A stock motor is usually a 27turn motor........
When i mean stock its stock.......it usually has more torque then speed......for your 540 application theres really no need to use a high rpm motor since its going to be fast in a micro anyway........This is straight from Aktions site...so please read and then you will understand.
Every motor is different. Because every motor is different, every motor needs to be geared accordingly in order to make it run it at its maximum potential without exceeding its limits at the same time. A good general rule of thumb to go by is gear up for stock motors and gear down for modified motors. The lower-turn motor you run, the smaller the pinion should be. That having been said, you might not want to run a 35T pinion on a 10-turn modified motor. The result would be not enough low end, and the motor may never completely wind out resulting in poor top end as well. You could also damage your motor and your cells by overgearing your motor.
By the same token, a stock 27-tun motor with a 26T pinion would probably be undergeared. In other words, you wouldn't be pushing the maximum performance capabilities of your motor and your setup would suffer. You'd have too much low-end torque and not enough top end. Pretty much the opposite of the overgeared modified motor scenario mentioned above. It is imperative that you find the right gear ratio for your motor and your driving style in order to get the best performance out of your Micro Hybrid.
First rule: always start small. There is no harm or foul in running a pinion that might be a tooth or two too small. A 27T-28T pinion is a really good place to start with any motor. Now you bigwhig 1/10th scale guys are breaking out your calculators and doing the math and realizing that amounts to a gear ratio of only 2.15:1! Who in their right mind would gear any car to 2.15:1? I will tell you...Micro owners! There are two other factors that allow such a high gearing (compared to your average 1/10th scale car): one of them is weight. The average weight of Micro Hybrid with all the electronics, a 6 cell pack, and a hefty 540 motor is around 23-24 oz. That's about half what a fully equipped TC3 weighs.