Putting Stihl’s highest-performing saw in the 60 cc range – and the first in the world with a magnesium piston – to the test.

AS usual, there’s going to be a short history lesson before we get into the saw talk. But before even that, I have to deal with the big fat elephant in the room.

E10 fuel. Nobody likes it, but we have little option but to use it. While E5 fuel was the norm there was the option of super unleaded, but now even that has gone, or at least the stuff they call super unleaded now is really E5, so the direction of travel is clear.

I have done some research (well, I contacted Stihl as I’m reviewing one of their saws) and learned that Stihl M Tronic saws can and will run happily on E10 (10 per cent ethanol). In fact, they are okay up to 25 per cent ethanol, which would suggest to me that the days of E25 fuel aren’t far away. All other Stihl petrol equipment is also compatible with E10 fuel.

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There are caveats, however. This only applies to saws that are relatively modern. Stihl states this applies to anything built since 2003 and you must not store fuel either in the machine or in cans for more than 30 days. It’s also recommended (and common sense) to drain E10 fuel before storing equipment like saws, lawn mowers, strimmers etc, and then run them on an alkylate fuel to flush the system as a final step. In my opinion – which is reasonably well informed – you can forget fuel stabilisers and wonder additives as they don’t work.

With that out of the way, we can get on to the job in hand. Stihl has always had a 60 cc professional-grade saw in its inventory while I’ve been involved in forestry. The first one

I used was the 036 (the 038 was popular, but it wasn’t a full pro saw) and while this was a popular machine with some cutters I worked with, I always found it fell between the two dominant Husqvarna models, the 54 cc 254 and the 66 cc 266. It was too big to brash with and not powerful enough to fell hardwood and bigger softwood with.

All this changed with the introduction of the MS 361. This was a light saw with more power and better ergonomics than its predecessor. It would do most jobs and run everything from a 13” bar up to an 18” bar and use 3/8” pitch chain. It produced 3.4 kW/4.6 hp, weighed in at 5.6 kg and had class-leading vibration figures of 2.9/3.6. The 361 still had a manually adjusted carburettor and as such it was familiar to my generation of cutters, being the first Stihl, in my opinion, to match the Husqvarnas of the day on every level.

Forestry Journal: This particular saw has been well used over the last few months, by multiple cutters.This particular saw has been well used over the last few months, by multiple cutters.

The next 60 cc saw to come along from Stihl was the MS 362 and, despite having the full scavenging engine that offered more torque, it had very similar weight and power statistics with an identical power-to-weight ratio to the 361 of 1.6 kg/kW. It couldn’t match the 361 on usability though, and this was obvious in the front- and rear-handle vibration figures. The 362 couldn’t match the older saw at 3.5/3.5 and it showed. Stihl put this down to having to reduce runtime on the new saw because it was so fuel efficient and to do this it reduced the tank capacities. While the slight decrease in smoothness was something many people neither noticed nor cared about, I had hands that had put in many hours felling by then and I did notice, and so I didn’t ever own or use an MS 362, despite testing two different saws over long periods.

I rated the MS 361 one of the best saws I’d ever used. I had several of them, but this was at the tail end of my days when I considered myself as a cutter first and machine operator second. I gave up on the 60 cc saws after using my first MS 441, and after a couple of them I finally landed on the MS 462 as my preferred saw. Much of my reasoning was that we were now felling more and more hardwood, particularly diseased ash. The power, balance and smoothness of the 462, even running a 20” bar, was perfect for me, to the point of preferring it to the MS 500i which, while undoubtedly a masterpiece of engineering, didn’t have the ‘just so’ feel of its less glamorous stablemate.

The MS 400 is advertised as being the newest of Stihl’s 60 cc class saws. This has become a very important class in recent years. There isn’t the huge pool of cutters in forestry harvesting anymore and the type of work has changed significantly. There are people out there who are hung on a saw all day, but the bulk of harvesting is now done from a seat, not from on the ground with a chainsaw.

There has been a shift. With more work being specialised to fit in with mechanical harvesting, edge trees, steep ground and sensitive site work now make up much of what chainsaw operators find is their bread and butter. We are finally seeing better rates and the welcome end of piece work for hand cutters. Diseased ash clearance is starting to become a large body of work – a hazardous but lucrative one for those who have the experience and know how to do it. With all these changes comes a general change in saw capacities. The 500i just scrapes under the 80 cc mark and, as is the general trend, the CM 400 at 66.8 cc makes it nearer 70 cc than 60, but the performance is what stands out and what people note. After all, it’s how good the saw is, not what cc the engine is, that matters.

It’s becoming common practice to pitch saws at the top end of their capacity class, but looking at the figures this isn’t an issue for me. The CM 400 is 200 g heavier than the 362/361, but it is a whole heap more powerful. It boasts 4 kW/5.4 hp compared to the 361’s 3.4 kW/4.6 hp and, most importantly, I’ve found it can happily turn a 20” bar even in hardwood.

So it’s light and powerful and has similar ergonomics to the 462 with its powerhead being quite long and low. With no big hump at the back, it feels easy to handle and does throw about nicely, making snedding a fluid operation that was a characteristic of the 361, but something that was sadly missing in the 362.

