I guess I have some questions and opinions on the matter of how hard milling is on a saw...
One question (Maybe BobL can help here) is once a saw is warmed up how long does it take for the exhaust temp (or cylinder temp) to level out when milling? I.e. When does the saw reach its maximum operating temperature? 30 sec, 1 min, 5 min, 10 min? If the temp keeps rising over time, then I'd say extended runs are to be viewed with caution, if it plateaus in 2 minutes, I'd say anything beyond 2 min isn't going to be any worse for the saw, as a saw is certainly designed to run that long without excessive wear and tear.
Unless the cut gets noticeably narrower (eg you mill up the log) or the chain hits a patch of pukey wood, if a constant forward force is applied (eg slope milling) I found the temperature never really plateaus but rises quickly and keeps increasing slowly during the cut. This is because the chain gets blunter and the saw has to work harder. Some of my cuts in 40"+ wide aussie hardwood can take 20 minutes. The temp gauge is very useful to see what is going on in these long cuts. There is also a natural tendency to want to finish the cut asap so the operator tends to push harder at the end than the beginning and that also increases the temperature significantly. I can push harder and watch the temp gauge increase in about 3-5 seconds. Using or not using aux oil also affects the engine temp.
In terms of temperature what most operators do not realize is how long it takes a hot saw to cool down.
As soon as the saw stops cutting the temp as recorded by my gauge (in contact with the outside/top of the exhaust manifold shoots up for about 15-20 seconds as the engine cannot be cooled fast enough by the fan.
After a long hard run it takes ~ 5 minute to get the engine back to initial idling temp (which depends on ambient temp). I used to only cool it 30 seconds but what I was doing more recently was let it idle till for maybe 2 minutes at the end of the cut.
I also have a TS-400 cutoff saw, and I know that these can be bolted to a cart and run continually for scoring / cutting concrete and I don't know that to be any worse for the saw. Stihl designs these saw to be run like this I assume. Is there that much difference between the two (besides filtration)?
There is a difference, cutoff saws don't go anywhere near as blunt in cuts as chain does. I don't have a lot of experience with cutoff saws but my understanding is once the cutting edge is gone, its gone and pushing just doesn't do anything
In terms of filtration, the dust produced by a saw milling, is more likely to plug / bypass the filter, thereby causing damage to the saw or poor performance so in this sense, I think milling exposes a saw to more potential damage... so be particularly dilligent about keeping the filter in shape and sealed. (Fuel and oil filters too)
Maybe it's because I mill mostly green logs but I cannot think of one example where I cleaned a dirty filter and noticed a difference in temperature. I usually only clean my filter at the end of a day of milling green logs and maybe 2-3 times during a dry log milling day. However I do always try to mill with the wind at my back and on the 880 (and to a lesser extent the 076, the modified exhaust blows the sawdust well away from the saw. On the 880 I never have to walk in more than 1/2" of sawdust while milling even a biggish log.
Most of the problems with too much dust on the filter of a milling saw I have seen on other peoples milling saws seem to me to be related to chain sharpening issues and making dust versus chips. Mostly they just don't touch up often enough or their rakers are too high (ie don't use progressive raker setting).
I agree with you on using the 50:1 with fully synthetic if the saw is kept well tuned and the mix is made carefully every time. I use 40:1, highest octane premium gas, and non-synthetic, mainly because I find it hard to get synthetic, and the 076 is speced at 40:1 and I don't want to continually keep a range of mixes for different saws. If I had access to synthetic I would probably use 50:1 even with the 076, I think BlueRider does this.
In practice cooking a saw is the sum of a bunch of factors and it's when these align that problems arise. For newbies and folk with lackadaisical attitude or limited skills in things mechanical I always recommend 40:1. For mechanically skilled operators they could probably mill successfully at 60+:1 using synthetic and high octane premium.
As for tuning, its one of those factor it's best not to be wrong about so I prefer to err on the side of caution and drop the max revs a few hundred rpm. I like to see the plug on the darker side of medium brown (hard to do because the idle cool down changes the colour) but I will occasionally stop the saw after 5 minutes in the cut and check the plug.
