Hello. Ref my early C25 engine No C25-317. I've owned the bike for nearly 50 years, but have only recently reactivated it.
The workshop manual and the excellent RR book show that adjustment of valve clearance is achieved by turning the eccentric rocker spindles outwards. Later engines from engine No C25-2050 onwards had revised spindles and rockers and adjustment was achieved by rotation the spindles inwards.
However, on my bike the spindles have to be turned inwards to set the valve clearances when according to the above they should be turned outwards. The engine starts, runs and idles nicely.
A BSA Service sheet from July 1967 shows the modified rocker arrangements and states that the new arrangement is interchangeable as a complete rocker box assembly, but individual components are not.
Would anyone know if the later rocker spindles would in fact fit into my earlier rocker box. The rocker box does seem to be original as it includes the internal rib that the Service Sheet shows as being removed for the later arrangement. If so and a previous owner had done this it might explain why the valve setting procedure is apparently reversed.
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Interesting question. From memory the rocker spindles are the same for all years, including the position of the flat relative to the eccentric portion. So adjusting valve clearance with the flats facing towards or apart would have an effect on the rocker position relative to the valve. As far as I know the spindle hole centres weren't changed when the rockerbox changed. Whether the rockers changed in terms of their geometry I don't know. In case there were any changes made to rockerbox spindle position or rocker geometry I be tempted to stick with BSA's instructions for setting your valve clearances and if correct clearance can't be obtained I'd investigate why.
Is that because you can't achieve enough clearance or because you have too much clearance which can't be adjusted out?
From my personal experience with these eccentric spindles , I would view through inspection cap to examine exactly where the rocker arm is over the top valve spring coller and if need be adjustso the arm moves away from coller , I have worked on many engines where the arm has hit the coller ,the collets have jumped out and you can guess the rest ,Roy
Thanks for the replies.
The reason for enquiring is that if I try to adjust as per the manual the inlet rocker arm fouls the top valve collar. The exhaust spindle can actually be just turned fractionally in the correct direction to achieve a clearance and the rocker doesn't foul the valve collar, although to my eye the rocker geometry looks better when the spindle is turned the other way.
According to the Draganfly website, there are different part numbers for the spindles and rockers for the later engines.
I'll get the rocker box off and investigate. Thanks again