crankshaft shimming

[Jordan]

Hi Bruce, didn’t feel left out, just adding some pieces to the puzzle. It’s good to know how the factory originally assembled systems; perhaps there is a good reason for it. But then you have to deal with what you’re presented with. In your case, standard assembly was not workable. It would certainly occur to me to add shims on the timing side of the crank if I had run out of adjustment on the lower bevel drive gear. Any number of ways the adjustment could have been lost in an engine with miles on it. Matt

I generally agree - more than one way to skin a cat, if needs be.
I hear some people like to delete the centre gasket, which would change things too.

[machten]

I coincidentally happened to come across my notes for my recent 450 engine rebuild where I recorded shimming in the engine as I stripped it...this isn't the first rebuild of this motor though..

IMG_1499 (768x1024).jpg

Kev

[Geordie]

This is my first vertically split crankcase build and the comments above were most helpful. I have worked out a method to be happy with my rebuild:-

1. Align the crank so the con-rod is central to the cylinder mouth.
2. Shim the drive side to take up all its end play on that side.
3. Fit the bevel gear to the crankshaft and shim behind it for a close gear mesh but without it pulling the crank toward it. I used a DTI, bolted to the case, to determine that.
4. Measure the end play in the crank on the timing side - determined by the DTI.
5. Shim that end play out less the desired end play. (The Clymer and Italian manuals state 0.03 to 0.05mm.)
That will ensure end float pressure will always be on the thrust washers and not on the bevel gear.

The con-rod will only be off centre by whatever the total of the drive side shim(s) dictated. (Lacey Ducati has them listed at 0.2, 0.25, 0.3, 0.5 and 1.0 mm) The little-end side clearance to the piston will accommodate any off-centre.
The alloy cases will expand at running temperature more than the steel crank. That will move the lower bevel shaft gear toward the crank bevel gear. The 0.03 to 0.05mm is presumably that required to prevent tightening of the bevel meshing (I'm guessing ) and resulting in side loading of the bevel shaft thrust bearings.

Mouth.jpg

Zero.jpg

Endplay.jpg