I tried it on a tire a couple of years ago and all I did was set the tire on fire.
Stihl MS-261C M-tronic with weak spark
- Thread starter scottieamn
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I tried it on a tire a couple of years ago and all I did was set the tire on fire.
Flywheel magnets are polarized, they are opposite of each other meaning one is north and the other south...they both should strongly pull a steel bolt to them....using a magnet one should strongly attract the magnet and the other should strongly repel it. Yes they can go bad by loosing their magnetism or even reversing polarity. Typically is the second or south magnet that fails when the flywheel stops for long periods with the magnet clocked against the coil pickups or heat kills them.. With the plug out to test spark it should be very easy to archive the 250-300 rpm needed to trigger a strong spark. It sounds like you have poked at and prodded everything but the flywheel so I'd go balls deep and get a used or new oem one coming then report back to the mob on here once replaced and retested...leaving only the harness left to replace.
Do the part numbers on the old and new coil match? Did you check the wiring harness with an ohmmeter? Did you gap the coil?
He should check the harness with a meter first.
Unless I missed it in the email chain I still don’t see replacing the coil.
He did OEM.
I think you correctly diagnosed the problem as ignition. Compression issues take time to develop unless you have a mechanical failure like a broken wrist pin retainer, and when that happens you pretty much know instantly you have a serious problem.
i‘m pretty sure Ive got a 261CM flywheel or two laying around that I can loan you to troubleshoot with, along with a puller. I’ve never heard of a flywheel going bad but poster Lone Wolf says he has seen it, so it is worth it to me to see if that could be the issue.
I'm curious why he is determined not to look at the piston.. Hell, that's the first thing you check.
Guessing because he can’t get spark. The odds of it having both a lack of spark and a scored piston as the reason it won’t start are pretty slim
Well, I work on about 50 saws a week. And, what the owner says is the problem is seldom reliable. And, they all say they know everytrhing there is to know about it.
So' look at the ******* piston. Rule that out.
I understand. I would also. Personally, I think he’s just not pulling it over fast enough to get spark.
Listen to the experts you came here seeking....if you were qualified, you'd have a forum.
scottieamn
ArboristSite Lurker
Thanks for all the feedback. You guys are right. I should have checked the piston.
I get a weak spark when pulling hard. In my experience a good working ignition will make you flinch when finger is on spark plug. I get a mild tingle when pulling hard. Or sometimes no spark at all. Do saws only make a tingle sensation when touching plug?
Also, as already stated above and caused controversy, I put gas mix in jug and then replaced plug and got nothing when pulled. Then starter fluid and nothing. Unless I have a hole in the piston I would think weak spark would make fluid fire it up momentarily.
I also agree with responses about new starter fluid not being a real danger. But didn't want to debate since these are my first posts here.
I do have the technical ability to diagnose a normal saw easily, these m tronics are new to me though. Thinking it is wire harness since spark is sometimes weak, sometimes non-existent.
I'm out of the country for another week so I won't have any feedback until then.
Thanks again all
I get a weak spark when pulling hard. In my experience a good working ignition will make you flinch when finger is on spark plug. I get a mild tingle when pulling hard. Or sometimes no spark at all. Do saws only make a tingle sensation when touching plug?
Also, as already stated above and caused controversy, I put gas mix in jug and then replaced plug and got nothing when pulled. Then starter fluid and nothing. Unless I have a hole in the piston I would think weak spark would make fluid fire it up momentarily.
I also agree with responses about new starter fluid not being a real danger. But didn't want to debate since these are my first posts here.
I do have the technical ability to diagnose a normal saw easily, these m tronics are new to me though. Thinking it is wire harness since spark is sometimes weak, sometimes non-existent.
I'm out of the country for another week so I won't have any feedback until then.
Thanks again all
No, it won't.
scottieamn
ArboristSite Lurker
It was indeed the wiring harness. Thanks all
Me too. It's complete bull shat. I've used break cleaner as starting fluid many times. If only because I no longer have ether on hand.
It's hard to seat beads with starting fluid nowadays. Napa brand will still do it.
Greg Poole
ArboristSite Lurker
Did you find which wire or connector in the harness was causing the issue?
If it was one of the wires, where was the break in relation to where the wires are routed?
SteveSr
Addicted to ArboristSite
The computer in the coil checks for wiring harness continuity. If it fails it kills the spark.
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