Triumph Repair: ignition, air gap, rule of thumb

Question
Have a1975 tr7 twin stroms, plugs were replaced but will not start the spark on the plugs appears orange in color when testing.

Answer
Hi Brian,
An orange or yellow spark is a sign of a weak spark. (not viewed in the sun light) If you don't have access to a scope to test the voltage of the spark you can make a few rough tests of your own. You need an insulated pair of pliers or anything insulated to hold a plug wire close to the head and spin the engine and note how far you can jump a spark. Most sparks are ok if they will jump 3/8 inch.
If you still have the amplifier on the side of the distributor (Opus / Lucas system) that is most likely your problem as most of those amps failed before they got out of warranty.
Check the resistance of the plug wires and check the air gap in the distributor (.015") As I remember the wire was 25K ohms per foot of length was a rule of thumb.
Howard