B31 Rocker Oil Supply Problem

[Foghorn]

I recently ad to remove the head on my B31 due to the loss of compression.  I first thought it was a leaking head seal so I lapped the head to the barrel and re-assembled it all.  But when I tried to set the tappets I found that the inlet tappet holder had loosened itself over time and rotated loose enough to prevent the inlet valve from closing at all.  So up came the head again enough to allow me to tighten the wayward holder which fixed the problem. BUT:
After I had re-assembled everything the engine started on my second kick and away I rode rejoicing.  When I got back after only say 3 miles, oil was pouring from the top of the engine- I think from the rocker supply connections on the head.  I think I failed to put a seal on the bolts where they screw the copper oil pipe to the rocker shafts.  Anyway, and here is the issue and the question, with no answer from any BSA manual of service instruction that I have.  The two supposedly identical bolts that hold the oil lines to the head are not identical at all.  Well not on my bike anyway.  One has a large feed hole in its side and the other has a small feed hole. Now I assume they were in their correct place when I removed them but I failed to look at them to see which rocker they each were for.  Can anyone out there save me?  Where do they go???  HELP

[Roy]

The one with the larger hole would go into the exhaust side ,👍 Roy

[chapmast]

I would also check the drain banjo bolt. If you have fitted one with the small hole then you'll be feeding in more oil than can drain out.

[neil1964]

The one with the larger hole would go into the exhaust side ,👍 Roy

Exactly!

[Bigsingle]

I think you'll have to remove the primary cover,  if it has a small one down there , the top rocker holes are approx 1.1mm , I've had to make my exhaust rocker feed 1.7 and clocked the shaft,  so that during the ex opening it dripples oil to the guide and spring , I've also got a bit of 1.25 copper wire in my return discharge hole in the oil tank to get a little more oil to the head , so far so good .

[neil1964]

The B31 feed comes off the main oil return (a banjo on the tank). The pipe splits to banjos on the end of each rocker shafts (both 65-1161
The pipe from the back of the head that drains excess oil from the inlet rocker chamber (not a feed). The rest of the oil drains via the pushrod tunnel.
B31/3 usually have same banjo screw (65-317).
Gold stars have the larger feed screw on exhaust (65-318- presumably for cooling) and smaller on inlet (65-317).
So if you have odd one's the larger diameter feed should go on exhaust.

[Derek996]

Neil, the pipe from the back of the head drains oil from both the inlet and exhaust rocker chambers. There is an oil galley from the bottom of each running to the horizontal galley with the banjo and pipe at the rear draining to the crankcase. The vertical drains are plugged with a screwed in plug at the bottom end. You can see the inlet one in the pic below. I had a hellish trouble with my B32 chucking loads of oil down the exhaust. I eventually found that the vertical drain from the exhaust rocker chamber was blocked with carbonised oil. 

[Calum]

I had a similar issue on my B31 - the upper drain banjo bolt was a small hole feed bolt and so the head would flood with oil and it would often smoke badly at lights etc after a decent run. Both feed banjos were correct, as was the lower drain banjo so my 'odd' bolt must have come from another engine altogether. I drilled it out to match the other drain banjo and all has been good since.

I suspect in your case you have accidentally swapped the drain banjo for one of the feed ones, which both increases the delivery and reduces the ability to drain at the same time.

[neil1964]

I had a similar issue on my B31 - the upper drain banjo bolt was a small hole feed bolt and so the head would flood with oil and it would often smoke badly at lights etc after a decent run. Both feed banjos were correct, as was the lower drain banjo so my 'odd' bolt must have come from another engine altogether. I drilled it out to match the other drain banjo and all has been good since.

I suspect in your case you have accidentally swapped the drain banjo for one of the feed ones, which both increases the delivery and reduces the ability to drain at the same time.

Sounds feasible (and with re-reading it is probably what @Bigsingle was trying to say about checking the size of the banjo holes on the crankcase behind the chaincase)?

[Calum]

I had a similar issue on my B31 - the upper drain banjo bolt was a small hole feed bolt and so the head would flood with oil and it would often smoke badly at lights etc after a decent run. Both feed banjos were correct, as was the lower drain banjo so my 'odd' bolt must have come from another engine altogether. I drilled it out to match the other drain banjo and all has been good since.

I suspect in your case you have accidentally swapped the drain banjo for one of the feed ones, which both increases the delivery and reduces the ability to drain at the same time.

Sounds feasible (and with re-reading it is probably what @Bigsingle was trying to say about checking the size of the banjo holes on the crankcase behind the chaincase)?

Yes, worth a check. Although, given that the bottom one (behind primary) has probably not been disturbed (not needed if he was just removing the head?), I would bet it is the correct one. My guess is the banjos on the head have been removed and put into a tray together, and mixed up upon refitting...

I did remove my lower drain banjo to make sure it was correct, but once removed I shortened the bolt slightly to facilitate future removal without disturbing the primary case (there is still more than adequate thread engagement).