Advice for replacing a BMC V1 clutch?

I built my Dad an ebike with a BMC V1 motor running on a 36V 25A 6FET controller, and its clutch seized up during a ride. (The controller also fried.) So now I’m trying to decide how to proceed to repair the motor.

Here are my thoughts:

1. Purchase a new BMC V4 clutch assembly from EbikesSF for $206 + shipping?
OR
2. Purchase a new Mac clutch and a new set of Mac gears from EM3ev for $55 + shipping?
OR
3. Since I’m also needing to buy a new controller, maybe it makes more sense to just get a whole brand new kit, including a new motor? (This seems wasteful, but it might save me some hassle of adapting a new clutch that isn’t a perfect drop-in replacement, and also with matching the motor phase and sensor wires and connectors to a new controller(?).)

What would folks recommend I do here?

And with either of the first 2 options, would I face any difficulties in getting the new clutch parts (either V4 or Mac) to mate up properly with the V1 motor?
And is there any difficulty in assembling the separate Mac clutch and gears?

Thanks in advance for the help!

I'd buy a new DD kit for about $200 and never worry about clutches and gears again.
http://endless-sphere.com/forums/viewtopic.php?f=3&t=66302

The BMC V1, V2, and V4 cases are identical.

The BMC V1, V2, and old MAC gear clusters are interchangeable. The V4 cluster is a smidge wider and you used to have to leave off the outer circlip retainer, but a recent V4 clutch I mounted up fit nicely with the outer circlip by leaving off theprecision shims (I don't know it there was a production change or removing the shims did the trick...)

The new MAC gear clusters mate up perfectly in the BMC and the outside circlip fits properly. However, the assembled gear cluster is a trifle thicker and the outer tips of the gear teeth may rub lightly on the case. This doesn't seem to be a big thing, but be aware that there is about zero clearance. This might be able to be addressed by relocating the inner shim to the outside (it's that tiny an offset). Old and new MAC clutches are of differing thickness with attendant changes in the gears to match. Don't try to mix and match gears and clutches of different vintages or clearance issues can arise - buy gears and clutch at the same time.

I find the BMC gears to be slightly quieter than the MAC gears - they both use straight-cut spur gears and the MAC gears are a bit wider, so no surprise there....

Otherwise, both the newer MAC and BMC V4 clutches and gears are substantially stronger than the old V1 models that you had. I have BMC V2 motors and have run V2, V4, old MAC, and new MAC gear clusters with success.

Some notes on the gear cluster transplant here. Easy if you spring for the pullers. Spinningmagnets has a MAC teardown thread here - the BMC teardown is simlar up to the gear cluster removal. The only difference is that the BMC has oil seals on the shaft - be careful not to tear them when pulling the threaded shaft through... (lube the threads with grease).

Not sure why your controller vaporized, but if you get the gear cluster from EM3EV, get one of the 9FET models as a minor ungrade.

BTW - there's no issue with riding with a seized clutch - it's just sort of a geared DD motor. It doesn't roll super well with no power and eventually beats the heck out of the gear cluster key. So, you can swap in the controller and get on the road and then repair the clutch when convenient.... If your key is loose, get a short length of 5x5mm keystock from a power equipment dealer (lawn equipment, ATV, motorcycle) for a buck and cut/file a new key (not sure - maybe EM3EV can provide one...).