Super Jet Difference between drive couplers?

[lostcreek21]

I'm putting together a 96 RN with some parts from a SN. During the swap I realized that the drive coupler from the SN did not fit the RN midshaft. So I bought one off a member here and the one they sent me is too large now. I thought there was only 2 sizes for superjets?

 

[JetManiac]

The couplers are specific for midshaft or engine side and have different sized threads.

In general, all engine side couplers are the same size, but some very early 650 cranks had a smaller size.

The midshaft couplers are the same on all 701s and most 650s, but some earlier 650 midshafts had a smaller diameter coupler threads size.

All a/m coupler sets use the larger midshaft and engine coupler thread sizes.