Ignition Timing Conundrum
Posted: Mon Mar 20, 2017 4:28 pm
Hi All
I'm after advice again please. My 1956 AJS 16MS (Now 500cc) is fitted with a Lucas N1-4 magneto in place of the SR1 which would have been fitted in 1956.
I have finally sorted out the poor starting problem of the last year or so when I realised that the spark plug gap suggested for the N1-4 is 0.015" to 0.18". I had set the various plugs that I had tried to 0.020 to 0.22" as shown in the handbook for the 1956 bike. It now starts as it should do.
I have recently carried out a top end rebuild and the original flat topped +0.040" wire wound piston has now been replaced by a new +0.060" piston from the club spares scheme. This piston has a domed top, so I presume that the compression ratio is now higher that it was.
My experience with the differing spark plug gaps and the potentially raised compression ratio now leaves me wondering what I should do about the ignition timing. The 1953 manual for the bikes fitted with the N1-4 shows that the timing should be set at 7/16" BTDC fully advanced. I have set the timing on my bike to 1/2" BTDC fully advanced as shown for the 1956 bikes.
I'm relatively new to these bikes, so any advice would be much appreciated.
I'm after advice again please. My 1956 AJS 16MS (Now 500cc) is fitted with a Lucas N1-4 magneto in place of the SR1 which would have been fitted in 1956.
I have finally sorted out the poor starting problem of the last year or so when I realised that the spark plug gap suggested for the N1-4 is 0.015" to 0.18". I had set the various plugs that I had tried to 0.020 to 0.22" as shown in the handbook for the 1956 bike. It now starts as it should do.
I have recently carried out a top end rebuild and the original flat topped +0.040" wire wound piston has now been replaced by a new +0.060" piston from the club spares scheme. This piston has a domed top, so I presume that the compression ratio is now higher that it was.
My experience with the differing spark plug gaps and the potentially raised compression ratio now leaves me wondering what I should do about the ignition timing. The 1953 manual for the bikes fitted with the N1-4 shows that the timing should be set at 7/16" BTDC fully advanced. I have set the timing on my bike to 1/2" BTDC fully advanced as shown for the 1956 bikes.
I'm relatively new to these bikes, so any advice would be much appreciated.