MS 441 M-Tronic conversion

[morbius18]

I've seen a few older threads concerning switching a plain carb MS441 to an M-tronic. Most threads ended with it being cost prohibited.

I had previously replaced the covers from an mtronic unit. So they are interchangeable with no issues. The carb setting decal is different and the decal for control lever positions has the mtronic 3 position symbols instead of the carbed 3 symbols.

I also converted to ms362c-m/ms261c-m bar studs so I could have the clutch cover with the captive nuts. I used a 362/261 clutch cover.

Saw prior to transformation:



I picked up a MS 441c from ebay that had a tree fall on it. Tank/handle was missing and clutch side rear AV mount was broken off:


I got the original saw off here and really wanted to do this conversion. This thread is more to document this for others that might want to do it.


The IPL shows the parts needed, which were all good on the parts saw.


Older standard carb flywheel case on top, mtronic one on the bottom. I though that I'd just use my original case, but I was wrong. Below are the differences with the square cutout on the mtronic one. Screws are also different sized; mtronic is m4x20 vs standard carb m5x20.

Standard carb case:


Mtronic case:


Mtronic case half on right, standard carb half on left:

 

[morbius18]

Mtronic ignition on right with screws and standard carb on left with screws. Mtronic has the additional control wire for the fuel solenoid.


Mtronic carburetor on right, standard on left:



Mtronic flywheel on right, standard on left. The mtronic one has an extra set of magnets on the opposite side of the ones marked N & S for the spark.

 

[morbius18]

The filter base has a small notch cut out where the control lever sits on the mtronic unit on the right.


Carb housing box has a few differences for the control wire to be routed. Mtronic on right:


Control lever has a different shape which engages the choke and the shaft. I mistakingly used the standard one and it didn't click off the choke setting. Mtronic on right:

 

[morbius18]

Mtronic filter on the right. It has a knob with a stud in the filter that screws into baffle. The standard on the left has the stud on the baffle with the knob separate. Interestingly, this isn't on the IPL as different.


The side grommet cover is also blank:

 

[morbius18]

Mismatched cased passed pressure and vacuum tests. I did use Dirko HT red along the crankcase seal and both sides of a thinner .010" base gasket as insurance:


Only difference were the routing of wires:

 

[morbius18]

While I had the saw apart, I adjusted the squish. I had .013" without base gasket. I used .010" paper and got .023". I filed .020" off the flywheel key. I opened up the exhaust port, port matched the heat shield and muffler. I cut gills, removed the spark arrestor and opened the muffler hole.

 

[morbius18]

I replaced the carb gaskets and assembled it. It took about 10 pulls to get it to fire. Did the reset and calibration procedures.

1. With the chain brake engaged…
a. Hold throttle and set start lever to Start position (Δ)
b. Start saw and let idle in Start position (Δ) for 90 seconds
c. Blip throttle to bring the machine to the Run position (I)
d. Immediately move lever to Stop position (O)
e. This will reset the carb to original factory setting.

2. With the chain brake engaged…
a. Hold throttle and set start lever to Start position (Δ)
b. Start saw then Blip throttle to bring the machine to the Run position (I)
c. Let idle in Run position (I) for 90 seconds
d. Immediately move lever to Stop position (O)
e. This will calibrate the idling characteristics of the saw.

3. With the chain brake engaged…
a. Hold throttle and set start lever to Start position (Δ)
b. Start saw then Blip throttle to bring the machine to the Run position (I)
c. Disengage chain brake and make five uniform cuts through a minimum 12-inch-diameter log.
d. This will calibrate the full throttle characteristics of the saw. Done.

Mtronic conversion was successful and easily adapted to the mods on the saw.

After conversion. (I know that superficially it looks the same, but I did use a black paint marker on the recoil sight line):


It's like a completely different saw now, feels like it has quite a bit more power.

One disappointing thing, was that I had to remove all the arctic heated handle stuff. A mtronic arctic flywheel isn't very cheap and being in Tennessee, not very common.

 

[DND 9000]

Mtronic filter on the right. It has a knob with a stud in the filter that screws into baffle. The standard on the left has the stud on the baffle with the knob separate. Interestingly, this isn't on the IPL as different.

The previous baffle 1138 120 4100 including the slotted nut 1138 140 9500 you have was replaced with the newer baffle 1138 120 4102 and twist lock 1138 140 9300. Change was in 2010. On your picture the left one is the old version and on the right the new version.

 

[Joshua K McCoy]

Curious how much it cost for the conversion

 

[morbius18]

Curious how much it cost for the conversion

I got a parts saw from ebay. Like 150 or so. I sold the other parts to bring the cost down. You almost need a parts saw or the cost will be prohibitive. I did it more do so if it could be done.

 

[Joshua K McCoy]

Thanks I apologize after reading it again I seen you had bought a parts saw I had a bad internet connection at the time thanks for info.