We just took delivery of a new S40. Very impressed lots of character, I read elsewhere that it fires on both the power and exhaust - is that true?  If so why?  It might explain the occasional pop in he exhaust on overrun...
Geoff

It does it for the sake of simplicity...
A low revving single has plenty of spark to spare, so why make things complicated?...
Just make it fire on every cycle...

There can be no performance gains from additional spark on this ol' plodder...
...

IF you decide you gotta have one, it's been done. Kinda pointless,really..
It's a torque monster, no one has ruined one because they didn't have a tach. I know I rassled with the idea, Ohh Boy, I NEED a tach on this thing..
I watched people who did it, what they bought,how they solved all the problems of mounting, and, at the end of the day, I couldn't see how I REALLY would benefit from having a gizmo tell me how fast the motor is turning over. The idle speed is the critical one,and I felt comfortable with that. I was either thrashing it, ripping thru the gears, or cruising around easy,, and I don't need a tach for those...

Oh, you put a tach on it,, neato..
I decided I didn't need that,,

Know the motives of the Heart.

Firing on every revolution is very common these days.  In the old days they had one coil supplying electric energy to all the cylinders, and a distributor decided which cylinder it should go to...and when.  Now we avoid the complexity of a distributor and have a separate coil for each cylinder, and it has plenty of power to spark every revolution.  It doesn't do anything weird....as the extra spark occurs during the beginning of the exhaust stroke, and the fuel is all burned up at that point.

I think the big reason is simplicity. With a wasted fire system, you stick a pickup down where the stator already is.  There is already a crank exit from the block with bearings and seals, a spinning rotor onto which a small magnet can be placed, and a wiring exit.  No need to make another exit with bearings and seals for the cam.

It works just as well and cuts out a lot of costly machining work.
You can run a single with one coil and one pickup.
You can run a twin or a 4 with 2 coils and 2 pickups.

Old bikes with points used to fire off of the cam which meant all that extra machining and a spark advance system and the cam to operate the points. 2 sets at 90º apart running off the cam run a twin. 2 sets of points at 180º run a 4.

These days you can get by with one pickup on the crank, a small computer to calculate piston position and fire the coils when necessary for any number of cylinders.

I don't miss the distributor cap and rotor on my car (or the points).  I remember those being regular maintenance items, and sometimes the reason your car wouldn't start when the distributor cap became cracked or got really wet.

We have become pretty used to the fuel injection and electronic ignition in our cars these days - but when I started driving it was hand chokes, carbs, points and condenser....and on my first car a 6 volt electrical system.  Thankfully we had a steep bank up to the barn and I would park my 1950 Plymouth on that hill in the winter....so I could coast down the hill, out the driveway and out to the steep hill on the road - where I could get my car started by coasting down the road.  After my 22 year old car sat out all night in the cold the 6 volt system would never start my car in the morning....even with a good battery.

I can also remember folks putting heat lamps in with the engine, and a blanket over the hood to keep the engine warm enough to start in the morning.

Justin,

What you jest about was part of my early life.

In Ireland the galvanized tub was put on the wood stove early Saturday morning to heat up the water for the Family Bath night. When we moved to the USA, for my father to work at the Marietta Depot, the outhouse was further from the house and there was a boardwalk to get to it. It was an upgrade because we had the Montgomery Ward catalog as an amenity.

The American galvanized tub was big enough for both my brother and I to get bathed together, and we had the clean water.

I cannot remember how they got that big tub from the wood stove to the kitchen floor.

Life was good.

Kenny G