I'm trying to replace a broken motor coupling. I have the right factory part (#285753A), but it looks like the holes in the 2 metal sleeve lined plastic couplers are just a smidgen too small. I tried exchanging them for another set but the new ones are about the same size.

They only go on the motor and transmission shafts a little over 1/2 way, even with careful tapping and a bit of lithium grease to help things along. Is this typical? ...It doesn't look like it would hold up.

All the videos I've seen online - including the one on this site - appear to show those parts close to flush with the shaft ends when installed. The original all plastic version found on the motor was originally flush mounted (I don't know about the original one on the transmission since it was broken).

What's the deal?

I think you're right ...that's exactly what I ended up doing.

After greasing the transmission shaft, I had to carefully tap on the edges of the socket with a small hammer a little at a time all the way around - and occasionally in the center of the socket - until the coupler was flush.

As for the motor, propping it up vertically with wood blocks on two sides helped. I used the same technique on it but with a small wood block between the hammer and socket. This seemed to help and I think it also softened the impact a bit.

Going slowly like this took the better part of an hour but I didn't want to risk damaging anything. I was rewarded with a working machine.

Thanks!