Stihl MS460 Magnum no spark?

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Lar45

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Joined
Jun 9, 2023
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Location
Arkansas
Hi everybody, First post here.
I borrowed a Stihl MS460 Magnum chainsaw from a friend and it won't start. I dumped the old gas, put fresh gas 50:1 in and no life. I pulled the plug, put a new plug on and no spark. I went on Amazon and ordered a new coil for it. I installed the new coil, set air gap with a business card, and still no spark. I pulled the cutoff switch out and hosed it down with elec parts cleaner and disconnected both wires and still no spark.
I checked the wires with a meter and didn't have any grounded out wires.
The coil kit came with new wires, but one of them doesn't have the correct end on it. I could cut it off and put a crimp on connector, but the original wires look to be in good shape, so I didn't do that.
I'm not quite sure what to do next.
Any ideas or suggestions would be greatly appreciated.

I'm in central Arkansas and during a recent storm, we had a very large red oak tree get blown down across the back fence and into the neighbors horse pasture. I sort of needed the big saw to cut the root ball off of the tree and to get the main trunk cut into manageable sections so we can get it loaded onto a trailer and out of the neighbors pasture.
 
I pulled the spark plug, attached to the plug wire and rested it on the cylinder head, then pulled the start rope to see if there was any visible spark on the spark plug gap.
 
Disconnect the wire at the module. TThis eliminates all switch wiring. Make sure there is a good ground at the module mounting points. Set gap with a postcard. If all this is OK, you have a bad coil.
 
Hello again and thank you for the suggestions.
The magnets are strong.
I called the Stihl dealer and they said to set the air gap at .008-.012".
I set it at .010" with a brass feeler gauge.
I tried another new plug with the shutoff wire disconnected and spun the engine CCW with a drill and 13mm socket.
Still no spark.
So I'm sending it back and will try another new coil.
The Stihl dealer said a new coil was around $150!, but he didn't have one in stock. So I'll roll the dice on another China-Co coil and see what happens.
Last week I installed new Amazon carbs on a MS170 and MS290. Both fired right up and tuned easily.
The 290 only has a 20" bar and my oak tree is very large. If nothing else, we can try making cuts from both sides to cut off the root ball.
The 460 Magnum belongs to the widow of my friend that died of Covid a couple of years ago, so the saw had not been run in about 3 years. I'm pretty sure that he used Stabil in his saw gas, so I hope I won't have to put a new carb on it as well.
 
Hello again and thank you for the suggestions.
The magnets are strong.
I called the Stihl dealer and they said to set the air gap at .008-.012".
I set it at .010" with a brass feeler gauge.
I tried another new plug with the shutoff wire disconnected and spun the engine CCW with a drill and 13mm socket.
Still no spark.
So I'm sending it back and will try another new coil.
The Stihl dealer said a new coil was around $150!, but he didn't have one in stock. So I'll roll the dice on another China-Co coil and see what happens.
Last week I installed new Amazon carbs on a MS170 and MS290. Both fired right up and tuned easily.
The 290 only has a 20" bar and my oak tree is very large. If nothing else, we can try making cuts from both sides to cut off the root ball.
The 460 Magnum belongs to the widow of my friend that died of Covid a couple of years ago, so the saw had not been run in about 3 years. I'm pretty sure that he used Stabil in his saw gas, so I hope I won't have to put a new carb on it as well.
Put the old coil back on with the kill wire disconnected and try it in a dark garage. Use a new or known good plug with the correct gap. These small engines don't make bright sparks like your car. A drill may not spin it fast enough to produce a spark.
 
You're probably on the right track when you mentioned sending the coil back and getting another one. I, for one wouldn't spend a bunch of money to get an oem coil.
Used OEM coils should be readily available on Ebay and they come with a 30-day functionality guarantee.
 
IT's Alive!
Amazon delivered a new coil today. I installed it and spun the engine with a drill and had spark!
I put it all back together and it tried to fire up on the first pull with the choke on. I took the choke off and it fired right up, but wouldn't throttle up at all. The chain was stuck in the bar from old oil. This saw probably hasn't been run in atleast 3 years-ish.
I pulled the bar and chain off, put the chain to soak in some oil and wire brushed the bar out. With the bar off, the engine revved just fine, but didn't want to idle. When I get it back together, I'll try adjusting the carb.
What's the consensus about running carb cleaner in the fuel? Just wondering if the low side jet might have some lacquer build up not letting it idle?
Thanks again for all of the suggestions.
 
I don't put anything in my fuel except 2 stroke oil. I guess you could mix it a bit leaner but I wouldn't go too lean or you'll have an engine to rebuild. I would try adjusting it first and let it run a while as the fuel will tend to clean the carb as it goes through it. I hope you're not using ethanol...
 
For a carb that's just been sitting around for years, I sometimes have good luck by just removing it and soaking it submerged for 24 to 48 hours in a jar of good mixed fuel. Amazing how that sometimes (but not always) solves problems in a dirt-cheap fashion. Can't hurt to try it.
 
IT's Alive!
Amazon delivered a new coil today. I installed it and spun the engine with a drill and had spark!
I put it all back together and it tried to fire up on the first pull with the choke on. I took the choke off and it fired right up, but wouldn't throttle up at all. The chain was stuck in the bar from old oil.
This shouldn't have happened unless the previous user was using vegetable BIO oil which can self polymerize if it sits too long. This may gum up the oiler system. Others may have some ideas on how to clean out BIO oil.

With the bar off, the engine revved just fine, but didn't want to idle. When I get it back together, I'll try adjusting the carb.
I am assuming that this saw has limiter caps on the screws. If so they should be full CCW to the stops if cutting near sea level.

What's the consensus about running carb cleaner in the fuel? Just wondering if the low side jet might have some lacquer build up not letting it idle?
Thanks again for all of the suggestions.
You might try using a small metal tag wire to clean the idle and transition holes in the carb throat. AVOID removing the welch plug in the carb as they are nearly impossible to reseal afterwards.

Failure to idle could also be an LA screw adjustment, old gas, or possible air leak. A video of the saw at idle and WOT would help diagnose.
 
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