19t gearing
 

any one know what gearing is best for a 19t or a 12 double please :D

19T or 12 Double hmmmmm.

12 Double: 23/24 tooth pinion would seem a good place to start.

19T: I really have no idea in the D4. The below advice is purely based on TC running but should hold true.

A lot depends on the make of motor.
Orion: Look for an overall ratio of about 7.00:1

Anywhere from 6.8:1 to 7.8:1 depending on how revvy ot torquey the motor is...

Having run a 19T a couple of time recently in buggies I've found that they don't pull a big gear like they can in a tourer, the extra weight and the need for more rip off the jumps seems to defeat them.

I would gear the 19 1 or 2 teeth higher than your 12. For comparison I have been running 19s at around 9.5:1 overall in a buggy. This is indoors by the way.