How to pull a bearing out of a blind hole?

With the crankcases split, I decided to replace all of the bearings but one in particular was a problem as it’s fitted into a blind hole, so I couldn’t drift it out from the opposite side like I did on the others.


There may be an easier way but after a bit of head scratching I decided to try to make a threaded puller, that would go into the 15mm bore of the bearing and hook underneath the inner race. I started by turning a nut down to just under 15mm diameter on my friends lathe. I left a small step on one end at 16mm diameter for about 1 mm and then split the nut with a hacksaw, so that it would act like a split collet.


This also gives clearance, so the 2 halves will go into the inner race, with the step engaging under the bearing at the bottom. The plan is to screw a bolt into the split nut and hope it keeps the lip under the inner race whilst the bearing is jacked out.

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I then made a steel spacer with a 36mm counterbore to clear the 35mm diameter of the bearing outer race.


and the finished puller looks like this.


I heated the casting with an electric heat gun to expand the aluminum and reduce the interference fit a little. Then I quickly screwed in the bolt, held the head and screwed the nut down. After a few turns it started to turn easier so something was happening, either the bearing was pulling out or the split nut was pulling through.


and fortunately it was the bearing coming out – job done!


One step forward and none backwards; now that must be a first!









115 days to go to the Motogiro D’Italia…

and it’s turned into a full engine rebuild.

I’d hoped to get away with minor bedding-in but the list of issues has grown to the point where I can’t trust anything,

  1. Burning oil due to to non standard O rings being fitted in the wrong place on the valves
  2. Cylinder head gasket leaking oil due to poor head gasket alignment
  3. Overhead Camshaft bearings not running smooth
  4. Cam chain far too tight as cylinder gaskets were too thick (hence cam bearing problem)
  5. Slipping clutch with springs shimmed up and going coil bound
  6. Excess end float on clutch basket causing clutch to rub on Primary cover at one side and clash a little with the drive gear when it thrusts the other other way. (helical gears)
  7. Gearbox input shaft doesn’t turn as smooth as it should, so there could be a bearing issue in the gearbox.

So that made my mind up for me. Full strip and check everything.


And it’s just as well I did. The previous engine builder had a preference for using silicone for gaskets and like most people, used far too much. It then squeezes into the engine and can break away blocking oilways, leading to total engine failure. Not something I want to happen in the middle of Italy…