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MS261CM M-Tronic Issues and Many GFY’s

RI Chevy

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Just me Ryan. No sweat dude. It's all good...
 

dall

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ChipsFlyin

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Maybe here's why taking the squish up to 20 worked. This chit had me thinking and lead me in a simple give and take direction. Primary function of the MT - feed fuel and monitor RPM related to where the throttle trigger is depressed. Under load 20" 0r 25" bar - throttle is depressed fully but rpms are down leading to the MT feeding more fuel resulting in a rich mixture. On top of that the actual area for ignition of fuel mix with a higher mix 32:1 is way down with a squish of 15 resulting in incomplete ignition- not enough air in the space. Thinking that way what happens if you take a saw up to say 22-24? You loose a bit of compression but can you really load the saw up with maintaining even more RPM in the cut?
 

huskihl

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Maybe here's why taking the squish up to 20 worked. This chit had me thinking and lead me in a simple give and take direction. Primary function of the MT - feed fuel and monitor RPM related to where the throttle trigger is depressed. Under load 20" 0r 25" bar - throttle is depressed fully but rpms are down leading to the MT feeding more fuel resulting in a rich mixture. On top of that the actual area for ignition of fuel mix with a higher mix 32:1 is way down with a squish of 15 resulting in incomplete ignition- not enough air in the space. Thinking that way what happens if you take a saw up to say 22-24? You loose a bit of compression but can you really load the saw up with maintaining even more RPM in the cut?
The fuel that remains inside the squish band is wasted. It doesn't combust to make power. That's why we're trying to make the squish smaller. But it's just a little bit too much heat in there for the m-tronic to compensate for it. With a bigger squish it runs a little cooler somehow
 

ChipsFlyin

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The fuel that remains inside the squish band is wasted. It doesn't combust to make power. That's why we're trying to make the squish smaller. But it's just a little bit too much heat in there for the m-tronic to compensate for it. With a bigger squish it runs a little cooler somehow
Thanks. What about a cooler plug?
 

huskihl

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Thanks. What about a cooler plug?
I'm waiting right now for a softer diaphragm for the carburetor. A cooler spark plug is my next move. I also believe that higher octane fuel would probably tame it down. The owner of the saw actually runs 100ll, so that will probably help it also
 

ChipsFlyin

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The 462 I had here had a colder than standard plug I believe if I’m not mistaken. 6 instead of the 7. 6 is the colder plug and 7 the hotter plug.
Interesting. I know doc likes his tight squishes. Might be worth a swap to see what happens. Might help finalize a build recipe.
 
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