Unison magneto troubleshooting

Unison Magneto Troubleshooting By Harry Fenton February 1999 Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12...


Be certain that the p-lead connection from the tool is not grounding on the magneto frame.

Always have the fiber washer installed when the timing tool alligator clip is attached to the p-lead. Many timing problems can be traced back to the clip simply by finding ground at the p-lead connection (Figure 9), which can result in a magneto that is stubborn to provide point opening indications.

If the batteries and connection are sound, snap the magneto through two or three times to burn off any contamination that might be present on the point faces. Be careful not to snap the magneto too many times without a sparkplug attached to receive the load, otherwise the magneto coil may be damaged. If the problem continues, connect the tool to another magneto to see if the problem follows the tool or is a condition limited to the magneto in question.

Once the magneto is installed on the engine and ready to be timed, connect the ground lead from the timing tool to the magneto being timed. If the ground lead is attached to the center of the engine, sometimes the ground path is too difficult for the timing tool circuit to complete.

Setting up E-gap
Setting up the internal timing of the Slick magneto is easy and accurate, as long as the correct procedures are used. Most problems related to internal timing are related to the improper use of the Slick timing tools.

For many years, the standard tool used to set-up the E-gap of the Slick magneto was the T-100 timing tool (Figure 10). The T-100 is a combination base and pressing tool used to disassemble and time the magneto.

The old method of timing Slick magnetos specified that the timing disc on the T-100 baseplate (Figure 11) be set up to a certain number of degrees appropriate the particular magneto model being timed. Once the base plate was set, the impulse end of the magneto was engaged into the slots on the reverse side of the timing disc. The frame of the magneto was then rotated until the left side of the frame contacted a stop pin in the base of the T-100 (Figure 12). This method positioned the rotor shaft into E-gap, and the contact points would then be adjusted to just break open.

It was an easy-to-use method, but somewhat inaccurate. The basic problem was that due to the stackup of tolerances that could occur when referencing from the impulse end of the magneto up to the contact points, achieving the proper e-gap setting sometimes proved difficult. Subsequently, a more accurate method was devised. Also, mechanics would sometimes set up the disc to a degree number not applicable to the magneto that was being serviced. For example, the T-100 timing method was applicable to the 4200/6200 series impulse magnetos only, consequently, there are no approved procedures provided by Slick to use the T-100 to set up the E-gap on 4300/6300 series impulse coupled magnetos.

During the late '80s the rotor shaft for the Slick magneto was changed to incorporate slots to accommodate the Slick T-150 E-gap gauge (Figure 13). The T-150 E-gap gauge inserts into the rotor shaft and provides for extremely accurate positioning of the rotor shaft.

The notched end of the E-gap gauge inserts into a slot in the rotor appropriate to the magneto rotation. With the T-150 inserted, the rotor shaft is turned in the direction indicated by the arrow cast into the rotor head next to the slot for the T-150 (Figure 14). When the tool contacts the frame (Figure 15), the rotor is set in the E-gap position and the contact points are then adjusted to just break open.

After the E-gap has been set, remove the tool, turn the rotor shaft to position the cam to the highest point of lift, and use a feeler gauge to check the point gap opening. The point gap range is .008" to .0012".

Never set the contact points by just using a feeler gauge! Setting the contact points to a particular gap setting does not accurately position the rotor shaft to optimize E-gap. Always use the T-150 tool to set E-gap first, and then use the point gap measurement to determine the go/no go condition of the contact points. If the point gap falls outside of the specified range, then the point and cam combination are worn beyond limits or the internal e-gap set up was done incorrectly.

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