crankshaft shimming

[flanker]

I've read a lot of threads and I like the idea of putting the cases together without shims, then measuring the clearance, and finally adding shims. Do I shim both sided of the crankshaft equally? or just one? Sorry if its a redundant question.... Thx Robert

[Rick]

deleted- see below
Rick

[Rick]

deleted- see below
Rick

[Rick]

Correction- I was wrong about the primary side crankshaft nut pulling the crankshaft into the crankcase- looking at a crankshaft this morning I see that the nut just secures the primary gear and rotor to the crankshaft, but there isn't an unbroken like of contact to the inner race of the main bearing.
I'm working on a couple of other, non Ducati, engines, and got confused.
Rick

[ecurbruce]

Hi Robert,
Since no-one else is responding, I'll take a stab at it, maybe it'll shake out some discussion...
To take an empty measurement and then fill the gap that much is a good starting point. After that put on a dial indicator to set the end play to zero.
All of the shimming measurements are done with the center gasket in place and bolts tightned.
Concerning which side the shims go on, several things determine how many to put on which side. Somebody here has a good method for finding how and where to center the crankshaft relative to the cylinder bore. The other thing to be concerned with is the alignment of the lower bevel gear set. As the crankshaft moves side-to-side, it changes the alignment of that lower bevel set. At some point, moving the crank too far to the points side, will keep you from being able to align the mesh of the lower bevel set. All of that has to be looked at together as the operation of shimming the crankshaft.

But before you do all of that crank shimming, you should set up your transmission in the cases with the crankshaft out... so you can look down inside the cases through where the crank resides and visualize the transmission gears.

Bruce.

[Jordan]

The Ducati books don't show shims on the right hand side of the crankshaft.
I think it'd be possible to put a shim there, but doubt there is any advantage.
A little bit of off-centre of the con rod with respect to the piston or crankcase centre line would not be critical, I think.
There is some side play between the con rod small end and the piston, and you won't run out of clearance there.
The bevel gear on the right side can be afterwards shimmed to provide correct location for it.

A method to measure crankshaft end play on a Ducati bevel engine, that I saw a mechanic use:
A flat steel plate was screwed to one side of the assembled engine, minus the timing gears.
A dial gauge mounted to a magnetic stand was attached to the plate, and used to measure the play when the crankshaft was moved from one side to the other.
If the crankshaft is too tight for this to work, the bearings can be removed and fine abrasive cloth used on the shaft to permit the bearings to slide. That's as per the Ducati workshop manual.

[machten]

Checking end float....as described by Jordan...

IMG_1621 (768x1024).jpg

Kev

[Jordan]

I see Kev has found another use for an exhaust nut tool.

[machten]

Ducati special tool number 6327-2!

[ecurbruce]

Hi Jordan
Jordan says,"The Ducati books don't show shims on the right hand side of the crankshaft.
I think it'd be possible to put a shim there, but doubt there is any advantage."

As I shimmed my crankshaft in my 250 nc, putting all of the shims on the primary side, I ran out of room to bring the vertical lower bevel gear inboard far enough to get a good mesh with it's  lower horizontal counter-part. I had to remove enough shims from the primary side of the crankshaft and add them to the timing side of the crank, to move the  crank toward the primary side and give the lower vertical bevel gear the opportunity to move in more underneath the lower horizontal bevel gear, to make a proper alignment mesh. At that point I could add a couple of the thinnest shims behind the lower vertical bevel gear, and get the mesh correct.
I had my crankshaft rebuilt, using a modified 350 big-end pin, which may be the reason for the alignment issue, I don't know for sure... and this may not be an issue on a stock (non-modified) crank and cases??.

Bruce