Rocker Pipes / Banjos New Parts Nightmare! SOLVED + Photo

[Peter Gee]

So I got a set of new pipes and the new correct BSA Bolts   65-0317             from a well know supplier in UK. I have fitted these and noted the bolts have a tapered Under Head profile, but do not take Fibre washers, so I presumed the action of tightening onto the also new rocker pipes would form a tapered oil-tight joint. So without overtightening (about 12 ft lbs) I did so and then tried 25 lbs of air.

Each union has a predominant air leak, which will translate into an oil leak. Ideal would be alternative bolts with a wide flush face, so one could fit a copper or fibre washer under them.

Or should I tighten much more (did not want to deform the banjos)?

What have I done wrong or if nothing, what is the solution?

My guess is modern banjos have not been made with the correct taper angle perhaps?

Or maybe this job requires special fettling and fitting to get each anjo super square and centralised, though one thought the slight taper would have done that!

[bsa-bill]

That gap looks a bit big to my eye, you may have the wrong bolts ( there are other similar bolts, for Goldie tank breather for instance ), but
I'm not sure that 25 lbs per inch of air might be more pressure than the return oil feed to the rockers is normally, others will know I'm sure, I'd be tempted to try it with the oil feed and if it still leaks try a bit (tad) more torque

[Peter Gee]

Thanks, the bolts have the correct very small drilling, not the larger Goldie ones.

IMO if there is any air leak i will certainly become a large oil leak quickly..in this instance I can easily feel it/hear it   blowing out of each rocker banjo/bolt

[RDfella]

Are they the right pipes? The singles pipes are tapered because they sit on a tapered spindle, but the twins sit against the head and I thought they were flat. But then I may have remembered wrongly from when I did my A10.

[JulianS]

Twin its flat against the head and taper against the banjo bolt. They usually seal quite well.

[bsa-bill]

the bolts have the correct very small drilling, not the larger Goldie ones.

OK but I was referring not to the Goldie rocker feed bolts but to the bolt that holds the vent pipe onto the Goldie or RGF fuel tank, could be it has a different taper but if you ordered a pair they should not be two of it

[RDfella]

I am confused. Do your pipes have a flat one side and a taper the other? Looks to me as if you have a taper banjo bolt up against a flat pipe, which is wrong.

[Swarfcut]

 Yes , the banjo should have a flat side facing the rockerbox, and a tapered side to match the feed bolt taper. A thin fibre or soft metal washer sits between the flat face of the banjo and the rocker box. It locates on the 1-2 mm of plain rocker shaft that protrude from the box. The new feed bolt taper and the banjo taper should obviously match, so check that the finish here is OK. The banjo may need a bit of a tweak to lie flat against the rocker box. With all in order,  good matching tapers with perhaps a dab of Loctite will give a  good oil tight joint.  Otherwise it looks like pattern parts that are just not quite right.

  A couple of things to bear in mind. The Acorn nuts should first be nipped up gently to draw the rocker shafts into the box until they seat and don't forget the washer under the Acorn nut as an additional seal. Check that the new bolt is not bottoming before it puts pressure on the tapers.....it may be a little bit too long. Standard bolt chosen from my stock has 16mm of thread, and measures 19mm from end of thread to start of the taper.

 Swarfy.

[Peter Gee]

The problem may be with the supplier...who listed the pipes as suitable for both A7/A10 and B31/33 when it seems this is maybe not the case? The part numbrers given  in the listing are 42-0048, 42-48. Hmmmm???

[Peter Gee]

I've googled the pipe part number for 'images' and some from CBS in USA are shown with the banjo in closeup, and it looks like the banjo taper is much more pronounced of this set, and the upper face of the banjo of thicker material, than the one I was supplied by a well known UK firm who claimed the pipes fit twins and singles...

[RDfella]

Peter, the B31 is different from the A series. It doesn't sit against the head but on the end of the rocker shaft. On the B series the banjo is tapered on both sides, whereas the A series is tapered one side only.

[RDfella]

Peter, just been thinking, were you talking about the banjo or the banjo bolt when you referred to B31 / A1O? They may be the same, I’m not sure.
But from your photo it looks like you have a tapered bolt against a flat banjo. So, back to basics – you have a twin banjo, flat one side, tapered the other? Before fitting, check bolt is a reasonable fit in the banjo taper. Then assemble with flat side of banjo against head, with fibre washer in between. If bolt does not go right home, then it needs shortening.

[Greybeard]

Peter, the B31 is different from the A series. It doesn't sit against the head but on the end of the rocker shaft. On the B series the banjo is tapered on both sides, whereas the A series is tapered one side only.

RDfella, I'm in awe of your knowledge, however, I need to say that on my Plungie 'A' the banjo's have an internal chamfer on both sides. The hole in the banjo is larger on the rocker spindle side. The rocker spindle is chamfered and protrudes slightly from the rocker box. The bolts are chamfered.

[Peter Gee]

I very much appreciate all the thoughts and help here...so from RD's posts, a supplier cannot claim that one pair of banjos will fit both plunger and SA  twins, but that has happened in the case of the (big) supplier I bought from.

IMO a taper  cannot mate with an edge, but only with his female (oops! :-) )

I illustrate here the CBS pipes. Mine DO NOT have the deep taper these have. The taper indicates a THICKNESS of materiel as well. Mine have simply a very slightly chamfered hole. A chamfer is not a taper.

My feeling is, I have lost 29 pounds and any other restorer with this  part to buy and choose should beware.

[ellis]

Peter Gee

You also need to be aware that on some Banjo assemblies the short pipework from the tee too the banjos are copper so are malleable. However i have had some where the long pipe is not copper so when you try to bend the pipe to fit to the frame tube are not and snap even after heating the pipe. I hope yours are OK.

ELLIS