Whats the easiest way to install the pinion on the motor shaft? Warm up the pinion?

Can you at least tell us what model you have?

I've got the Shogun V2, belt drive, Justgofly 400DH brushless motor with a Castle 35 and a Thunder power 1320 LiPo

You need to buy a tool for it, if you don't it will be difficult to do without messing something up. They are avaible at many hobby shops or search google for "gear puller 1mm." You may want to substitute the shaft diameter of yours for the 1mm, but even with 1 mm it will bring up smaller gear pullers.

Hi,

I'm sure there is a more preferred way, but I just use my bench vise. I hold the gear on the end of the shaft and slowly crank the vise in. IMPORTANT! Make sure the other end of the motor shaft and the gear is the only two points that contact the vise jaws. If you push against the motor can you will damage something!!!

MrModfi

Expanding the pinion gear with a torch or soldering iron will make it easier to fit on the shaft.

Arbor Press.

I love mine.
Also, you don't want the gear pressed until it is flush with the drive shaft. Get some micromometers out and measure it before you remove the old one. So you get mesh correctly. If you don't have micrometers, then get a piece of tape or something.

Get the tool will save u time and u will not have to worry about damage my .02 cents http://www.modefosheli.com/inc/sdetail/294