Hydro - V's - 2 stroke power - V's - 4 stroke
After experimenting with all sorts of power propulsions for CSM's, Band mills and 2 strokes, here is what I have found.
Hydro is a very expensive route to take, it does have very smooth delivery and the power to match, but I feel it has its work cut out, please excuse the pun, to compete with the other ways, unless you already have the pump and motors to hand.
2 stroke is by far the most common and easiest to apply, and one thing I have mentioned many times before is, by reducing/converting your existing chain size down to a smaller pitch greatly increases your cutting speed, take the M7 for instance, she uses a 50 patern chain, my freinds unit is driven by MS 660 Stihl, very quick through the log.
Starting out with a new CSM and the size if saw needed to cut comfortably is not cheap and takes the longest to re-coupe because of the relatively slow speeds involved, but this system cannot be equalled by any other for there absolute portability.
A little off topic, but I would like to add, We have also been using 4 stroke power to drive a trailer based CSM, similar to the Procut mills, the power unit is the Honda GXV 13 hp motor electric start, things are coupled to the chainsaw bar via a simple conversion plate and driven by a harvester sprocket direct to the chain and bar, the advance is also electric.
In recent tests the 4 stroke out performs the Hydro system, and is relatively cheap to buy new compared to a big 2 stroke saw motor.
I do not have many pictures of the 4 stroke system yet, the tailer seen here comes in two 10 foot beds which fasten together giving a 20 foot platform, the rolling saw frame is very similar to my Log-Saw band, mill I will post more pictures of the 4 stroke set up once I have perfected things more.