O 200 S4 LN 21 Magnetos overhaul

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N500BC

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Nov 30, 2015
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Bogotá Colombia , South America
I have a Continental O200 with the above mentioned magnetos. It was running fine. Now I do not seem to be able to get ignition. Engine turns but does not ignite the mixture... it seems! I replaced the harness and the REM 40 spark plugs. I have a key ignition switch.I hear the impulse coupler click every time I turn the prop. Does anyone know of a good shop in Florida that might be able to overhaul these mags? Is it a job that can be done "at home"? Any one know of manuals or books that can guide through the process of repair/overhaul?
Please help! I want to get back in the air (safely!)
 

TFF

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Apr 28, 2010
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Memphis, TN
The points need to be adjusted every couple of hundred hours, not timing bumped to compensate for timing loss. You can do this without much major disassembly.

They are very easy to work on if you have the confidence to try. Once you do it’s a, what’s all the excitement about you item. Age, time, are important. If it needs a block, you might have a shop do it just on cost to work ratio. Even then. They are put together upside down.

If you are going to send it away, you might as well take it apart to see if you can do it. The bottom case and drive gear are the last to go on. Just don’t put your fingers in the block.
 

Dan Thomas

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Sep 17, 2008
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6,617
You probably have the harness crossed up. There should be identifying stamps on the harness's sparkplug nuts: T1, B1, T2, B2, etc. T1 goes to the top plug of # 1 cylinder, B2 goes to the bottom plug of #2, and so on. On the O-200, the #1 cylinder is on the passenger side at the aft end of the engine, and #3 is in front of it. #2 is the rear cylinder on the pilot's side and #4 is in front of it.

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proppastie

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NJ
I once pulled on an engine 2 days because I confused the firing order of the mags with the firing order of the engine. It would pop but not run.
 

TFF

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Apr 28, 2010
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I have a friend who mixed wires right before he had a sale. At least twice. He is one who you would not expect to make that mistake. I have made it on my plane too. Rookie.
 
Joined
Feb 17, 2014
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Grantham, NH
Pull the leads off the plugs, turn the mag switch to both, one at a time, hold a lead about 1/8” from a metal part of the engine, where it’s a bit dark behind it so you can readily see it spark, pull the prop around and watch for a spark when the impulse clacks. It’s easier if you get a friend to hold the lead inside his mouth: NO! I mean pull the prop through for you...it may take multiple clacks of the impulse until you get a spark, as the mags work their way through the firing order. If you get no sparks anywhere, remove the p leads from the mags and try again. If you get sparky-sparky now, remove the mag switch from the panel and check it with a VOHM meter, because they can go south, too.
 

Dan Thomas

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Sep 17, 2008
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6,617
Another way to mess up is to rotate the prop to the timing mark on #1 for mag installation without making sure you're on #1's compression stroke. It puts every spark 360° out of phase, firing at the top of the exhaust stroke.
 
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