Hot-rodded the MS201T. Much better now

[Sodo]

I bought an MS201T in 2013 and have NOT been happy with it. Took awhile but I figured out how to fix it reading posts on Arborist forum. I followed the posts and it's a little hotrod now. Basically did 4 things.

1) Bent a little lever up (like a float valve lever but it's on a diaphragm).
2) drilled a hole in the muffler
3) filed the flywheel key a little to advance the timing. Site recommended 6-8degrees but I did about 4*.
4) defeated the limiters on the "mixture adjust" screws

Anyway it's a LOT snappier now and pulls HARD with the bar buried. I am impressed. It kinda has some 'run-on' when I let the throttle off. I can't get this to go away, it's like a mid-range leanness, not affected by the high or low screws.

Any tips on tuning the H/L screws? I got the initial settings from the Arborist site, but don't know where I'm at right now. Will put them back and start over. Apparently this saw is difficult to tune the "H" because it's electronically rev-limited. I've been choosing a setting based on how hard I can push on it with the bar buried, then open it 1/8 turn further, and it still has that lean 'run-on' when I close the throttle. And it sorta 'runs dry' after ilding a little while.

 

[MF283]

hmm, i need to check that forum out & see what i can learn. Which one is it?

Ronnie

 

[motownbrowne]

I bought an MS201T in 2013 and have NOT been happy with it. Took awhile but I figured out how to fix it reading posts on Arborist forum. I followed the posts and it's a little hotrod now. Basically did 4 things.

1) Bent a little lever up (like a float valve lever but it's on a diaphragm).
2) drilled a hole in the muffler
3) filed the flywheel key a little to advance the timing. Site recommended 6-8degrees but I did about 4*.
4) defeated the limiters on the "mixture adjust" screws

Anyway it's a LOT snappier now and pulls HARD with the bar buried. I am impressed. It kinda has some 'run-on' when I let the throttle off. I can't get this to go away, it's like a mid-range leanness, not affected by the high or low screws.

Any tips on tuning the H/L screws? I got the initial settings from the Arborist site, but don't know where I'm at right now. Will put them back and start over. Apparently this saw is difficult to tune the "H" because it's electronically rev-limited. I've been choosing a setting based on how hard I can push on it with the bar buried, then open it 1/8 turn further, and it still has that lean 'run-on' when I close the throttle. And it sorta 'runs dry' after ilding a little while.

I think you should be adjusting the H screw either with a tachometer, or by listening for 4-stroking out of the cut. The saw should 4-stroke until it hits wood, and then clean up. Otherwise it's too lean.

I'm glad you got it running better. Those are supposed to be very nice saws once you get them properly modified. Too bad Stihl didn't do that from the factory...

 

[Sodo]

MF283 send me a PM if you don't find it I'll find the posts I used. Wasn't really sure how many were interested here. Watch for a name "B Snelling" he's extremely helpful. Theres a european guy who explains the electronic rev limiter & bending the little tab for more fuel. I don't know what B Snelling says about that fuel step but I did it. Might be the cause of my tuning problem. Search YouTube for B Snelling, or MS201T, there are several vids by BSnelling.

I think you should be adjusting the H screw either with a tachometer, or by listening for 4-stroking out of the cut. The saw should 4-stroke until it hits wood, and then clean up. Otherwise it's too lean.

I'm glad you got it running better. Those are supposed to be very nice saws once you get them properly modified. Too bad Stihl didn't do that from the factory...

OK thanks for that tip. Yes I've read that, but I couldn't make sense of the tip when my saw wasn't running. Now that I'm in "tuning mode" I'll figure it out. So, once I find that point where it goes from 4st to 2st, do I richen it a little more, or leave it there?

The arborists are claiming now that the modded 201T is actually more powerful than the old venerable 200T. With 200Ts selling for $800 and 201Ts for half that, the mod makes a lot of sense.

To get the flywheel off I loosened the nut one turn. Then flipped the saw so the flywheel was downward and gave the crankshaft one sharp rap (upward) with a small hammer and it popped off its taper.

The flywheel key is cast into the flywheel, so you have to file cast aluminum. It's dicey to do this and not scratch the tapered surface. There's a couple degrees of slop in the key, I suppose some saws could run better simply for where they are 'assembled'. You could just twist yours to the most advanced and retighten. This is a 5 minute job (just under the pullstarter).

 

[motownbrowne]

OK thanks for that tip. Yes I've read that, but I couldn't make sense of the tip when my saw wasn't running. Now that I'm in "tuning mode" I'll figure it out. So, once I find that point where it goes from 4st to 2st, do I richen it a little more, or leave it there?

