Bendix magneto internal timming

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Bendix magneto internal timming

Postby Madwrench » Sun Jun 10, 2018 12:00 am

I recently purchased my first airboat project, its all there but I’m trying get it running before I bail off too deep into it. It has an 0-435 on it that so far seems to be mechanically sound. Had no spark, I filed the points in both mags (bendix) and now have spark then found that both mags where a mile out of time. I pulled both mags apart to clean them and re set the internal timming. Neither mag has an impulse mechanism on it, at least they don’t look like what I’ve seen in the information that I’ve found, they look more like a balancer of some sort and do not appear to have any spring loaded internal movement. Both mags are clockwise rotation. Now, my question is that there is information embossed onto the distributor gear “ccw, ccw with impulse, cw, cw with inpulse” left side has the red mark on the tooth for “cw with inpulse” Even though it do not have an impulse deal. And the right one has the red alignment mark on the “ccw” mark even though it rotates clockwise. I can’t find any online information on these details. There’s as much as 4 teeth difference which I know will affect the rotor timming. Any info, or a link with this info would be appreciated. Also another thing I’ve found on this engine is that the engine plate calls for ignition timming to be set at 15deg. All the post I’ve read about timming have been 20-25deg and the flywheel only has 0, 20, 25deg. Marked. Should I still stick with 15deg? If so I guess I’ll have get some sort of degree wheel and make a new mark.

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Re: Bendix magneto internal timming

Postby Slidin Gator » Sun Jun 10, 2018 12:37 am

Your post started with Bendix, are these series 20's or other? I am attaching information on timing the series 20 in case it helps you. The most confusing thing is that the distributor rotates the opposite direction from the engine and aviation rotation direction is the opposite of airboat direction. The manuals are muddy at best on this, but the CW and CCW marks refer to the direction of rotation of the distributor, not the engine. I put the attached together just to explain it to myself the next time I need it!
Bendix 20 Mag Internal Timing.pdf
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Re: Bendix magneto internal timming

Postby krazymatt » Sun Jun 10, 2018 1:39 am

When I set mine (20 series bendix mags on o435-1) GMAC76 helped me. He advised set both mags the same - "cc normal" and install them at 15 degrees before tdc. If you have a 149 tooth lycoming flywheel each tooth is equal to about 2.5 degrees. Bring #1 cylinder to tdc then back it up 6 teeth. You may want to go a little past then bring it back to the 6th tooth to take the gear lash out. You will need a buzz box to time them right. Try it with the setup you have now and if it's hard to start especially hot you may want to add impulse coupling to one of the mags.

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Re: Bendix magneto internal timming

Postby mojoe » Sun Jun 10, 2018 7:08 am

Slidin Gator wrote:The manuals are muddy at best on this, but the CW and CCW marks refer to the direction of rotation of the distributor, not the engine. I put the attached together just to explain it to myself the next time I need it!

Very nice, thanks for putting that together and posting it.
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Re: Bendix magneto internal timming

Postby GMAC 76 » Sun Jun 10, 2018 10:02 am

X2....KRAZYMATT......both mags on the 435 are left hand rotation.....I have never seen a dist gear marked "with impulse" unless these are the old old lunch box bendix mags ...most lyc engines time at 25 btdc but the old 435 times at 15

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