Splitdorf NS2 timing

[pisten-bully]

My magneto fires late, if I advance the spark fully the rear cylinder stops firing (maybe starting halfway through the advancing stroke). I know it should spark at 7/32 (.2187) BTDC when fully advanced, but the points don't open until .185 BTDC on the front and at .169 on the rear.

Before I go to the hassle of opening up the motor timing case to check there, I'd like to verify that the fiber gear for the rotor and the steel gear for the breaker cam meet at the correct spot. I've located both timing marks for those gears, put a spot of white paint on them, but the point where they mesh is hidden.

How can I get a clear view of that meshing spot? Pull the rotor assembly? Or pull the breaker plate? Or both? Or neither?

And how do the rotor assembly or the breaker plate come off? I don't want to mess things up more than they already are and I can't find an answer! Thanks!

[pisten-bully]

...this is what I'm looking at, an NS2 with the points cover and distributor cap removed. The top u-shaped thingy up high with the pointer at the end holds the rotor (removed), and the bottom is the points breaker with the breaker cam in the middle:

image_53015.jpg

...and this is one way to test for when the points open, there's a 6V lantern battery in the circuit with a small light and two clips attached to the both points, I've got the front cylinder head removed so I can measure the BTDC:

IMG_2554.jpeg

[gharper]

In order to accurately check the proper meshing of the timing marks, simply remove the points assembly. Use a 5/16" deep socket and remove the two long studs on either side of the points assembly. Lift the plate out and check. Be sure to lube the plate where it rotates on the body and copper springs before reassembly. I'd go with a minimum of 3/8" BTDC, but 7/16" is fine too. You may need to advance the timing by a tooth. Also, playing with point gap will make a big difference on timing. I believe the Splitdorf book says .020" point gap but I've adjusted mine up to .024" to get my full 7/16" advance on my Excelsior and Chief.

In addition, check timing on BOTH cylinders, it will be different! There is a bit of fudge on the pin that locates the cam as well as the cam gear on the shaft. Both of those can be used to gain a bit of advance. Be sure when checking timing that all of the slack is out of the gear train. I use a big screwdriver in the slot for the cam retaining screw, gently holding reverse pressure on the train.

Also, the timing of the U shaped retaining clip that holds the rotor must point to the correct wire for each cylinder. When the points are opening on the short lobe, the rotor must point to the rear connection on the cap, with the wire going to the front cylinder. The large rear cam, is for the rear cylinder and when opening the points, the rotor must point to the front wire connection, which goes to the rear cylinder. Check that the rotor is contacting the brass wiper in the cap with the spark fully advanced, as well as fully retarded, for both cylinders. If the timing marks are off, or have been altered, it may be that the rotor brush is not making contact at full advance, or retard.

Keep in mind that in order for a magneto to produce the hottest spark, two things must happen simultaneously: The rotating pole must break the magnetic field at the exact same time that the points open. Easy on a fixed timing mag, but your mag has adjustable timing, so rotating the points will change this ratio. The hottest spark is in the middle of the points rotation. That means that full advance and full retard are actually weaker sparks. This usually isn't an issue if the magnet is fully charged, but can sometimes cause hard starting and a miss at very low speeds. One thing that can help here is to decrease the spark plug gap, so a weaker spark can actually make the jump at very low speeds, or starting. I set my plug gap at .015" and have had good luck all around. This may help with the missing on the rear cylinder.

Good Luck!

[tfburke3]

I don't think a test light or multimeter will accurately show point break on magneto..
I use an induction magneto timer or a timing light with flywheel marks made during assembly ,visible thru vent line hole while running.
Tom