I have a spare engine for my 78 dt400 that I'm thinking about tearing down and rebuilding. The trans needs some attention because it is just about impossible to shift. Another problem is that the whole clutch basket has a significant amount of play both up and down and when I pull in it and push it in. What could cause that?  The clutch is torqued to spec so its something more complex than a loose bolt.

I think I might know what might be causing the problem. Could the bearing at the opposite end of  the shaft that the clutch attaches to be shot? The one proximal to the clutch isn't missing any balls or anything but should probably be replaced too because that is probably contributing to the in and out play of the clutch. Could that also cause my hard/difficult shifting?

On this diagram it's part # 12

http://www.bikebandi...m7104#sch213659

The clutch slipped all the time despite new plates and a used basket in great shape. It was caused by the in and out play the clutch had. If I adjusted the clutch so it wouldn't slip it would not disengage all the way. The transmission never produced any metal shavings during multiple oil changes in attempt to remove the clutch friction material sludge that was present in the trans. I'm hoping I can save this trans because the engine itself is in good shape and has great compression. I'd like to try to port this spare engine or at least have a functional spare engine for my bike.

Edited by 79yamdt, 16 March 2012 - 12:58 PM.

If it isn't the clutch bearing it's self i would venture to say you have some good wear in the tranny.  When i had my 82 RM250 apart my shift forks were worn like crazy. and the other bearings... your just going to have to open it up. I believe you will need a case splitter tool and a crank puller tool. And for how cheap they are you might as well throw in new main bearings and crank seals.

good reference
Motorcycle bottom end rebuild part 1 (of 3) crank & bearings