Hi all - new member here with a recently acquired 71 A65T. My plan is to rebuild the engine over the winter and to that end I have tried to remove the head and barrel while in the frame, in the hope of making the engine removal process slightly easier/lighter.
However, I cannot lift the head clear of the barrel studs without it snagging on the top tube. Even with the rear rocker cover stud and oil feed pipe removed, there does not seem to be enough clearance to lift the head clear. All the rocker gear and pushrods have already been removed, all that is left is the casting itself.
Am I missing something obvious, or can the head not be removed in situ on these frames? Any tips or tricks gratefully received!
thanks in advance :)
I had a 1971 OIF A65L And I remember taking the head off in the frame, then the barrels. But you have reminded me that there was a trick to it. I have a copy the original factory workshop manual for 1971 and head removal is on page B5. It gets one paragraph that in summary says; disconnect the oil pipe, undo the 4 bolts under the rockers, then the centre bolt then the 4 nuts. Then tap under the exhaust port to free, then lift off. It seems you have done all that.
You may have to double nut the 4 studs, then undo them so you can slide the head across. I have a feeling this is what I had to do.
I was having a clear out last week and found a UNF ring that I had ground very thin. I have a feeling this was for the barrel nuts. I had my OIF A65 for about 20 years and really liked it but it was clear that BSA were in a rush to get them out the factory and its things like this that are the result.
Everything is loose and ready to come off, including the barrel nuts. I suspect there are probably clearance issues in lifting the barrel/head studs with the head - not sure there's enough room to double nut them with the head in place, and also not sure there's enough room above the studs to lift them clear of the cases even if there was.
At this rate, I may end up just removing the whole thing in one go, but I'd probably need help for that.
I removed lol the head of a 1971 Lightning a few years ago. Had to remove the studs. Did not keep the bike.
I seem to recall they are 3/8 UNF, check that but you should be able to get thin / half nuts which will give you room to double nut then unwind the studs. I don't recall them being tight.
Quote from: limeyrob on 22 Sep, 2026, 19:27 I seem to recall they are 3/8 UNF, check that but you should be able to get thin / half nuts which will give you room to double nut then unwind the studs. I don't recall them being tight.
Thanks I'll take a look. I guess my concern would then move to whether there was enough room for the head and barrel together to clear the pistons..?
It is a PITA job but can be done. I recently had the head off my 72 Thunderbolt. Did all that you have done so far. Then double nutted all studs to get the unscrewed. The 2 rear studs won't lift clear of the frame so I pulled them up clear of the barrels and zip tied them up. Then standing on the right side of the bike, lift head up and spin it 90 degrees so exhaust ports face you. Should then come out with a bit of wriggling about.
Tounge must also be poking out at least 20mm to the left. A supply of expletives is also recommended.....
The barrel does come up off the pistons but I seem to remember you have to tilt it forwards. Fine when you are taking it apart but tricky when it time to reassemble.
I re-ringed mine and swapped pistons too so I know its possible but I do recall it being tricky.
Looking at the barrel studs, they're long enough to leave about 4.7mm of thread proud of the nut (maybe closer to 5mm when torqued down). Wondering if removing this amount would give me the clearance needed. This would obviously need to be done out of the bike, but might be useful for re-fitting and any future head removal work. Thoughts welcome..
Ok - by way of an update - the head is now off. The one thing I hadn't tried turned out to be the answer. Namely, removing the forward rocker cover stud (I had previously only removed the rear stud, as this seemed to be the problematic one).
In other words, removing both rocker cover studs gives you the angles you need to manoeuvre the head off the barrel.
I'm now faced with removing a barrel that has been in place since 1971. So if anyone has a method that doesn't involve bending the fins, I'm all ears.. ;)
Funny how things come back, I now recall that rocker cover stud got unscrewed so many times the thread wore ;D
Could you use the studs to fit up some sort of clamp over the top tube and wind it clear of the crankcase studs, should be easier once that first bits done.
Thread a slide hammer into the stud holes to pull up on the cylinder. Check the thread first, should be UNF but if an early cylinder it could be BSF British Standard Fine. The cam followers will drop out if they do not have the circlips installed. You should keep them with the lobe they ran on and the same orientation.
Thanks for the replies. Managed to finally break the base gasket seal on the barrel by refitting the head, nipping up the four outer nuts and then tapping sharply underneath the intake stub with a rubber mallet.
Onwards and upwards - or in this case, inwards.. ;)