When it's properly tuned, it will 4st out of the cut and clean up as soon it touches wood. I don't have a tach, and I'm a relative beginner at tuning saws, so I actually like to hear mine 4st once or twice in the cut. This ensures that it's rich enough. I could probably get a little more power by leaning it up a touch, but I don't need to ride the edge. I don't want to burn up a saw.

One thing to be very careful of, though, is saws with limited coils, like your 201. It's possible to mistake the sound of hitting the rev limit as 4-stroking. There's some good vids on arboristsite about tuning a rev limited saw. Basically, I'd suggest putting on some muffs, warming up your saw (can't tune it until it's warmed up) and playing around with it. By leaning it out, you'll learn where the limit is and then richen it until it burbles. Then lean back out until it just cleans up. Then back a touch richer (more if you're not 100% sure where you're at) and that should be a decent setting. Even a tiny turn off the screw makes a big difference. Remember, without a tach, err on the side of too rich.

 

[Sodo]

OK thanks. Assume the top-end 4st will be at the max RPM but I will be tuning at a lower RPM where the saw is pulling hard in the wood. I use a square shank screwdriver pretty easy to note 1/8 turns. Thanks again, your second post of tips was great too.

 

[motownbrowne]

OK thanks. Assume the top-end 4st will be at the max RPM but I will be tuning at a lower RPM where the saw is pulling hard in the wood. I use a square shank screwdriver pretty easy to note 1/8 turns. Thanks again, your second post of tips was great too.

Yep, lean it all the way out (scream) and listen for the 4 stroking. That's not 4 stroking, but it can be mistaken for it. That's the Rev limiter. Don't let it run there for long!! Also, you don't want to set the H screw while actually saying. If you set it for absolute most power in the cut, that'll be too lean. Gotta try a setting, touch it to the wood, see if it cleans up. If not, lean it out a 32nd of a turn, etc. Once you think you've got it, start cutting. While in the cut, loft the saw out momentarily. You should hear immediate 4-stroking. If it easily cleans up in the cut and 4 strokes out of the cut (not hits the limiter) then you're golden.

Of course, a tachometer is a reasonably cheap way to be perfectly sure where you're at.

Good luck!

 

[Sodo]

MF283 here's where I got my hotrod info:

MasterBlaster MS201T mods - Page 87
and
Aboristsite MS201T mods

Also note Stihl made some MS201 upgrades at serial number 17_7543232, I think around March 2014?. Mine is the "old" (before the upgrade). Stihl gave away the upgrade for awhile but kept it quiet. The shop I bought mine from was never notified, but they also wouldn't acknowledge my complaints, they said just said everybody loves the MS201 what the heck am I complaining about. I don't know if this mod is appropriate for the "upgraded" MS201.

After awhile Stihl sold the upgrade kit for about $200, but I think they no longer sell it. The upgrade was a new carb, an ignition module and a different flywheel (AFAIK). I have read in some places that "the mods" are better than Stihl's upgrade.

Motown this is just in time. Thanks again! What tach do you recommend? All the tachs I see look like you have to plumb it in, is that how you have to do it? Got your tips loaded into my phone. Will tune it today or tomorrow.

 

[sd455dan]

I bought an MS201T in 2013 and have NOT been happy with it. Took awhile but I figured out how to fix it reading posts on Arborist forum. I followed the posts and it's a little hotrod now. Basically did 4 things.

1) Bent a little lever up (like a float valve lever but it's on a diaphragm).
2) drilled a hole in the muffler
3) filed the flywheel key a little to advance the timing. Site recommended 6-8degrees but I did about 4*.
4) defeated the limiters on the "mixture adjust" screws

Anyway it's a LOT snappier now and pulls HARD with the bar buried. I am impressed. It kinda has some 'run-on' when I let the throttle off. I can't get this to go away, it's like a mid-range leanness, not affected by the high or low screws.

Any tips on tuning the H/L screws? I got the initial settings from the Arborist site, but don't know where I'm at right now. Will put them back and start over. Apparently this saw is difficult to tune the "H" because it's electronically rev-limited. I've been choosing a setting based on how hard I can push on it with the bar buried, then open it 1/8 turn further, and it still has that lean 'run-on' when I close the throttle. And it sorta 'runs dry' after ilding a little while.

still has that lean 'run-on' when I close the throttle. And it sorta 'runs dry' after ilding a little while.[/QUOTE]

I have only done (limited) tuning on my chainsaws- but used to do the jetting for my brother and some friends when they raced motocross with 2 stroke bikes,
I would try richening the low speed screw a bit to counteract rpm hanging- once the throttle is snapped shut , since it should be running on the low speed circuit.
On a larger 2 stroke, increasing the pilot jet size and re adjusting the idle mixture screw would have been the ticket, at least that has been my experience with rpm hanging after the throttle is closed.

 

[Sodo]

SDdan your jetting experience sounds similar to mine.