6 hours.<\/p>\n
One of the day’s tasks was to replace the magneto gasket we tore with a new one. \u00a0 This necessitated removing the right magneto, the one that was cranky about timing. \u00a0 This is also the mag that has the hinky contact spring on one of the harness wires. \u00a0I figured what the hell, I’ll make sure both are timed, so I’ll pull both, put new gaskets on both, and set the timing again. \u00a0 Big mistake. \u00a0 Timing mags with two people sucks, as you might have gathered from an earlier post. \u00a0 Doing it on your own sucks too, and then some. \u00a0 Yesterday it was hot and windy at OXR, so the hangar was warm and the doors were rattling and making freakish noises every couple of minutes.<\/p>\n
There are various sources of knowledge as to how to time mags, but the general idea is that you turn the engine over until the crankshaft is at 25 degrees before top dead center. \u00a0 Then you zero the mag position by sticking a pin in the timing hole in the back of the magneto where it will sink into another timing hole on the gear inside, thus locking the thing into the position where the points are open. \u00a0Then you stick the mags back on your timed engine.<\/p>\n
A number of factors are at work here. \u00a0 There’s the impulse couplers, there’s the slop in the mags even with the timing pin inserted, there’s gear lash in the engine itself, and there’s the ambiguity of where 25 degrees BTDC actually is. \u00a0 Near as I could figure out, there’s a little lump in the rotation of the mag gearshaft where the points open. \u00a0 This is no great mystery. \u00a0 A cam inside opens and closes the points to make a spark. \u00a0That fires the spark plugs. \u00a0This is no different from your common Briggs and Stratton-powered suburban lawnmower.<\/p>\n
But the magnetos are buried amongst wiring, hoses, and engine mount tubes, and getting them back on can be extremely frustrating. \u00a0The mag gasket is a little wider than the magneto housing, so it’s really easy to dislodge it. \u00a0 The engine gears of the mags are also wet with engine oil, so they’re slippery. \u00a0 It’s also of primary, critical importance that nothing falls down the open mag hole into the accessory case. \u00a0 If that happens, game over. \u00a0If that happens, you better hope whatever fell, like a nut or a washer, falls all the way through into the oil sump where it gets stuck to a magnetic plug — if you have one. \u00a0The obstacles in the way make it easier, but not by much, to insert the timing pin into the housing with the mags more or less in place, but supporting them, spinning the gear, and inserting the pin is one of the more frustrating solo tasks there are. \u00a0The trick is to get both mags installed so they’re within just a few degrees of each other, because there’s only about 70 degrees of twist available to bring them into line. \u00a0 \u00a0If they’re too far off, they’ll never sync up.<\/p>\n
The next part is relatively easy, assuming the first part goes OK. \u00a0 This is where the buzz box comes in. This thing has two lights on it, and you connect the leads to the P-lead connections on the mags. \u00a0When the points are closed, the lights are on. \u00a0When the points are open, the lights are off. \u00a0 Or vice versa. \u00a0 Can’t remember. \u00a0 The point is, the status of those lights is supposed to change when the engine turns through the specified timing mark on the flywheel. \u00a0 Both mags are supposed to change at the same time. \u00a0 \u00a0There’s actually enough wiggle room with the timing pins in the magnetos to put the timing off by a whole gear tooth. \u00a0If it’s off in opposite directions on each mag, there might not be enough range to bring them both back into line at the right point. \u00a0 \u00a0 But eventually, I got it. \u00a0 The trick is pulling the prop backwards a bit, then advancing to see the lights go. \u00a0 The prop has to be pulled backwards enough so that going forwards takes out the gear lash well before the points open, otherwise the adjustments are crap. \u00a0 But you don’t want to go so far back that you catch the impulse couplers again. \u00a0 \u00a0Maybe this isn’t the proper way to do it, but this worked for me. \u00a0Also of important note: pull the timing pin out of the magneto before cranking the engine around. \u00a0 If you don’t, best case is you’ll bend your timing pin like a wet noodle. \u00a0Worst case is you damage the innards of the mag.<\/p>\n
So I got them as close as I possibly could. \u00a0 \u00a0Then I put the shielded ground wires back on. \u00a0 For safety, the shielded wires go back on the P-lead and ground before the distributor caps go on, because until they’re on and grounded, the mag is hot, and if a spark is triggered, it could swing the prop and really ruin your day, especially if you or your stuff is in the prop arc. \u00a0 Imagine that. \u00a0The prop kicks and sends a blade into the tank of your air compressor or a nearby tool cart. \u00a0 Prop strike! \u00a0 Have fun tearing down that engine, sunshine.<\/p>\n
By the time this process was over, I was already well past my scheduled time to head back to Los Angeles. \u00a0 But if you’ll remember, this exercise was only part of the day’s activities. \u00a0 The other things I needed to attend to were the RPM sensor and the oil temperature probe. \u00a0 Earlier in the week, Matt at MGL responded to my email and said I needed to remove the ballast jumper on the RDAC and that I could delete the resistor between 12v power and sensor signal. \u00a0 I pulled the ballast jumper, then proceeded to push the ship out into the wind for a quick test. \u00a0 \u00a0Ron and Melody helped me push out and get pointed into the Santa Ana wind. \u00a0 With the wheels chocked, I fired it up, once again.<\/p>\n
![\"IMG_1556\"](\"http:\/\/stjohn.openbar.com\/airplane\/wp-content\/uploads\/2013\/10\/IMG_1556.jpg\")
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