Rm 125 crank problems

[Nipper]

I am after some advice with a small problem I am having reassembling a RM 125B motor.
With the crankcases together the crankshaft turns freely, but as soon as I start to tension up the engine case screws the crankshaft becomes difficult to turn. It will still rotate but there is a noticable difference ,it doesnt turn anywhere as free as it should.
What do you think I might be doing wrong? Cheers..

[TM BILL]

When its assembled give the crank a sharp knock on both ends of the crank with a copper mallet , to centre things up .
If that dont work check the assembled crank width against factory specs .

[SUZUKI311]

The crank is binding up in the main bearing in the side of the cases which the crank went into first,-assuming you have gaskets in place etc. Again assuming you have warmed up the mains/cooled the crank when you assembled the crank into the cases, put the nut on the end of the crank which went into the cases first, and lightly tap the end of the crank with a copper hammer. This will move the crank away from the shoulder of the main bearing a little, and the crank should spin freely. DO NOT hit the end of the crank hard, with a steel hammer, or without the nut being on the end to protect the threads on the end of the crank. Hope this helps.

[Nipper]

Thanks guys ,I am heading to the shed now. appreciate the advice.

[Nipper]

Worked a treat, thanks again.

[pancho]

 Having done that, check side clearance on the big end.
 With a parallel crankpin you need spacers placed between the flywheels to prevent the the flywheels moving along the pin during assembly and reducing the clearance.
Cheers pancho.