Hi all,
I am the point where I need to buy carbs. Machine 1, is Oct 1968, 9:1 pistons with a twin carb head. The other is Aug/Sept 1968 single carb head with 9:1 pistons (Thanks JulianJ for dating). Both heads have 1.598 inlet and 1.410 exhaust valve diameters.
I have looked at the manuals and services sheets and I not sure which would be the best carbs to buy, jets and settings I should adopt as I am sure I haven't got all the information. I am also aware that as time went on BSA improved fuel delivery.
Any spark plug advice would aslo be appreciated.
Best wishes.....
Data listed for your 1968+ engines with those valve sizes and compression ratio are:
Lightning
930/34 + 930/35
main: 180
Needle jet: 106
slide: 3.0 cutaway
pilot: 20
Thunderbolt
928/6
main: 230
Needle jet: 106
slide: 3.5 cutaway
pilot: 20
Thanks again Arthur.
Best wishes...