Hi Tony..Taking off the barrel is fairly straight forward. Points to note are that there are 5 base nuts..the fifth one being inside the tappet chest between the tappets.
Also you have to remove the valve lifter assembly from the barrel before lifting it..otherwise you will damage the flange on the exhaust tappet that the lifter peg operates on. Disconnect the lifter cable from the arm and then unscrew the whole lifter assembly from the barrel. Strangely, the size of the hexagon on the lifter bush (that is screwed into the barrel) is 20mm A/F...so you will need a spanner of that size.
Make sure you have all the necessary gaskets to hand..cylinder base, tappet cover and head gasket.
Also you will get a chance to inspect the tappet heads for wear..they should be completely flat where they contact the valve stems. If the engine has done a few miles expect them to be worn and needing replacement.
With the barrel off I would also take out both valves to check the condition of the valve seats and faces..at the very least it is likely the exhaust side will need lapping in again.
Also check cylinder bore condition and ring gaps..again if it is a high mileage engine, but with a good bore, a new set of rings might be beneficial.
You will need piston ring compressors when it comes to refitting the barrel..and it is best to put two paralell bars or similar either side of the conrod and under the piston skirt to hold it square initially while you get the barrel over the rings.
As far as cleaning the barrel is concerned you won't achieve much doing it in place..most of it is not accessable...Wet Vapour blasting is the best method and will remove all paint/rust etc. leaving a perfectly clean finish in readiness for repainting.
However, if you use that method make an arrangement to pick up the barrel as soon as it is done..exposed cast iron developes surface rust very quickly!...Ian
email (option): ian@wright52.plus.com
One point I forgot to mention..With the barrel lifted clear of the crankcase..but before the rings come out of the barrel...put some clean rags around the conrod that block the crankcase 'mouth'. That way if there is a broken ring the bits won't fall into the crankcase as you lift the barrel off...Ian
email (option): ian@wright52.plus.com