Don't know if it's much help to you, but I've read here before that a decent benchmark for the size of saw to use is log diameter x 3.

So 40" diameter x 3 is 120cc saw. I may be wrong, you might have better response asking the question on the arbtalk milling forum.

There's a relationship with bar length and cc, but it kind of amounts to the same thing as log diameter, especially with milling. Could also go 8 tooth sprocket and skip chain 

The relationship is the maximum bar length in inches is 1/3rd of the cc so 60cc is 20", 120cc is 40" etc. Generally, most will go for a smaller bar.....20" on a 70cc etc but this is just a basic rule.

Surely the more powerful-for-their-weight modern saws have kind of seen that one off?  My 70ccc Echo pulls a 28" bar with ease - it's the manufacturer's recommendation - but it would manage a 32" I reckon; that's not far short of half engine size.

Or is that an exception?

I would say that its cms > cc. So your 70 cc echo would run a 70cm bar max (28). So by my reckoning the max bar ratio is dividing by 2.54, but 3.0 probably will result in nicer handling.

My suggestion was - perhaps wrongly - that the 1:3 ratio is out of date.  My Echo pisses its 28" bar; there's no 'nicer handing' about it!  Thinking about it I recently sold my 89cc 064 (why?!) and it's being used on a 36" bar; nae problem!

Tolerance of blunt teeth will be virtually zero though when you're pushing the bar length limits; you'll need to keep that chain sharp

Sorr

17 minutes ago, nepia said:

My suggestion was - perhaps wrongly - that the 1:3 ratio is out of date.  My Echo pisses its 28" bar; there's no 'nicer handing' about it!  Thinking about it I recently sold my 89cc 064 (why?!) and it's being used on a 36" bar; nae problem!

Tolerance of blunt teeth will be virtually zero though when you're pushing the bar length limits; you'll need to keep that chain sharp

Sorry I didn't mean it was absolute max, clearly you can run any size bar you want within reason depending on what you're cutting and yes I would assume that my 70cc saw could run bigger than 28s. But from what Ive seen recently it seems like saws are being listed with roughly cm > cc as the recommended max size (including echo's 70cc saw)

👍 🙂

It is just an old rule of thumb, there will always be exceptions and views will always differ plus the chain type and kerf makes a big difference but it is round about right and gives some indication or a starting point for the uninitiated and that is all.

I have always used the example Steve posted . The 60cc divided by 3 = bar length in inches 18" . As Steve says its a guide . It kinda suggests what the compromise is between balance and efficiency . Of course you could  put a a 24" bar on a 30cc saw and if you were gentle it would cut albeit slowly . It would not be efficient though .

Was kind of hoping for a recommendation of a possible saw . will need to look at the tree again, but the next one will probably be  different size, so so hoping there would be someone on here that would have experience of my dilemma. 

9 minutes ago, Sawbones said:

Was kind of hoping for a recommendation of a possible saw . will need to look at the tree again, but the next one will probably be  different size, so so hoping there would be someone on here that would have experience of my dilemma. 

Ideally to mill something approaching 4 feet across you want an MS880 or MS881.

They are massive cumbersome things and unnecessary for practically all UK tree work though, so you need to be realistic as to how much future large milling you are going to do.

An MS661 will happily pull a 36 inch bar all day and is adequate for just about any tree you’ll need to deal with in this country, and is a much more manageable saw than the 880/881. I’m not sure how well it would fair milling 40’’ logs every day but there will be others on here with experience of whether it is possible for the odd big log now and again.

Thank you Monkeybusiness, that is the kind of advice I was looking for. Saw with a 36 inch bar is probably what I need and can always take the edges off and not worry about a live edge. Would only be part time milling and big stuff.

To the op, I think you'd benefit from reading the 'todays milling' thread by ' Rough Hewn ' on here and also the many videos and much advice offered by Rob at https://www.chainsawbars.co.uk/

I joined this forum looking for similar advice, there are many on here with much experience and I for one am still benefitting from that.

I'm not milling commercially, more of an opportunist enjoying saving nice bits from the firewood pile.

I use an ms650 [ a few cc less than the 660 and just what turned up at the time ] mounted in a 48" Alaskan mill, with this setup I loose about 6" off the bar length by mounting it in the mill.. I've got  25", 36" and 42" bars the later 2 being probably oversize for the saw.

I think from memory that 42"  x 3/8" bar is the biggest bar available for the 660, I know that I'm pushing my luck but I try to be careful and keep the chain as sharp as fecking possible and so far no probs, but speed of cut depends greatly on the timber I'm milling, there's a huge difference between fresh Cedar and long dead dry Oak or Ash for instance.

From what I've read [on here] in the todays milling thread, if you're going to be milling 40"  it looks like the new ms881 might fit the bill best, but there are older big saw alternatives you have the skills to keep them alive, I always fancied the Husky 3120 but one never came my way...

So if you're buying new look and making a living from it, I'd say look at the 881,  good luck👍