I'm posting this for my brother but am familiar with the situation. He has a MS250 he purchased used. Saw ran fine up until recently. Now, it will run for a while then stall with no spark. He checks spark after a day and it is fine again and will run until warmed up. Sounds like a bad coil, simple enough fix. He orders a new one online (not sure of brand or where) and finds that he gets no spark. He re-installs his old one and it sparks fine. He calls the company and they send him another one. Same exact problem. Two new coils, neither seem to work. He's a little tired of buying coils and was hoping for some more suggestions. It consistently sparks when tested cold and losses spark when warm. Is there anything else besides the coil that could cause this? He can't believe he got two bad coils but doesn't know what else to think. Thanks in advance.
MS250, two new coils, no spark????
- Thread starter skidud
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John R
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Is the wire that goes to the stop switch touching the engine block and shorting out when the engine gets hot? Maybe some melted insulation on the wire.
Kwdog75
Addicted to ArboristSite
Either the wires are bad or the flywheel, check both and get back to us.
Saw Dr.
Junk Collector
Have you tried a new spark plug? Do the new coils come with a wire? Could be a bad connection of the wire on the new coils. Maybe a new section of plug wire is in order too.
New coils came with wires. He isn't using a plug but rather an ignition tester to check spark. Not sure about wires or magneto. I'll tell him what you guys said and have him check all that stuff. I'll try to post some more tomorrow night. Thanks
He emailed me late last night that he got spark with one of the new coils. The thing is, he had to set the clearance at about .002" where as the stock coil was set at .011". I don't know what the minimum clearance should be but .002 seems pretty tight. I'd personally be leery of running anything spinning that fast at a tolerance that close unless it were designed to do so. I thought around .010" was a good clearance but maybe I'm wrong. Do you think he ought to try another coil or just run it like that? Does that seem like a poorly wound coil to require that tight of tolerance to produce voltage?
wse8562
ArboristSite Operative
First off, are you sure this is the right coil? If so pull the flywheel and check the key. If someone ever tried to remove clutch by banging or using an impact it could be sheared. Also check wire from kill switch to coil, especially the round connecter where it contacts the spring.
Saw Dr.
Junk Collector
A sheared key will not cause no spark on an electronic setup like this. It will change the timing and ability to run, but not the spark. I would try a new flywheel. If the coil sparks with tight clearance, something is up. You should be able to set the coil air gap (approx .012) with a business card and have it spark normally. How fast are you spinning it to check spark? Sometimes a power-drill is just a tad too slow for an electronic coil. Gotta love points. They'll spark just rolling it over with your hand.
wse8562
ArboristSite Operative
Right you are! I was not thinking! Thats even worse than when I do. Could be bad flywheel,rare but possible. I would check that kill wire though!
sefh3
Addicted to ArboristSite
Get some emery cloth and touch up the flywheel. Take a business card and set the coil and see what happens. If your gap is too close you will not get a spark.
All excellent points guys, I'm gonna send him a link to this thread. Thanks for your help. I'll be sure and report back to close out the thread when we get to the bottom of it. It may be a little while though.
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