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Got a crank/no-start on a snapper push lawn mower with briggs and stratton 2 stroke engine, separate oil/gas.
I have no prior history of this lawnmower, other than “it just doesn’t work”, but it seems like a good ruggedly built mower… just got to get it to work.
Here I diagnose no spark:
Since there is no spark, I immediately suspect the coil. Now, it’s just a matter of getting to the coil
Disassembled discharge shroud, upper cable guard and gas tank:
Taking off engine cover:
Exposed flywheel, magnets, and coil:
And… at last, the coil:
Just waiting on replacement parts… in the meantime, i will be doing a lot of cleaning around the engine, air filter, carbuerator and exhaust.
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when most people try to start a 2 stroke engine…. they crank and crank and crank until they are blue in the face.
the whole day, I only pulled on that engine 4 times. B)
I had a no spark there also this spring. I just cleaned the rust off the spark plug wire from the coil and cleaned up the spark plug and it fired right up. Left it outside all winter uncovered. Runs like a champ now, mowed 3 times already this year with it. Always starts with 1 pull after I give it a couple pumps with the primer bulb.
Installed the coil.. gave it a test pull expecting to see amazing blue flashes of success… and got nothing! So I sat there looking stupid kinda thinking about what could still cause no spark.. and while I was thinking I tapped on the magnets with a screwdriver.. and noticed that one magnet was very weak. So I pulled off the flywheel and will go in tomorrow and see if they can maybe magnetize it somehow or just order a new flywheel:
New coil at the cost of $44:
New coil installed via a highly technical process of obtaining the .010″ gap:
This magnet tested very good:
This magnet is deader than dead:
Now I need to remove the flywheel:
The real culprit – a bad magnet:
All I need to do now is throw one more part at the problem and I will have replaced the entire ignition system. 🙂
working on this problem up until this point has been kinda fun. went to put the flywheel back on, and the damn nut wont go back on the crankshaft. something stupid like this always happens. the nut came off just fine, why won’t it go back on? spent 3 hours last night trying to get it back on and then decided to drink beer.
just dumped a bunch of money into thread repair:
Now to find a replacement nut. This could take days of trial and error. The first 3 I’ve tried thus far have not worked. The parts people at the local small engine shop also have no clue.
pictures are kind of blury. I wonder if this mower has the lever you hold while mowing and once you let go it kills the engine. If not weak magnets can cause the problem. You will have to replace the flywheel.
the magneto system is very simple; magnet spins by coil, coil reaches a threshold voltage, internal transistor opens, magnetic field collapses and spark is created.
using my DVOM, I was able to determine that ‘something’ is happening when I spin the wheel, but it doesn’t appear to be enough to create spark. Therefore, I have to assume 1 of 2 things are happening:
1. magnet is weak. although this is unlikely, and feels pretty strong to me, I have to take this into consideration.
2. got a bad coil out of the box. there are 3 possible parts listed for this engine during the part search. i’ll take it back at some point and switch it out for another coil.
I wire wheeled spots on the engine block to get good ground. the flywheel is spinning clockwise as per normal operation. I also wire wheeled the posts that hold the coil. For added measure, I disconnected the kill switch connection to the coil to eliminate the possibility of a short to ground.
For such a simple system, I am pretty much at a loss as to why I am unable to make electricity.
after replacing the entire ignition system, and trying a second coil (armature) I am still unable to produce any kind of spark:
the only thing now that I can think of, is high resistance in the ground circuit. To resolve this, I my just solder jumpers from the bottom side of the coil to a couple of points on the engine block.
take a dummy light, put put the clip on the connection for the coil and probe the killswitch,try to start it normally. if the lights not blinking when you pull, you might have to get a new killswitch. alot of the times you can just clean them up.
I’ve done all my testing and experimenting with no kill switch connected to the coil at all. New flywheel, powerful magnet, 2 brand new coils = an entirely new ignition system.. and no spark. I tested the flywheel spinning in both directions. I even tested the coil upside down. I guess it just wasn’t mean to be, so I found another solution:
FYI bonus information:
There are two circuits available for grounding out the coil: one tied to the stop/run switch and another tied to the “operator presence safety lockout” handle bar that grounds the coil directly to the fly wheel through the flywheel brake. I’ve tested both of these circuits and they both operate as advertised.Sorry to interrupt, but you might find this one useful over at DonnyBoy73. The small engine doc where he explains that before replacing the ignition module you check the gap between the flywheel and the module along with the wiring, etc.
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