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Hey everyone

I just got an old riding lawn mower that I’m trying to get running again, it’s a Ariens Fairway model 912009, I believe it’s from 1976.

Im having trouble getting a spark, spark plug is fine and I have tested the coil and condenser with a multimeter the best I could. So my question is, have anybody seen a coil like this and know where to buy one?

This is what you are looking for, https://www.partstree.com/models/mg-610689a-tecumseh-magneto/magneto-0/. I must warn you that working on these Tecumseh engines is not for the average DIY guy. Please read the section of this manual, on ignition systems, before attempting any repairs or you could get some where you don’t want to be. https://www.mymowerparts.com/pdf/Te...P-4-CYCLE-L-HEAD-FLAT-HEAD-ENGINES-692509.pdf. 95% of todays small engine mechanics have no idea how to time these engines, once they have taken the ignition system apart. You’ll have to find an experienced mechanic over 50 years old, who has experience with these old engines. Sorry for this answer, but I must prepare you for what you are getting into. If you have more questions before you start please feel to ask.

Thanks for the very detailed reply!
I had the ignition system off, to try and measure a bit on it, I can still very clearly see the marks from the bolts so I can reposition it again, is that sufficient for the timing or did I screw that up?
And do you think it will be sufficient to only replace the magneto, I measured 7.33 resistance on 20k with my multimeter on the coils, does that sound about right?

How good a gambler are you? Once you remove the magneto assembly it is a crap shoot if you get it back correctly. I’ve always taught that measuring primary and secondary resistance on Tecumseh coils should be between 0-15 Ohms on the primary and 0-15,000 Ohms secondary. When measuring resistance you must have all three leads disconnected from the engine. Some techs don’t take the time to have all leads loose during testing, resulting in false results. Just my opinion, read my signature.

Well, it’s either that or it’s going to the eternal grass fields…
So do you have any tips and trick for removing the old and installing a new magneto? And again, thanks for all the help

Patience is your friend. Not very hard until you get to the timing. Reassemble the parts into the magneto first, install the assembly as close as you think you can, making sure wires will not catch on anything, set the point gap, I use .018”, install flywheel figure tight to set for spark with plug removed. You should be able to spin by hand, just make sure you watch your fingers. Can tell the times I’ve pinched them while testing. If you have spark, torque flywheel and test run. If it doesn’t run or runs rough, timing is to far off and you can go back to trying to move the assembly a fraction one way or the other. Good Luck in your endeavors.

Remove all ignition parts. Remove all corrosion from them. Polish said parts to clean metal. Polish mounting surfaces on the engine block. Clean all mounting screws to bare metal. Reinstall parts and test for spark.

Oil that thirst looking white wick that lubes the ignition points lobe.

Slomo, I don’t know how many Tecumseh engines, with internal magnetos, you have worked on, but if the OP follows your instructions his chances of success will go way down. When was the last time you’ve worked on one of these engines, if ever. If he does all the cleaning you suggest, he’ll remove any of the bolt marks he’ll need to set the timing, because he doesn’t have the tools needed to time the engine. Second, it sounds like he is going to replace parts, so why go through all that cleaning. Finally the cam wick should be lubed with cam lube, which is a waxy grease, not oil.

Rivets said:

Patience is your friend. Not very hard until you get to the timing. Reassemble the parts into the magneto first, install the assembly as close as you think you can, making sure wires will not catch on anything, set the point gap, I use .018”, install flywheel figure tight to set for spark with plug removed. You should be able to spin by hand, just make sure you watch your fingers. Can tell the times I’ve pinched them while testing. If you have spark, torque flywheel and test run. If it doesn’t run or runs rough, timing is to far off and you can go back to trying to move the assembly a fraction one way or the other. Good Luck in your endeavors.

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Timing is done with an offset dial indicator to piston .080" but I cannot remember if before or after TDC. Can be done with head off and normal vernier since I am probably one of 10,000 shops that still has the special tool to stick in plug hole with ofset shoe to measure pistoon position. Points should just open at the setting by ohm meter reading. I expect the manual can be down loaded on my site at http://vrr.dyndns.biz/Docs/Repair/linecard.html
The coil is a separate slide on part to the iron lamination on most.

I’ve got the other dial indicator. Always BTDC, but there are different measurements for different engines. Measurements are in the manual I posted.

So i changed the magneto and condenser, still no sign of a spark, any ideas on what to do next?

Vilfred95 said:

So i changed the magneto and condenser, still no sign of a spark, any ideas on what to do next?

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I tried grounding the condenser elsewhere and as far as I can see the magnets should be fine

You will need to reread the section of the manual I posted on ignition systems. I don’t understand why you would ground the condenser some place else? The condenser should be bolted to the stator plate and will be ground when you bolt the stator plate to the engine. Condenser lead goes to the points, along with the kill wire. Have you tested for spark with the kill wire disconnected?

I was out of ideas and thought it might be a bad ground, maybe I went about It the wrong way. I also tried it without the kill switch wire, didn’t seem to make any difference.
I tried to follow the troubleshooting guide in the manual, but unfortunately I have not been able to find the problem.
After installing the new components I hooked up the wiring as if was before, condenser+primary lead+kill switch wire to the bolt behind the points and the ground from the coil to bolt that is holding the condenser in place.

just looking at the original photo and not having the specs nor wanting to read a lengthy manual for someone else's project, the points gap looks huge in the photo. Maybe that is how they designed them I dunno. Generally if you don't get the points gap proper and clean that area up to have a proper installation you will never get a spark.They normally need some points lube also to keep the rubbing block from wearing out or the lobe.

