Bull & Pinion Gear Tooth Counts on OC4s

[oliverchris]

Can anyone supply me with the tooth counts for OC4s and the approximate date they changed? I have seen some with OC3 set-ups. And I've heard of 'mongrels' with different gear set-ups on each side! I guess so long as the ratio works out the same, the machine will not veer to one side  
Here's what I have so far from parts manuals:
Early four cylinder models Bull 119 142 Pinion 117 600 [72/15 like OC3s???]
Early 3 cylinder models Bull 607 799 FS [67 teeth] Pinion 603 829 F [14 teeth]
Later 3 cylinder models Bull 610 817 FS [58 teeth] Pinion 610 711 F [12 teeth]

[Robert Barbour]

The ratio's for all three different gear sets are very close so any of them can be used.   I have often seen machines with different gears in each side.  The set with fewer larger teeth would be the strongest, the ones with more teeth would be produce the least noise.  As if that is a concern!!

[hotratz]

My '57 has the 72/15 ratio