Points to coil wire ?

I cant get my 74 commando to start.I have spark.My ? is do the points in the front go to left or rt. side coil,blk/w wire to which coil.I found under the tank the bullets for blk/w and blk/y were togeather instead of blk/w to blk/w,blk/y to blk/y,the wireing dia. is not much help.I get a pop out of the right pipe,any help is much welcomed.Pete

Easy enough just switch the wires at the points and see if it cures the problem.

Instead of using a distributor with a cap and rotor, Norton as well as BSA, Triumph, etc. used a complete and separate ignition system for each spark plug. However, the points use a common cam for opening and closing the points. The points cam or automatic advance unit (AAU) can be installed in any position so that either set of points could be used for the left hand or right hand cylinder on your motorcycle. It sounds to me that someone installed the AAU 180 degrees out of phase so that the spark plugs are firing on the exhaust stroke instead of the compression stroke. So instead of removing the AAU, and repositioning it, he simply swapped the black and yellow & black and white points wire. There is nothing wrong with doing that it is just a quick and easy way of dealing with an oops.

If you are not sure as to what set of points is firing for which cylinder, remove both spark plugs and put your finger on the right hand spark plug hole, slowly turn the engine over using the kick starter until you feel compression building within that cylinder. Look at the points cam and determine what set of points is getting ready to open. Turn the ignition switch on, put a spark plug in the right hand spark plug wire and physically open and close the set of points that you determined were getting ready to open using your finger or some kind of small screwdriver. You should see a spark in the right hand spark plug. If not, see if it sparks on the other side and if it does your points wires are backwards.

Good luck, I hope this helps. Peter Joe

illf8ed said:

Easy enough just switch the wires at the points and see if it cures the problem.

Click to expand...

That did the trick on my first Commando, a '69 I bought non running waaay back in the '70's...did a lot of kicking with nothing but pops, my father gave the same advice and it fired right up, the PO had reversed the wires at the coils at some pont

Thanks I found an old post with the info,left points left coil,swetched the wires and now it will fire.It starts on the tickler and stalls.I think the gas tank is still surrendering rust.I`ll try to clean the pilot jet and the tank again.1 step foward...

According to my workshop manual, "Normally the Left contact breaker set in the distributer (to which a yellow and black wire is attached) is used for ignition on the Drive side cylinder."