John Deere M need coaching....

My JD M running rough, has new plugs, condenser, points, gaps set correct, fresh premium gas, unsure about coil? Tractor starts and runs, but has little power, spits/ sputters, sparks out of the exhaust?? Pulled plug wires off (one at time)when running and with both the spark is weak.. Unsure what coil does? Any ideas??
Thanks

Sounds like timing more. Of course those 2 cylinders you are missing makes it sound bad too. LOL

You didn't mention plug wires or timing. You need solid plug wires and the timing set with a light. SPARK should be in the center of the timing window at full throttle & if the dist is in good shape it will be close to TC/DC at low idle. It would probably be a good idea to check and clean all the wiring connections from the switch forward. If it's still 6 volts this is critical. Check the coil voltage. Less than 5 and there will be problems. Once you're positive the ignition side is in tip top shape you can move on to the carb, breather, and valve lash.

BTW - BAD condensors are common as dirt now a day's so it's never a bad idea to swap it out when one is running rough even if it's new.

Does your John Deere have a coil? Or can it be a magneto unit? If you did a tune up and did a tne up in the magneto unit you should had replace these parts. Points, condensor, the points open to send a spark to your spark plug these should be set to a open gap seting when the cam lobe opens them. The condensor keeps the pionts from pitting or shall we say it cushions the arking of the pionts opening with current. Now if you have a 12vot (Distributor) you should have a coil. The coil is a unit with two windings inside it. These are primary winding (low ) and a secoundary winding (high). They only way to test it is really there is no test. You have to have the right equipment for that test. I would go by the age of it and if it is getting hat after the engine warms up. Good example is when the engine is cold runs great if coil gets hot and the engine starts to miss the coil is no good.

Champion spark plugs? Try a
different manufacturer. Newer
cap? The newer ones have
aluminum contacts instead of
brass like the older ones.
That aluminum likes to
corrode in the top where the
wires go in, usually in the
coil terminal, but sometimes
on the terminals that go to
the cylinders as well. Bad
ballast resistor if it has
one? This is just assuming it
has a distributor.

Ross

Unsure if wires are "solid core" will check, which may be why I have weak spark? Tractor does have coil and distributor, but has 6 volt battery/ unsure why? Tractor runs same cold or hot. You guys know your stuff, be busy in A.M. Thanks to all, any other info, pass along..

thought the solid core wires were only needed when equipped with a mag.? Bill

"<font color="#6699ff">[b:654c4848f0][i:654c4848f0]but has 6 volt battery/ unsure why?[/i:654c4848f0][/b:654c4848f0]</font>

The Model M and MT tractors were originally equipped with 6 volt batteries and all have a positive ground electrical system.

We have 6 volt batteries on "Sparky" our 51M and "Mac", "Rusty", and "Sam" all three of our 51MTs.

Agree with [b:654c4848f0]M-Man[/b:654c4848f0] that "[i:654c4848f0]BTW - BAD condensers are common as dirt now a day's so it's never a bad idea to swap it out when one is running rough even if it's new.[/i:654c4848f0]"

We are constantly replacing condensers on "Rusty" one of our MTs.

Take a look at the photo below.



Also agree with [b:654c4848f0]RBoots[/b:654c4848f0] "[i:654c4848f0]Champion spark plugs?[/i:654c4848f0]" and "[i:654c4848f0]Newer cap?[/i:654c4848f0]".

You might consider Autolite spark plugs.

Take a look at the photos below.





You might also consider checking the distributor cap.

Take a look at the photo below.



"Mac" one of our MTs was running rough and eventually died in the hay field.

Replaced the cap and rotor and solved the problem.

Also agree with [b:654c4848f0]brent zappe[/b:654c4848f0] that "[i:654c4848f0]if coil gets hot and the engine starts to miss the coil is no good.[/i:654c4848f0]"

We have replaced the coils on all six of our John Deere Dubuque tractors.

Hope this helps.