I just went back and looked at the original picture you posted. I see two coils, one internal magneto and a second which looks like an external solid state coil. Which one are you trying to install? Second, did you replace the points and set the point gap to .018” after you have bolted the stator plate to the engine?

Ok, I’ll give this one more try, as if this engine came to me in a basket and I didn’t have a dial indicator, but I did have a VOM. I’m assuming that you have a new coil, points and condenser. I’m also assuming you have an internal ignition system and you have removed the spark plug. Before starting read the section in the manual I attach on timing you engine with a dial indicator. This will give you an idea of what we are trying to do.

1. Remove the old coil from the stator plate and install the new coil, making sure you install it with the secondary lead, primary lead and ground lead so they will be against the block (or down) when you bolt the stator plate to the engine.
2. Remove the old points from the stator plate and install the new points.
3. Remove the old condenser and bolt the new condenser to the stator plate. You must remember to install the coil ground lead bolted between the condenser mount and stator plate.
4. Install the stator plate to the engine and tighten. You said you have some marks on the plate and block which you can use to set at this time, if they are gone, center the bolts in the slots.
5. Rotate the crankshaft until the high point of the ignition cam is centered on the points rubbing block.
6. Set the point gap to .018”. Rotate the crankshaft three times and recheck point gap. If it has changed reset and repeat until it doesn’t change.
7. Clean the points with a quick drying spray contact cleaner.
8. Now check point operation with your VOM. Connect negative lead to the stator housing for a good ground. Connect the positive lead to the points post (where you will attach wires later). Set VOM to resistance or continuity position. Slowly rotate crankshaft in the correct direction and observe the meter readings. At first you should see an infinite reading and then a reading of 0 when the points close. Continue turning until you see the points just start too open and the meter should go back to infinity. If you achieve this you have set the points properly and they are working. DO NOT DISCONNECT THE METER LEADS.
STOP, TAKE A BREAK AND RELAX A BIT, AS THESE NEXT FOUR STEPS ARE EXTREMELY CRITICAL. YOU WILL NEED AN 1/8” WOODEN DOWEL, BRIGHT LIGHT, SHARP PENCIL OR SHARP KNIFE, AND SOME WAY TO MEASURE .090” WHICH IS APPROXIMATELY 3/32”. This is the distance I came up with to set timing on engines your size. DO NOT START STEP 9 UNTIL YOU FULLY UNDERSTAND WHAT YOU WILL BE DOING. THE POINTS SHOULD BE WIDE OPEN WHILE DOING THESE STEPS.
9. Insert dowel into spark plug hole and rotate the crankshaft back and forth until you have located the piston at TDC. GET THIS AS CLOSE AS YOU POSSIBLY CAN, BECAUSE IT IS VERY CRITICAL. Now you need to find someplace on the head to hold the dowel against, to be able to mark the depth on the dowel. I like using a knife as it gives me a fine line.
10. Now from this mark, measure up .090” and put a second mark.
11. Reinsert the dowel into the spark plug hole and check to see if your first mark still lines up where you held it on the head and your second mark is above the first mark. Hopefully they both are or you’ll have to redo your marks.
12. NEXT YOU ARE GOING TO ROTATE THE CRANKSHAFT BACKWARDS. HOLDING THE DOWEL TIGHTLY AGAINST THE PISTON HEAD, UNTIL THE SECOND MARK HAS DROPPED TO WHERE THE FIRST ONE WAS. THIS SHOULD NOW BE VERY CLOSE TO .090” BTDC. Remove the dowel but DO NOT MOVE ANYTHING ELSE.
Stop, take a break and relax. Your meter should still be hooked up and set to resistance or continuity.
13. Meter should be showing infinite resistance. Loosen the two stator plate bolts until you can rotate it with some resistance. Rotate the stator plate clockwise until the meter jumps to 0 and stop. Without moving the stator plate tighten the bolts.
Now if you have done everything right you have staticly timed your engine.
14. Attach the primary coil wire, condenser wire and kill wire to the points post. Double check all wires to make sure they cannot be caught by the spinning flywheel. Install points cover and flywheel as I described in post #6. Watch your fingers and check for spark. Hopefully you have spark.

Now I have a few things to add.
1. With a dial indicator it normally takes me 1-1.5 hours to do this procedure. To be honest, I did one that kicked my butt for two days. You need the patience of Job when doing it the first 20 times.
2. Having an assistant who understands what you are trying to do is not a cop out, it shows you’re learning in your old age, plus if everything goes right, someone to celebrate with.
3. If you have any questions about this procedure, please feel free to ask, before starting. Rule to my students, “Better to ask a dumb question than make a stupid mistake “.
4. If the engine runs rough, you may have to go back and rest the timing to about .080”.
5. If this doesn’t work I don’t know what to tell you to do next. Good Luck

That is a really good and thorough explanation, thank you for that! I will be trying it out in the weekend.

Just reread my procedure and found I missed a step, sorry about that. If you have spark after Step 14 you need to go back and remove the flywheel, it should only be hand tight, and clean the crankshaft surface and key. Now install the flywheel and key and torque properly.