Engine Rebuild: Part two - June/July 2018.
Here is a brief summary of what has happened so far:
The crankshaft (above) has been crack tested and found to be fine, I had two others tested and both were unusable.
The pistons have cleaned up nicely and can be reused. Because of the previously mentioned wear the top ring land had to be machined out to take a larger ring. New rings have now been fitted to all pistons. The bores, as we expected, are fine and only needed to be deglazed.
Fitting the new Cavalitto big end bearings proved to be a bit of a challenge as when pulled up tight the rods were up to 0.0015” out of round. Rob spent a lot of time tweaking the bearings to get a perfect fit.
For the crankshaft mains both end bearings fitted perfectly, the centre however was about 0.0015” out. The photo of the block shows where in the past it has had a large welded repair at the centre bearing mount, measuring this found it hadn't been machined dead square, Rob has now adjusted this so all three bearings now have a perfect fit.
Now some bad news, good news! The crankshaft was taken to Balancing Services Australia to get balanced. When it was placed on the machine in Murray Johnson's words, “it just about leapt off it was so far out of balance”. Now this could be considered a bad thing but for me this is a good thing as I've always thought the engine ran rough and out of balance, the initial reason to get his work done.
The other bad news was the crank had been lightened so much in the past there was not enough metal left to re-balance it. Murray attached some temporary weights to assess what was needed, 65 grams will have to be added, he checked it with the flywheel and this was found to be fine. He had problems getting the clutch pressure plate to located accurately each time, eventually he'll drill and fit roll pins in three spots to ensure it can be mounted in the same exact location. In the meantime Rob has collected the crank and is making up the appropriate weights.
Once all this is done the crankshaft will be back to get balanced then a simple matter for Rob to re-assemble the entire bottom end before I tackle the rest of the assembling!
Below: Rob Miller's workshop and my Aprilia block on the line boring machine.