For you guys that run an 880 on a mill and using a tach---what RPM do you mill at? This thing is tached at 11000rpm max no load (yes the book on this one says 11000 max no load). It seems to mill best at between 6000 and 7000 RPM. That seem too slow to me. What are you getting with yours?
This also has one of the new cast iron mufflers and it sure seem to be runnnig hot--as in the heat seems to boil off the saw. The dealer says it must be the muffler??????
Thanks for your input,
That's very interesting because 6000 rpm is where the stock 880 supposed develops is greatest torque - but as you will see below this RPM is not where you should operate the saw. As well as the performance characteristics of the engine, optimum milling speed RPM is dependent on a number of other factors including things like wood hardness, size of cut and chain settings.
Leaving cut size, engine characteristics and wood hardness aside for the moment;
If the chain has too much hook and/or the rakers are too low then the saw will have to be held back or it will bog down - this translates to fastest coolest milling being done at higher RPM.
If the chain has too little hook and/or the rakers are too high the saw will need to be pushed to cut anything which loads up the engine reducing RPM. At lower loaded RPM there is also less cooling so the saw runs hotter. I can see my saw clearly running hotter if I push it because I have a temp gauge on my saw,
I haven't milled with my 880 in completely stock form so I don't know how it compares, so my comments from here on related to my 880 which has a significant muffler mod, 19 mm versus 14 mm stock opening or an increase of 84% that exhaust can escape from. I then tune my saw slightly rich so max RPMs are 11.5k
Now that I have more experience with my 880 I realize my original comment of 10.5 - to 10k should have been "overall optimal cutting speed" rather than "fastest cutting speed"
With 6º chain cutting angles in my big hardwood, if I sit on 10k and push the saw hard it will initially cut much faster than when I'm just sitting on 10k, but then the RPMs drop and eventually at around 7 K the cutting speed slows to less than what I get at 10K. This would seem to say that I should find an even sweeter cutting speed spot somewhere in between the 7 and 10k, but it doesn't always work out like that - if I push it very hard the engine bogs down in a couple of seconds, if I push it just a little, it will still slow and usually it continues to slow and eventually bogs down. It might take 5 seconds or 10 or 20s to slow but it will slow. Now I don't want to be standing there bogging and unbogging the saw all the way through every cut. This generates an uneven finish and bluntens the chain quicker, and more significantly, heats the engine more than necessary. In practice, one does not wait until the saw has bogged and as it begins to slow of course one backs off the pressure so the RPM catch up again. Bear in mind that every time it's catching up it's not cutting as fast as it could.
If I sit the engine on a constant say 10k, the engine is getting good air flow, it's constantly cutting with a great finish and I get to the end of a slab without exerting much effort, with the chain still moderately sharp at the end. In practice if I adjust my leg pressure to push it a touch more and maybe operate in the 9.5 - 10k range it cuts a bit faster without a lot more significant effort. If I push like a demented bull and continually range the saw up and down the power range, both I and the saw end up all hot and bothered and in practice I don't end up cutting any faster overall and we just wear out for no good reason.
