MD no spark

IAtractorKid · May 18, 2012

Hey guys! Went to start the MD today and it was a no go. No spark out of the coil or any of the plugs. It has a magneto ignition and i have never worked on a magneto so could use some guidance! Started and ran great last weekend, sat in the shop all week and then nothing today. Ideas???

Bob M · May 18, 2012

Is the magneto making a loud "snap" every 1/2 revolution of the crank? If not the mag impulse coupling is not working. You'll need to remove the mag and clean/oil the impulse.

If the impulse is snapping, next then disconnect the wire running from the manifold switch to the mag. Could be the manifold shorting switch has stuck closed and is preventing the magneto from sparking.

If that doesn't do it, remove the mag cap and clean/re-gap the breaker points (set the points to 0.013)

Still no spark? Time to get in touch with a reputable magneto repair shop!

SadFarmall · May 18, 2012

First thing to do with an H4 magneto is to remove the coil cover (four cheese head screws) and check the contact between the coil and the strip, which connects the high tension wire, leading the centre of the distributor cap. There is often a bit of corrosion or copper sulphate build-up here, which kills the spark. If this does not work, then you need to start pulling the magneto apart. It is highly desirable to have an Owner's Manual and/or Workshop Manual to help you do this. The magnetos are not difficult to work on, but without an exploded diagram and instructions, it is easy to set the magneto timing incorrectly.
SadFarmall

jim warehime · May 18, 2012

You definitely want to check that wire from the mag to manifold I would do that before checking anything else. Might need new insulators which is a cheap fix had. One go bad on my MD. Jim

Brownie 450 · May 19, 2012

Easiest thing to check is to pull the dist cap & check that the spring-loaded carbon button isn't worn down to the nub/ missing. Then check for spark from the mag "output" using a new wire to ground. Last thing to do is take the mag apart.

IAtractorKid · May 19, 2012

I dont hear a loud snap but over the tractor turning over i dont know if i would hear it anyway. Plug wires were replaced yoday along with the wire from the manifold to the mag. No spark coming from the coil before or after the new wire. So i need to pull the mag apart???

sflem849 · May 20, 2012

I don't hear my mag snap when I am using the starter. I do hear it if it still spins after I let off the starter. You will also hear it if you spin the engine by hand.

MD no spark

IAtractorKid

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Bob M

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SadFarmall

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jim warehime

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Brownie 450

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IAtractorKid

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sflem849

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