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Ms 201 m-tronic stalling issue

NateSaw

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So we have two ms 201's. Both have timing advances and muffler mods. 1 I ported. Both keep stalling. The one that's not ported, started stalling shortly after the timing advance. I advanced both 7*. They run great (especially the ported saw) on throttle. But they will not idle. I've been through the carb on the non ported saw. I found debris and rebuilt it, replaced filter, lines, and cleaned tank. The ported saw is currently running on my fuel, which is new, 40:1 hp2 87 octane. My can is rarely on the job so it's insulated from the debris and abuse our companies cans are subjected to. The house fuel is 50:1 shiot 87* stens oil. Both saws have been pressure/vac tested and only the usual throttle shaft weaping was found... All you blokes have more experience than I... So, I'm reaching out for darts to be thrown my way. Thanks! (I have a theory I should undo timing advance as a test)
 

Junk Meister

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I won't be much help but do they (Both) start easy ? and any noticeable differences after you cleaned the debris in the stock non ported saw?
 

NateSaw

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I won't be much help but do they (Both) start easy ? and any noticeable differences after you cleaned the debris in the stock non ported saw?
Yes they both start easy. And frankly, yes there was a difference after I cleaned the fuel system on the stock saw.... For me. But when Brandens radioactive ass runs it, it won't idle 🤣🤣
 

NateSaw

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I also forgot... I did replace the carb on the stock saw after the cleaning of the og carb didn't seem to hold.
 

huskihl

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I had one here that was idling too high. Passed pressure and vacuum tests, tried a new solenoid, tried a new carburetor. Ended up replacing the coil to fix it. So if you end up needing another mtron 201 carburetor, I have one here
 

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Try putting the screen back in. Sometimes they want a little back pressure.

201 carbs are a pain. I’ve had about 50% success rebuilding them. Not sure why.
 

NateSaw

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I had one here that was idling too high. Passed pressure and vacuum tests, tried a new solenoid, tried a new carburetor. Ended up replacing the coil to fix it. So if you end up needing another mtron 201 carburetor, I have one here
Thanks Kevin... We had discussed coils. I might just get one. I mean, that's the ecm. I did also forget to mention I had put a solenoid in the stock saw.
 

NateSaw

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Try putting the screen back in. Sometimes they want a little back pressure.

201 carbs are a pain. I’ve had about 50% success rebuilding them. Not sure why.
Thanks Caleb! Are you referring to the muffler screen? Both saws have holes drilled in the muffs. The ported saw I hogged nice nice.
 

Junk Meister

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Slim chances especially when you have 2 saws and 2 (different) gas cans. The debris under the screen looks like varnish or busted up roach/bug shells. Is it possible the tanks each got a dose of crud from a gas can that was filthy? And the screen is plugged again?
 

SCHallenger

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I have an early 201 (standard carb) which has been ported by Kevin. The only time it had any stalling issues was when it was stock. It is running on canned fuel ( VP 94 octane with Motul 710 @ 40:1) & is flawless!
 

NateSaw

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The most problematic 201 (the non ported saw)... I had cleaned the screen, blown out the carb, I did put the screen back of course... Blew out the lines, replaced filter. Problem disappeared for a bit and came back. Then I pulled carb apart again, found no debris, reinstalled, problem was still present. I had another used carb on the shelf, pulled it apart and cleaned it, installed that. Thing still stalls, but again, only for Branden when he's in the bucket. The ported saw, rarely stalls, but does on occasion. I'm with Kevin. I'm leaning towards a coil on the non ported saw. I've got them both to wear I can't find a speck of debris in the fuel systems... Not saying there isn't some migrant shiot making random visits... But then how come the entire rest of the fleet of saws have no issues? This is why I'm scratching me arse. To me, the main thing these 201's have in common, that were both done at the same time, was the ignition advance. I wondered if these become finicky on the m-tronic side when advanced....
 

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It’s very easy to set the advance back to stock so it’s worth a try. Are they dying when you drop the throttle or when they’re just sitting at idle?
You replaced the solenoids?
 

NateSaw

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It’s very easy to set the advance back to stock so it’s worth a try. Are they dying when you drop the throttle or when they’re just sitting at idle?
You replaced the solenoids?
Yes the most problematic one got a new solenoid.
 

NateSaw

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What color?
I'll have to look. Black I believe. That's what the local dealer sold me. I said to them I thought there was an update. It didn't look different than what I took out, iirc.
 

Ketchup

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Black is what Stihl lists for the 201. Considering they’re almost always the ones that fail, I usually replace with white or green, but black should be fine. Have you swapped carbs from the ported saw to the non?
 
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