I built a longtail from the madmudmotors (ebay) plans. The motor worked good the one time i ran it. when i disassembled it to paint my engine and do a few final touches to the motor, i noticed my u joint was missing one of the retainers (not sure exactly what the part of the u joint is called, but its what you press in and put the clip on to connect the two yokes), and it had come out. I have no clue where it is. I found the clip on the other side of the joint, where there were two clips where there is supposed to be just one. All i can figure is that I somehow put two clips on the same spot and forgot to put a clip on the other, or that somehow the clip came off as it was spinning and ended up hitting the spinning u joint just right to where the clip ended up clipped on the other side. I don't know how the thing didn't fly apart, luck i guess.. anyway, now i noticed that one of the yokes has a crack in it. This makes me worry about the u joint. It is from driveshaftparts.com, 3/4" shaft with 3/16 keyway with setscrew. I think it is rated for 1600rpm or so. I know that these motors run at 3600rpm, so is that u joint safe to use? It is what is suggested on the plans and also what it looks like most people use, but the crack in the yoke got me worried. Any advice as to what u joint to use would be appreciated. I was thinking about just ordering another of the same kind and hoping for better luck.

Th ujoint is a pressfit in the yoke ears, and the CLips are JUST IN CASE, but a cracked ear is something to worry about because it cannot hold a press fit as well and can sling out the ujoint cap. i'd look at getting a replacement.