MS 441 Hop-up?

Hey Guys:

Our shop has two 441's that are universally hated by everyone who has to use them--mainly because of their power to weight ratio, but, there are other reasons. They've had them tuned up twice by the saw shop, but there's been no real improvement.

I ported my ms 440 a little while ago, and they were so impressed with the power gains, that they asked me if I could hop-up the 441's.

I know absolutely nothing about these new emissions friendly monstrosities. Anyone care to help me out of the misery I might be getting into. Can anything be done?

Throw them out and buy 460's.

Damn if I don't love Bill right now
But there are gains to be made, albeit not the same gains you get from a non-strato, but the ports and transfers can be cleaned up, and a muffler mod really helps them as well.
Just DO NOT get crazy with porting them! As I understand it, it's a fine line before you mess up the port timing to a useless saw!
I hope Timberwolf will chime in, I know he's done a couple and can share some wisdom on this!

I've heard tell of several who have had some degree of success with this engine design .I have not however seen one personally .

The 441's I have seen and tested ran good woods ported for a 441 (they are what they are). There are gains to be made over the anemic stock 441 and a woods ported one can be leaned on. With all the extra work and expense you can make a woods ported 441 run like a stock 7900.

Put it this way a woods ported 441 would be like running a stock dolmar 7900 (just trying to get the comparison right so you could understand what I was trying to say). 441 still falls short of a non-strato saws like a 460, 372 that is woods ported by a pretty wide margin.

Yeah... The idea of doin' the transfer ports is the scariest part for me... Junk as they are--boss wouldn't take it too kindly if they never ran again!

Oh..... And what does "Strato" mean?

Its means inferior epa approved saw.

inbredJed said:

Oh..... And what does "Strato" mean?

Click to expand...

Timberwolf could explain the technical terms, I cant.

Here's a look inside a strato to see the difference.

<iframe title="YouTube video player" width="480" height="390" src="http://www.youtube.com/embed/IY7zQKw4qsQ" frameborder="0" allowfullscreen></iframe>

Well I'll be damned I didn't know that's how it works .In practcality it's similar to an air injector pump used on auto engines .Of course naturally it's a two cycle engine so modications are neccessary .

So evidently then the air must be shoved out ahead of the fuel /air charge to provide the neccessary level of o2 to burn off the exhaust .At the same time enough of the fuel/air with some oil in it lubes the bearings in the crankcase .Rather ingenious for the intended purpose .

As the negative pressure changes within the crank case evidently that would determine how much air and how much air/fuel it would suck in from the way the graphics indicate .--or I'm just as confused as the next guy ---

Al: You'll never be as confused as me. Thanks for the link, though, Cut4fun.

Al what it is doing is putting a layer of clean filtered air between the fresh fuel mix in the crankcase and the left over ex gases in the combustion chamber, so the air scavenges the ex out and holds the fuel back for the fraction of a second it takes to let the piston come up and close the ex port. Now the fuel comes in and it doesn't leak out of the ex port as scavenge loss of unburnt fuel. The ex is measured in a dyno lab and a number is calculated as grams per kilowatt (or horsepower) hour. So when a MS 440 is tested it comes out at 120 g/kWh, and the MS 441 comes in at 67. So this saw is heavier but has almost the same HP but will cut a bit longer on the same amount of fuel and pollute less which really should matter to us, and I am not a greenie tree hugger but I do still want to be able to run internal combustion engines 20 years from now, so I guess we need to take some responsibility for cleaning our little engines up. The EPA said back in 1996 that one chainsaw put out as much pollution in an hour as 10 cars doing 60 MPH down the highway for an hour, so that is why they put a gun to the indusrty's head and gave them from 96 to 2007 to basically cut the average emissions in half for hand-held engines above 50cc, and smaller engines had to go from about 250 to 50.
This is why most new designs are stratified scavenge models at least as far as STIHL is doing it. The MS 261, 291, 391, 362, and the new 201 all are this way but the newer models are lighter and simpler to work on.
SO back to your 441. If it is tuned correctly and running right it should perform about as well as a 440. If you open up the muffler and fatten up the carb you probably will see a little improvement in performance but I have not tried it myself, but I guarantee you the fuel economy will drop tremendously so you might as well stay with the older saw. The cylinder does have some complex port timing with 6 ports to direct the scavenge air, and the muffler and the dual butterfly carb and the porting are all carefully tuned as a system.
Make sure the saw does not have any air leaks or fuel system troubles and try tuning it like this:
Gently warm it up. With a tach set the idle to about 3300 RPM, then find the lean drop off point with the L screw. That is where the RPM drops off lean if you go clockwise any further, and also starts to drop off when you go rich by turning the L screw out. Once you find the L screw lean drop off point and the idle is at 3300, then use the L screw to fatten up the idle to get to the desired idle speed of 2800 RPM, not the idle speed screw. Once you get that done you will find that the saw idles well and will have crisp throttle response and is at it's optimum mixture setting for idle and off idle. Then go to wide open throttle (WOT) just long enough to see what the tach says, don't hold it there very long, and go from rich towards lean to get to no higher that 13,500. The module will take away every 8th spark above that so you can get too lean but it won't over-rev, so always go from rich, say around 11 or 12 K up to 13,500. If the carb doesn't tune sensitively then there is a fault in the carb or an air leak or something else wrong. When I tune a 441 this way it runs good, so try it and see if the man has any better luck.

