Well it's finally go time with my 996 rebuild. I'm at the A-Team third act, for those of you who didn't watch this show, the A-Team was always locked in some shop or warehouse that had all the tools and parts they needed to build a machine to make their escape in. I will be locking myself in the shop over the weekend, and hopefully riding out on my restored/rescued 996.
Did you heat the cases up to remove the old bearings?
On the left hand side case there is a bearing in a blind hole (I think it is 75791.1747 on your bike). Did you use a slide hammer to remove it like this one?
Yes I heated the cases to 100C when I pulled the old bearings. I used a drift to remove them. I have a slide hammer, but I didn't have a pair of jaws that would work on that blind hole. There is actually a couple of small holes that let me get a drift on the backside of the bearing, but it was tedious to remove.
Hey Jeremy,
Thanks again for getting all those little parts to me.
Yes on the squish and the cam timing.
I got my copper gaskets in .40mm which should put me right at 1mm squish.
The motor had offset keys when I took it apart, I'll see where things are at with the shorter deck height and all the new parts. I bought a used set of cam idlers, because mine showed signs of severe overheating from the bad bearings in them, they came with the cogs and some other offset keys. Hopefully I can get the timing right with what I've got, I'm getting tired of spending money, I want to ride!
-Josh
If you end up needing keys let me know, I can probably come up with some. For all that effort, you're going to want to take it all the way and get those things dialed. Just putting things where they ought to be really livens up a desmoquattro. Lots of free (sorta) power there.
Thanks Steve,
I had actually found this a while back, it looks like a great article, but I'm on a mac and don't have power point, so I was never able to watch the original how-to. I like those flex arm mounts for your dial indicators, they look a hell of lot easier to deal with than the lock joint arms I have.
The factory manual gives a pretty good description of the procedure fortunately.
I got majorly sidetracked this weekend, I found someone who wanted to buy my '51 Dodge powerwagon, and I had to get it all together. I hate to see it go, but now I've got a little more money to spend on fine Italian machinery!
Thanks again for the info.
This is not mine, but it's how mine was supposed to look.
Now back to the 996.
Well life is not an A-team episode after all. After multiple distractions, I'm back on the project.
I got the new bearings installed in the case halves and measured for my crank pre-load. I need to add .1639mm to both shims, which means I need a 2.2169 and a 2.2639. If anybody has a set of crankshaft shims that are thicker than these dimensions please let me know, I don't mind spending some time lapping them to size. I have a 2.053 and a 2.1 if anybody could use them.
I got lucky that I needed two thicker shims with the new bearings. This let me install my crank and take a direct measurement of endfloat with a dial gauge. This is by far the most accurate method.
I tried several other measuring methods just to compare, and they are never repeatable. If you measure ten times, then you get ten different results. The method the factory manual and the Haynes suggest, using calipers and a straight edge, is just about worthless to measure down to the hundredth of a mm. If you're trying to set a .15mm pre-load then your measurements have to be accurate to at least .05mm to end up somewhere between .1mm and .2mm.
Installing the crank with two small shims and installing four of the m8 case bolts, then measure endfloat with a dial indicator, this got me the same measurement every time, and that's what you want. If you don't have a set of shims that are thin enough to get a measurement, don't be tempted to just use one on the bottom, as the crank will hit the case before it takes up all the slack in the bearing on the end without a shim.
This was the best of these, but still not very repeatable-
Using a bore gauge might work. if you can make sure the bearings are pushed outward completely and evenly when you take the measurement-
I use a spreader clamp like this one to help split the cases apart, trust me this is a vital tool when you are putting them together and then taking them apart over and over, those dowels really grab when you're trying to pull the halves apart, this solves that problem completely-
One more thing, pamper your parts, especially machined aluminum and precision bearings, keep the dust out and make sure everything lays flat, if there are dowels then put something under the unsupported sides. This may sound like overkill, but there is nothing better than bolting up a motor and having no leaks-
One thing that I discovered, the parts fiche shows a .2mm shim behind the left side timing shaft bearing, #11. My case did not have room for this shim, I barely had room to get the circlip #13 installed. My motor did not have this shim installed when I disassembled it, so I was suspicious. Fortunately I measured and determined that the shim would not fit before I installed the new bearing. Never trust anything, even the factory manuals. Always verify and understand before blindly following instructions.
Are those crank bearings OEM Ducati, or aftermarket SKF?
They came from a local bearing supply, but seem to be identical to what was in the motor, same numbers and country of origin, and saved me about $50 just for the two crank bearings.
Many parts of a Ducati motor of that vintage are shimmed to tolerance, so it would certainly be worth setting the crank preload, making sure all the tranmission shafts are shimmed properly, etc.
With new bearings you'll have to reset the crank preload anyway, but it never hurts to check the work of others, especially if you want the best results.
When you use the word vintage, it makes me realize how old our bikes are already
Quote:
Originally Posted by CrimsonCloak
Many parts of a Ducati motor of that vintage are shimmed to tolerance, so it would certainly be worth setting the crank preload, making sure all the tranmission shafts are shimmed properly, etc.
With new bearings you'll have to reset the crank preload anyway, but it never hurts to check the work of others, especially if you want the best results.
Bearings in the freezer/cases in the oven
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