hi Alice,
several things to check,,electrical to start with
#1 take the lhs cover off, check the pick up wires where they move with the base plate, take them out of the holder clamp and the rubber grommet in the motor, and pull all 4 of them them firmly, one at a time, one of them will more than likely stretch a lot further than the rest,, if so you have a simple broken wire, resolder and bob's your uncle, make sure when repositioning that the same amount of movement exists as before you disturbed them
#2 check, or get some one to check the resistance of coils,, Primary and Secondary curcuits, more than likely a good auto sparky
#3 lift the cover on the TCI box,, check the curcuitry board,, the solders immediately at the base of the 2 big plugs,, looking for differing surfaces to the rest of the board,,again a good auto sparky will be able to test and tell,,,,,,,,DO NOT spend $400 on another 4RO box-- IF-- you can find a new one-- IF-- it's cactus,,-------far cheaper alternatives exist
#4 while your checking resistances and such,,, check the plug caps as well,, some thing simple, BUT the simple things are usually what get you on these bikes
check these first,, am betting on a broken pick up wire,, then go down the list,,
will wait to hear back, how you get on