the 2 gears are not a 1:1 ratio.
I'll see if I can work out what is going on just as a matter of interest.
Cheers for now,
Tony.