Clutch boss locking up on rebuild engine

[Eric_TZR_TDR]

Build my first engine . Closing the upper and lower casing was quite exciting. But everything seemed to go well. Crank as well as gearing were free turning with little resistance.

During assembly of the clutch I noticed some resistance in the center clutch boss. Didn't feel right. In the end started comparing movement with an old engine. Clutch boss on the old engine was free turning. Even when the clutch boss nut was tightened. With the rebuild engine there was resistance once the nut was tightened. Even by hand. Turning it to half of the adviced 90 nm and the center boss was locked solid.

I have changed baskets and all parts connected to the main axle but the problem stayed. So problem is related to main axle inside of the rebuild engine ?

Does anyone have an idea what can be the cause the clutch boss locks once the boss nut gets tightened ?
So I know were to look for when opening.

[4l04ever]

Not sure if this engine has one, but there is usually a spacer/washer behind the basket, and also one between the basket and the hub.

[teezer250]

4l04ever is correct in what he says.
I had the same problem last year when i had to put a second hand gearbox along with new shaft bearings due to a collapsed gearbox output shaft bearing wrecking the original gearbox.
The clutch boss was locking solid at 90 nm.
I spent a full day messing about trying to determine the problem checking everything as stated below.
I then replaced the whole clutch assembly including the 2 washers with one that had done 4000 miles and still had the same problem as yours.
I then kept lowering the torque settings by 5 nm at a time until it spun freely at 60 nm and left it at that.
Nothing has been left out of the engine when rebuilt and nothing missing.

Never worked out the reason for it locking up at 90 nm.
It could be the splined washer that sits behind the clutch boss (47X-16164-00 ) is worn down a little but both measured the same.

[Eric_TZR_TDR]

Thanks for confirming I'm not crazy 
I have both washers. I have exchanged all parts on the main shaft and only have problems on one with both configurations.
So I expect some kind of wear on the main shaft. Will try to do some measurements.
And lesson learned. First asssemble completely without threebond to test clutch before sealing.
To be continued !

[teezer250]

I doubt it will be wear on the main shaft,if the washer has worn thinner,then the gap between the boss and the outer basket will be less possibly causing binding between the two parts.
Hopefully a new washer would fix it.