The 400 is a very capable saw. It has power and usability, and has the very durable Stihl cutting gear: bars that don’t bend or wear rapidly and chain that doesn’t stretch and, while not the easiest to sharpen, cuts well with relatively good edge retention.

This is everything you’d expect from a saw that is a new design rather than a reworking of an older model, but it is the list of features that really make it stand out (and I’m not usually a fan of a long list of features that may or may not be marketing tools).

The magnesium piston for example. Is it really necessary? What benefit does it offer? What’s wrong with aluminium-alloy pistons?

There are two important points to be made here. First, the piston is not magnesium. It’s a magnesium alloy called EN-MB MgAl9Zn(A)(AZ91). Secondly, the piston in the MS 400 is not forged but die cast, and that process allows for thinner, lighter piston walls and crowns.

The new, lighter piston is able to accelerate faster. It absorbs less energy because it takes less power to move it up and down in the bore, and it provides a lower reciprocating mass, which is what produces much of a saw’s vibration. Reducing the weight of the piston means you can reduce the weight of the crankshaft journals needed to balance it.

Forestry Journal: The cold starting on the 400 is remarkable, but it is let down by the lack of a version with a heated handle.The cold starting on the 400 is remarkable, but it is let down by the lack of a version with a heated handle.

Magnesium alloy also has lower thermal expansion rates than aluminium alloy and the more precise die casting process allows tolerances to be finer, so a magnesium alloy piston can be worked harder without seizing, especially as magnesium alloy melts at a higher temperature than aluminium alloy. Magnesium pistons in other applications do have a tendency to gall or pick up on cylinder bores, but as chainsaw cylinders are plated with a low friction material such as Nikasil, this shouldn’t be a problem here.

The MS 400 is a very feature-heavy saw, as I’ve already mentioned, but for me the lack of a heated handle version is a real let-down. It has the usual side tensioner for the chain, the tool-less filler caps, captive bar nuts and the pre filter in the fan cover where air is forced into the top cover, which are all features we now take for granted, but it has some other less common touches.

The cold starting is quite remarkable. The control lever has a cold-start position, which is simply set to choke and left alone. A couple of tugs on the starter handle and the engine starts and can be revved to full speed immediately. There is no routine that requires choke on, pull ‘til it fires then choke off and pull until it starts, then pull the trigger to disconnect the fast idle. With practice, the MS 400 will start from cold by putting the lever to the choke position and giving it a single pull. Starting is further aided by the decompressor and the now-familiar elastostart pull cord. This is all brought together by the M-Tronic system, which also keeps the fuelling spot on even in varying conditions and using different quality fuels. Coupling the M-Tronic system with the 2-mix engine is claimed to give 20 per cent more torque and up to 50 per cent lower emissions.

One issue I’ve always had with Stihls is the quite indifferent design of the air filters, but the message has perhaps finally hit home as the 400 has a new air filter system Stihl calls HD2. This is a big filter made of some pretty advanced materials that are water- and fuel-resistant. I have found that brushing the air cleaner with a paint brush, then a spritz with a proprietary cleaner followed by a blow through with an air line works well.

An added bonus here is that removing and refitting the large air cleaner element requires no tools and is easy to do by even the most inept among us.

Stihl has produced a technically excellent saw in a class within a class. This is a 70 cc machine hiding in the 60 cc class. It is smaller and lighter than a 70 cc saw, but it is more powerful than a 60 cc saw. It’s a bit of a throwback, but it’s a class leader (at least technically). But how is it when it’s used in anger?

To begin with, I didn’t like it. I loaned it to another contractor who was felling reasonably big final thinning pine and larch. He was impressed, but not so enthusiastic he tried to hang on to it when I asked for it back. I planned to use it on a job we had coming up in the spring, but then a little problem called COVID-19 reared its ugly head and suddenly all bets were off. I didn’t really get to use the MS 400 until we started felling ash this summer. I changed the bar in it for an 18” one and bought a couple of new chains, and off I went.

When I started using the saw in the spring, it had already done a lot of work and had been through a lot of operators, all using it for a couple of weeks here and there, but finally I got to use it for a prolonged length of time. This is no two-week review of a brand new, shiny saw. This MS 400 bears the scars of battle and I wouldn’t like to hazard a guess at how many hours it’s got under its belt. What I can say is it has survived it all very well and I rate it as one of the most significant new models Stihl has produced.

Okay, it’s not the stand-out machine everyone talks about, like the MS 500i, but this is a brilliant all-round saw for jobbing cutters, part-time users, firewood producers or just someone who needs a single saw to cover many different aspects of the job. 

Yes, it revs like an absolute banshee, and that’s one of the most common criticisms I hear about it, but so far the one I’ve been using has been totally reliable. It’s quite an old saw now, but it still starts well, it’s smooth and produces the same power as it did on day one. It has held together and is as handy to use as any 60 cc saw I’ve ever used and way handier than most 70 cc saws.

I like it. In fact, I like it more and more every time I use it. It’s grown on me and if I were to have only one saw in my van it would be a toss-up between this and an MS 462.

The only reason I’d not choose the MS 400 would be the lack of a heated-handle version.