9. BSA A10 Begin the Big End

It's time to start rebuilding the BSA A10 engine!. Having spent hours and hours on the buffing wheel, on the two crankcase halves and having obtained all new bearings, cam shaft, cam followers and oil seals, I started by assembling the crankshaft. The new big end bearings that had arrived were too small and turned out to be for the "small journal" type crankshaft. I returned them and received the correct ones and they fit the re-ground crank perfectly. The big end nuts were the next problem. The ones that I removed were the "self locking" type, but were so short that they lost half of their height into the recess on the con-rods, making them impossible to get a socket on them. I bought new nuts which had raised collars on them which lifted the hexagon high enough to torque them up properly. I then centre punched the threads above the nuts to prevent them coming loose.

I then pressed the new timing side bearing into the crankcase by heating the case and freezing the bearing and then pressing them together. Once fitted the bearing had pinched a little and it needed a final hone before the crankshaft would turn in it easily.

This done, the crankshaft was offered into the crank case and the second half of the crankcase was fitted. It was then possible to measure the crankshaft end float with a dial gauge. It turned out that the replacement crankshaft had less end float than the original and so needed one less of the shims fitting than the original.

The case could now be split again and the cam shaft fitted and then the two halves were given a liberal coating of blue sealant and then clamped together. The engine would now fit in the engine stand that I had bought, so that I could work on it in an upright position. The original pistons were re-fitted (which were in excellent condition) and then the barrel was next. Or so I thought. Sliding a barrel over one piston while squeezing the rings in carefully is difficult. Doing it with two barrels at the same time is impossible. So I decided to make some ring compressors. Two strips of thin aluminium wide enough to cover all three rings were bent around the pistons leaving two right-angle tabs where they came together. These tabs were drilled and fitted with nuts and bolts to do the squeezing. I slipped them over the pistons and tightened the bolts just enough to squeeze the rings without gripping them tightly and then rested the barrels on top of the clamps and pressed down gently. It worked a treat and the barrels slipped over the rings and into place. I was basking in my success when I realised that I had not fitted the cam followers inside the barrels before fitting it and so had to take them off again and the repeat the procedure.

Now with the crankcase together and the pistons and barrels in place, the engine was getting quite heavy and I felt that this was a good point at which to offer it into the frame. But how to do it without scratching my new, and still quite soft, paintwork. I came up with a plan!.

Having fitted the new chromed front engine mountings, I placed a piece of thick felt on the bottom  frame tubes and a piece of plywood on top of that. I then rested the engine on the plywood and tilted it until the top front engine mounting bolt lined up with the frame. In it went and I now had a pivot. I could lift the back of the engine, pivoted on the bolt and remove the wood and felt and then lower it until the second front mounting bolt went into place. It was in!!


I then added one of the newly chromed rear engine mountings on the left side and the Super Rocket engine was secure.

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 Copyright K. Hopcroft 18.08.12 All rights reserved
 You can contact me on: hopcroftscoot@gmail.com

My Other Blogs:

1961 Ariel Arrow Super Sport Motorcycle :
http://60sclassicmotorbikes.blogspot.co.uk/2014/01/1961-aerial-golden-arrow-restoration.html

Miniature Land Rover Defender:
http://miniaturelandrover.blogspot.co.uk/2016/02/1-miniature-land-rover-defender-idea.html?view=timeslide

1971 VW Karman Ghia Convertible Car:
http://karmannghiarestoration.blogspot.co.uk/2017/03/1-karmann-ghia-retoration-project.html

Motorcycle Trailers / Caravans:
http://motorcycletrailersandcaravans.blogspot.co.uk/2018/01/1-motorcycle-trailers-problem.html