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Hi, I'm new to the forum and I've got a 1974 R90/6. I got it as a basket case and have been gathering the missing bits. It's got a kick starter which I have ascertained is normal through 1974. I haven't been able to verify that the engine serial number is correct for it and I am trying to figure out if it actually has the right drivetrain. All sorts of possibilities are running through my head. It's not running yet, so I can't tell if it's a 4 or 5 speed. If it's indeed an R90 engine, is it possible that it could have a /5 trans on it? Any thoughts on this would be appreciated.

The VIN number should be stamped in the engine case above the oil filler and on the right hand gusset of the head stock. A four speed will have an aluminum shift lever, the five speed is chromed steel.

Yes a R90 could have a 4 speed in it. A simple swap. The 74 transmission was not a good one.

Would the 4-speed have the neutral switch on the rear cover plate, whereas the 5-speeds have the switch on the bottom?
I really don't know.

Thanks for all your input guys. As it turns out, I misread the engine number the first time, on closer inspection it is the same as the VIN. Yahoo!! It does also have a chromed steel shifter as well. So I guess I will continue on with no worries.

Well, as Duane mentioned, the 1974 5 speed transmissions with kickers are a one year only design which have a few known flaws. You may have no problems with it at all, but the actual kick start mechanism is one weak link and should not be used due to its tendency to shed metal bits.

Thanks, other than that are they okay?

Maybe OK, wouldn't be a bad idea to find a good used 1975-80 one to rebuild or keep as a spare...

Okay, I'll see what I can come up with, thanks for to advice.

The best thing to maximize the lifespan of an old gearbox is synthetic gear oil---Mobil 1, Amsoil, Redline, etc. 75w-90 seems to have been as good for mine as the specified 80w-90.