crankshaft shimming

[machten]

Bruce,

Are you saying you had to take lower bevel shimming into consideration in shimming the crank?

Kev

[ecurbruce]

Hi Kev,
Yes, don't know if my crank just needed too many shims, or just what, but by the time the end - play was to zero, the crank was too far to the ignition side for the lower vertical bevel gear to go far in enough to mesh correctly with it's mating gear. In your experience have you ever run into that before?

Bruce

[double diamond]

Every lower end I’ve ever disassembled had the shims on the primary drive side. If you add shims to the timing side it will affect the lower bevel shimming which will have to be re-set accordingly. Matt

[Jordan]

It did wonder if the bevel gears could influence shimming options, but thought that surely Ducati would have arranged it so all would be well, as long as the standard fitting procedures were followed. Why complicate things? Having shims on just one side meant faster assembly at the factory.

Could it be that the bottom bevel gear on the short vertical shaft had been fitted lower than normal (with its own shim arrangement)?
That could require the crankshaft bevel gear to be installed more to the left to make room for it.

[ecurbruce]

Jordan says," Could it be that the bottom bevel gear on the short vertical shaft had been fitted lower than normal (with its own shim arrangement)?
That could require the crankshaft bevel gear to be installed more to the left to make room for it."

Ooooh, but it didn't stop there...
I had to re-shim the lower half tower shaft to get the lower horizontal bevel gear to mate the now reshimmed vertical bevel gear, and so on right up to the cam, re- shimming the whole way...I think it was more about the rebuilt crankshaft dimensions and new ngk bearings being somewhat different than the original parts. It all translated to getting the crankshaft in the correct position for the bevel gear faces to mate perfectly to eachother. That shoulder on the right (timing side) end of the crank that the bevel gear can rest against has to be far enough to the left for the bevel gear to get under the tower shaft (and still ended up with a couple of the thinnest shims behind it in my case). In other words, in the beginning my lower vertical bevel gear was sticking to far out and loose against the lower horizontal bevel gear, and had no more shims behind it. Shimming the lower half of the tower shaft down against the vertical bevel gear would have created a situation where the two gear faces would have been quite offset from eachother. (you know, at the ground- in mating surfaces of the two lower bevel set...)

You know, thinking it all through again, I'm guessing my rebuilt crankshaft must have come out a little narrower than an original crank, making more shims necessary...maybe?

Bruce.

[ecurbruce]

Hi Matt, didn't mean to leave you out
Matt says," Every lower end I’ve ever disassembled had the shims on the primary drive side. If you add shims to the timing side it will affect the lower bevel shimming which will have to be re-set accordingly."

I understand what you are saying is standard,,, and (but) I was counting on the fact that I could reset the bevel set after adding shims to the timing side of the crank. That's what I needed from the shims on the right side...

Bruce.

[Jordan]

I had to re-shim the lower half tower shaft to get the lower horizontal bevel gear to mate the now reshimmed vertical bevel gear, and so on right up to the cam, re- shimming the whole way...I think it was more about the rebuilt crankshaft dimensions and new ngk bearings being somewhat different than the original parts.

Non standard sized parts would be an explanation for the problems.
Should not have affected the top bevels though.

[flanker]

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.

thats a great idea!!! IF i visualize the gears am i just looking for function and "shiftability"? I had no shims on the timing side when I took it apart. but I replaced the bearings, which are so smooth now. So I'll have to see how it all lines up.

[flanker]

It did wonder if the bevel gears could influence shimming options, but thought that surely Ducati would have arranged it so all would be well, as long as the standard fitting procedures were followed. Why complicate things? Having shims on just one side meant faster assembly at the factory.

Could it be that the bottom bevel gear on the short vertical shaft had been fitted lower than normal (with its own shim arrangement)?
That could require the crankshaft bevel gear to be installed more to the left to make room for it.

I sorta felt the same way, but was wondering if it would be smoother with a shim btw the bearing and crankshaft on the timing side. I guess I have to see how it all lines up!

[double diamond]

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