Further to Adrian's post re TDC in No 1. put your thumb over No 1 plug hole until you feel max compression then the piston is at TDC and in firing stroke.

Also the magneto distributor revolves in a contra direction to the vernier drive, check this when getting the firing order.

If the spark is happening at the correct plug at the correct time it will fire if you squirt some Easy Start into the carb inlet. If this occurs you can then concentrate on getting petrol from the carb to the cylinders.

Mike what compression readings do you have? Are the valves opening or have they stuck open due to lack of use? As mentioned earlier try easy start ,horrible stuff but does have it's uses, you should at least get a kick or blow back. Keep a fire extinguisher handy.This would if nothing else rule out ignition failure under compression.How much fuel in the tank? could be low flow if level low.

Location: Piddle Valley

Apologies if I have misread or ignored something elsewhere - but have you confirmed that you are getting a spark with the magneto installed, or merely that a spark is produced when rotated by hand?

If the latter, then consider whether there is a fault in the wiring to the switch panel.

Peter

I had a similar problem with the Cup. When I started it for the first few times it fired up immediately. I then left it for a couple of years while I sorted out all the wiring and various other tasks. The last job on that particular list was to take it round to my local friendly tyre & exhaust place to get the toe-in checked. No problem, I thought, just start it up and off we go.

Would it start? No way. Fresh fuel, checked timing, sparks, towed up & down the road by No.1 son at frightening speeds, but other than the odd splutter, nothing. Nix. Timetable ruined, deadline for a rally gone, so turned to all the jobs that needed doing instead of building a Special.

Fast forward another year or two, more jobs completed (including a frustrating and lengthy hunt for fading oil pressure) and time to start it up again. Same result as before, but didn't bother to faff about with the mag this time. Plugs out, covered in oil/petrol. Cleaned them, still nothing. Why not try another set of plugs? Nothing to lose. Original plugs were a set of new KLG M80s that I had bought back in the 1970s. Tried a set of new Champion D16s. Instant result - yay!!