my friend has a 1959 650 flash,what is the correct procedure for timing when refitting the mag, he has several books but they all give slightly different measurements for piston before TDC.
11/32" works well. What compression ratio is it? Manual or auto advance? Not that either make a huge difference.
thanks for that, I will pass that on to him, it is auto advance but do'nt know compression ratio
11/32 is the full advance setting so its wedges in the auto-advance and 1 - 1 1/2 thou feeler in the points. As its auto advance err on the side of 5/16 as you can't wing it if it goes a bit too advanced as you can with the manual A/R.
I asked this question on the BSA A7/A10 forum and BritBike. One of the well respected and knowlegable members on there had spent some time with their bike on a Dyno. Using modern fuel, the best his bike produced was at 1/4" BTDC timing setting.
I used that setting (as limey rob states, put wedges in the bob weights to keep them open), and I used a Mag timing light from these guys Magneto Timing Light (https://www.themagnetoguys.co.uk/magneto-static-timing-light). Dead easy to set and the bike went lovely after that. The bike doesn't ping and when before it felt like the engine was being labored and didn't want to rev anywhere near as much as my 830cc A65 with A10 crank... It did after, now it feels like I can gear the bike up a tooth or two.
Its tricky which is why I think the OP was right to ask. Mine is timed at 11/32 but its manual A/R so I can pull it back a bit if it feels wrong. I use super unleaded in the bikes not so much for the octane but for the reduced ethanol. Unleaded does burn fast so I can see the logic of 1/4" but it does depend on the CR. Mine's is 9:1.