Scooterotica

Hi all, I'm currently putting together an RB motor, and I noticed that the crank was stiff to turn by hand once the front sprocket was asembled. I stripped it all done again, and, if I assemble it without the oil throw washer, it's fine, and turns nice and free. Any ideas, as to what the cause could be please guys?
Thanks in advance, Pete.

The seal retaining plate is a possible suspect, I had problems with mine not being fully seated on a recent TS1 build which didn't reveal itself until I torqued up the front sprocket bolt Also, check nothing is fouling on the mag side (see if it's still stiff with the flywheel off).

Is the drive side bearing completely home? If not, the back of the washer could foul on the chamfer in the crankcase. Or is the washer distorted in some way?

Hi, I did suspect it was the flywheel side, so I whipped that off 1st. It's ok with the washer off, it turns freely as it should do. Should the bearing and "shoulder" of the crank sit flush? There is a few mm between the two, and I think the washer may be pinching when the drive sleeve is tightened.

10", without looking, I'm fairly sure the washer is clamped between the inner race of the bearing and the drive sprocket sleeve, so the few mm of difference you mention with the crank shouldn't matter (someone please correct me if this is b@11@x!). Are you sure the back of the washer isn't rubbing on the crankcase?

Hi, I'm going to check that the bearing is fully home. I'm sure the washer is rubbing on the casing. I'll report back in due course. Thanks guys.

Ok, I've taken the crank out again and checked that the driveside bearing is full home, which it is. I've fitted a very thin spider shim between the bearing and washer and tightened down the sprocket. It now turns as it shoud do, with only the resistance of the oil seal noticeable. Would it hurt to leave this shim in place, or could it cause me a problem? I could use a thinner oil washer to help with chain allignment. What are thoughts on this please? Thanks inadvance, Pete.

Hmmm... If the drive side bearing is fully home, and the crank is free with the sprocket bolt tight with a shim taking the place of the washer, it must be the washer itself... Maybe try another one as a quick check? The washer is obviously there for a reason, so I wouldn't just replace it with a shim without someone with experience of this ok-ing it.

EDIT Just though, the chamfer didn't get damaged in some way during the build? Is there a burr or obvious high spot on it??

I've ordered a new washer today. I've still fitted the oil washer but with a thin shim underneath it to space it away from the casing. I'm hoping the new one will fit without the shim under it.

Sorry, misread your post (ie you hadn't replaced the washer with a shim as I said, you had fitted a shim UNDER the washer to space it off the crankcase). Good luck with a different washer.