Yeah the thing about the 7-10s is there now appears to be two different cylinders well 3 actually if you count the cast bore. The two chromed cylinders have an open and a bridged transfer. Would be nice too know if the bridged is really the apparent slower 700 cylinder or weather the bridged 7-10 still has some other differences.
My open port 7-10 has alot of missing chrome and is done really but still runs great. The 700 has a good score and is not what it should be so I have no real performance comparisons. The two good 7-10s are both bridged and pull very hard I might add.
The 10-10S engine I have is apparently the same as the 555 the (pm55 is points)
That 57cc is in a completely different league to the 54 and is definitely alot more than 3cc would suggest it's a screaming little saw the 54 seams to just fall off in high rpm and seems to sound thin and lean and does not have the grunt at all if tuned like that. The 57 just loves the rpm yet still has a mean bottom end too. Its really not very far away from my good 7-10s.
I can't praise it enough.
A couple weekends ago I had a good race session with my mate and his ms311 and that S is right with it every time. In smaller 10 inch wood his has a little edge in 16 to 20 the 57 is every bit as fast and he has to be gentle on the stihl it's right on the edge of bogging but the 57 can lean all ya like and nup no slowing it up at all.
In real world cutting when his chain is going away that's it put it down and sharpen but the Mac will pull that chain happily till the tank is done.
We all know that's not what you should do but when there's 6 cuts left of the log and you still got oil just give her some extra pumps and get it done.
I have a spare 54cc block with a groove in it and I'm wondering about boring it to the 57cc piston and attacking it with a dremel to copy the S as best as possible. Be nice to know the bore measurement of the pm60 perhaps there is enough meat to go that far I suspect not though.
I've also read a few times the 57 is a bit more sporty compared to the 60 perhaps the 60 is ported more like a 54.
Anyway bla bla alot of out loud thinking going on