Thanks for the explaination Eddie .I had pretty much had it figured out I just didn't have any way to put the math to it prove or disprove my stab in the dark .

It would make sense using my way of thinking that because the fuel/air mixture was being drawn into the crankcase at a time when the differentual pressure was the greatest that this would be cooled by the ventuii effect .

Conversely the air charge took place at the upper portion of that cycle and passed through a hot piston widow .It would make sense then that the air would have a higher temp and thusly enter the cylinder at transfer first before the air/fuel .

Pretty neat idea I'll say that . I have no doubt within a short period of time about all two cycle engines will use a similar design as per EPA edicts .Most likely in addition it won't be too long before they use electronic fuel injection about like every other internal combustion engine .

As far a souping one up ,that too will come given enough time .That you could about bet on do to the very nature of gearheads .

Aha I see said the blind man as he picked up a hammer and saw .Now it's getting more clear .

It would make sense that because a normal two cycle uses a portion of the fuel/air mix to scavenge the cylinder that it would blow raw fuel .Now this thing,441 uses air for same and just stuffs the fuel charge for power .Hmm makes sense it would use less fuel .How 'bout that .

Yes Eddie: Thanks a ton for the comprehensive explanation, and the time out of your day. I deeply appreciate the very valuable tune-up advice as well. I'm thinking I won't mess with this one--at least not the transfer ports. Would I be a complete jackass to hog out the intake and exhaust ports a wee bit?

I see that you're in Virginia. Is there any national chain where I might get an inexpensive tachometer? Your help's been most appreciated.

I feel regarding any change to the ports, the margin for error is very slim on this saw. You may or may not see a noticeable change in power but you will probably see a drop in fuel economy, if that matters.
The best tach nowadays is the Sendec, and it will work on these new microprocessor ignitions where several other cheaper tachs I have just get confused. The STIHL version of the Sendec is around $90 I think so if you can do better at Baileys or Madsens then that would be the best place to order one.

Thanks!

Found a strato stihl video.

<iframe title="YouTube video player" width="640" height="390" src="http://www.youtube.com/embed/3LDN0c2lAsQ" frameborder="0" allowfullscreen></iframe>

This is a great thread.
I've been running Stratified saws for the last few years ( am currently on my second 441) and never had any idea about how they worked.

Thanks, guys.

I think it's a neat design myself .However after deciphering this thing I do think Eddie is right .Just keep it in good tune and run it .

Like I said before Tom who was reluctant at buying one finally secumbed and did so .The biggest reason was he got it for just about dealers cost the last day one of the Stihl dealers was in business .At any rate he ranks it a step above the 044 it replaced .

That 044 would not even come close to my 038 Mag but the mag has been enhanced and the 044 was stone stock,muffler and all .The new 441 won't out run it either but that's not saying it runs badly .It gets the job done and that's what counts and puts beans on the table .

Plus it vibrates a hell of a lot less, and the airfilter only needs cleaning once a week instead of every day.

I love the 441.

Im mad at Stihl these days. Im honestly less than impressed with anything they have come up with in the last few years. Where I work, I have the option of carrying a 441 all day, falling and bucking tops, or a 660. I just carry the 660. It gets heavy but the 441 drives me nuts.