I have a Mini Olympus 2:3:1 gearbox (speed 400) that seems to have a 'rough spot' every couple of rev's it wants to hang, I've looked at both gears and there aren't any burrs.... maybe there is another gearbox out there that is of a better quality? Any help would be much appreciated!!

hercules,
Just a couple of thoughts,Does the motor run ok separate? Are the gears running true on thegearbox? From the side no up and down movement, could be a bad shaft or, gear not on shaft straight, causing a bind.
BJ

BJ, all apear to be straight and lined up, upon further inspection there were a few small feather pieces of plastic on the pinion gear that I removed, applied some teflon powder ran it again with the Grumpner 9x5 prop (Speed 400) seems to run smoother, but alot of vibration! Gearboxes are new to me, do they all vibrate this much? This is going in my HL Super Cub, wich is a fragile airframe to begin with....any thoughts, ideas would be much appreciated! Thanks, Eric