1968 B25 part 40-8477... WTF?!?

[MadPete]

Just as one thinks it can't get any worse, I tried fitting the GRP oil tank to my 1968 B25. The top two lugs and rubber isolators and bolts went on with a few attempts to get everything in the right place. It was hanging nicely when I wondered how to secure the base of the GRP oil tank.

In the base of the oil tank set back behind output pipe, there is a "hole" not deep and somewhat irregular in shape. This sort of matched up with a hole in the frame bracket under the oil tank. I don't have anything that came out of this area when I was dismantling the fittings many years ago. So I thought I should try to obtain one.

The 1968 parts book defines this item as "40-8477 grommet, lower" and it's not immediately obvious how this is fitted. A self tapping grub screw is specified... I presume the idea is to push this "peg" up into the recess in the oil tank and then use a self tapping screw into the side wall to keep it from falling.

The 1967 workshop manual says:

The tank is located at its base by a peg which passes through a rubber grommet, mounted in a frame bracket. A small self-tapping screw retains the grommet in its housing.

What is this "peg" made of - does anyone know or have an example (or photo of one). Is it some sort of plastic or rubber "finger" and how much restraint does it provide for the oil tank? And a self tapping screw to hold it? What is the experience of other members when refitting a GRP oil tank to a B25?

I note the 1969 B25 had a metal oil tank and a bolt/grommet combination - which I presume actually screws into the oil tank base. The grommet would provide vibration isolation/damping. Maybe I could use a combination like this with some lock nuts to position and hold the bolt that "loosely secures" the GRP tank...

[MadPete]

Having consulted with Mr Ratio's volume 2 - I note there seems to have been (apparently) a "peg" sticking from the base of the oil tank and that located into the rubber grommet in the hole in the lower bracket.

Not sure how best to restore the peg or what better strategy to use. Something to cure insomnia... :0)

[Kev D]

I've just looked at pictures of FG oil tanks  for sale. A lot seem to have the peg missing. A few do show a metal dowel sticking out though.
Whether it was originally moulded into the fibre glass or held in some other way isn't  obvious but it shouldn't  be too hard to fix something in place

[MadPete]

A useful observation. As @KevD says - some have a metal peg sticking down that engages with the rubber grommet on the frame lug. I suspect the pegs are "vibrated" off. In all the examples I have looked at, the oil tank just seems to "hang" off the top fixings. It is constrained by the moulding on the front of the tank that wraps around the frame tube.

After some discussion (and beer) with the local BSA enthusiasts the consensus seems to be that fixing anything on the tank to replace the broken peg is a lost cause. The best suggestion was to "open up" (ie drill) the fixing hole and (using a hot glue gun) use thermoplastic glue to fix a suitable diameter but short metal tube into the body. Nothing big or elaborate. Then find a bolt and some lock nuts that can be screwed onto the frame lug and adjusted to screw up into the reinforced mounting hole. If we can find a suitable rubber sleeve or thimble to "cap" the  bolt (where it secures the oil tank) to allow some vibration of the whole thing then that would be perfect.

The "peg" on the bottom of the oil tank should look like this:



The only problem is that it is a fiddly job and spatially hindered making it difficult to get the spanners in - which is probably why they chose a peg in the first place! For now I have left the oil tank hanging off the top mounting points.