BSA A 65 Lightning


Monday, December 07, 2009 8:39:06 PM

Both BSA and Triumph made oil in frame models at the time their production was coming to an end in the 70’s, this design had 2 main problems. Despite both companies closing Triumph did manage a come back but sadly BSA was never seen again.

One; when the bike stood for any length of time the sump would fill with oil by draining from the oil tank, this equally applied to the conventional separate oil tank designs. The cause was gravity and an inadequate one-way ball and spring fitted between the oil pump and the crankcase.

The other, because of limited space for threaded pipe fittings the plumbing was push on rubber pipes clamped with hose clamps, as the bike got hot and because the pipes were right next to the crankcase so did the pipes and leaks then ensued.

Also, specifically on the BSA, the oil feed and return was through a triangular fitting that had a central bolt and 2 of O-ring seals,clamped to the underside of the crankcase.

For meanness, the BSA designers placed the bolt exactly ½ inch (13 mm) above a bottom frame tube, so that you virtually needed to remove, or at least lift, the engine to be able to replace the O-rings, this was another source of potential leakage, especially, again, as the bike got hot and the O-rings got hard!

My 1972 BSA Oil in Frame A65 was no exception!

The first part of my solution, whilst rebuilding the engine, was to have the bottom of the crankcase welded up where the above plate fitted and tap 2 of ¼ BSP threads, fortunately I found 2 of 90 deg. bends that I was able to screw into the crankcase and point in the right direction.

I say lucky, because the 2 threaded holes now in the crankcase were very close to one another. I then fitted normal hose tails and the same push on rubber pipe. Solution to that area, but still push on rubber pipes.

The next phase, how to overcome the push on rubber pipes and convert to crimped reinforced thread connecting pipes and install an external pressure fitting,that would not allow gravity to feed oil into the sump but would allow the suction force of the oil pump to overcome the ball and spring.

Space is very limited between the bottom of the crankcase and the frame tubes and from the oil tank (frame down tube) and the crankcase.

BSA A 65 Lightning

At the bottom of the oil-in-frame oil tank is a steel plate which when removed allows for cleaning or replacement of the oil feed filter,

the hole in the top of the filter fits over a steel tube, oil supply, which exits a the bottom of the oil tank (frame down tube)

The plate also has a drain plug for oil change purpose.

There is not enough room to fit the external pressure fitting between the oil feed tube before the rubber tube passes under the engine and certainly not enough space between the engine and the frame even though the pressure valve is only 22 mm diameter.

My solution was to fit a steel pipe through the base plate and up behind the oil tank base, terminating with a male thread, so that space, although tight, allowed for all the required fittings

Then it was a matter of measuring, making the in-between pipes and fitting them.

All the fittings and modified base plate

A view of the completed solution, not the only one? but it solved all the problems,

BSA A 65 Lightning
BSA A 65 Lightning
BSA A 65 Lightning
BSA A 65 Lightning

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