Big CC Chainsaws a thing of the past or will new models come out soon?

[Robin Wood]

No. Not by itself.

If there's a change in compression, change to combustion chamber shape,  swap to single ring or some other thing then maybe but weight change by itself will not give more power.

Plus it might screw up the balance of the engine and you'll feel it as extra vibration - those counter weights on the crank didn't get to be the size they are by accident.

 

Edit: Meteor pistons seem to work well, often tighter squish by a few thou over oe piston. Piston skirt length isnt always same as oe piston. Small changes but sometimes these little bits add up in the right direction.

 

I never understood the concept, but few porters and repairsmen have said the same thing to me. Lighter piston means more rpm and tq

 

The balance of top and bottom is negligible i think? AM big bores have heavier piston and they dont cause much vibe issues. On stihl 1106/09 series when you convert 070 58mm kit to 66mm, crank stays the same. But the piston gets an extra whooping 8mm increment, weight is increased by few folds here

 

 

 

[bmp01]

I wonder if they did any meaningful testing ? Cut times in wood all seem a bit inaccurate to me when you're looking for a few %. 10 % and maybe you'd see changes if you're careful with keeping everything else the same.  Most likely if the saw feels zippier (out of the wood) the builder claims success.... A lighter piston or crank could feel a bit like that.... maybe....

 

Re balance - it's not a precise science. The counter weights should balance out all of the rotating mass plus a percentage of the reciprocating mass.  Rotating mass is the crank pin, brg and the big end of connecting rod. Reciprocating mass is piston, gudgeon pin, brg and small end of connecting rod. Percentage ? Less than 50% for a 2 stroke. There's no exact number.

8mm change on piston diameter - you'd think that would weigh more, assuming piston design is same in both, they might have put big one on a diet ?

 

 

 

 

[Rough Hewn]

I never understood the concept, but few porters and repairsmen have said the same thing to me. Lighter piston means more rpm and tq 
The balance of top and bottom is negligible i think? AM big bores have heavier piston and they dont cause much vibe issues. On stihl 1106/09 series when you convert 070 58mm kit to 66mm, crank stays the same. But the piston gets an extra whooping 8mm increment, weight is increased by few folds here
 
 
 

You can put a 156?cc pot and piston on an 070/090 base.
Stihl made 5 or 10 back in the day as promotional saws at shows in the USA.
[emoji106]

[Cut4fun]

Guys here have 70mm pistons for their race saws.

 

Pics of friends for some big  cc saws

 

 

 

 

[Cut4fun]

70mm

 

 

[Robin Wood]

On 28/11/2020 at 19:32, Rough Hewn said:

You can put a 156?cc pot and piston on an 070/090 base.
Stihl made 5 or 10 back in the day as promotional saws at shows in the USA.

Yes mate, the 10 cube 090 which supposedly had 70mm were made in a limited amount. Maybe 10 units, they're monsters

[Robin Wood]

On 28/11/2020 at 18:37, bmp01 said:

I wonder if they did any meaningful testing ? Cut times in wood all seem a bit inaccurate to me when you're looking for a few %. 10 % and maybe you'd see changes if you're careful with keeping everything else the same.  Most likely if the saw feels zippier (out of the wood) the builder claims success.... A lighter piston or crank could feel a bit like that.... maybe....

 

Re balance - it's not a precise science. The counter weights should balance out all of the rotating mass plus a percentage of the reciprocating mass.  Rotating mass is the crank pin, brg and the big end of connecting rod. Reciprocating mass is piston, gudgeon pin, brg and small end of connecting rod. Percentage ? Less than 50% for a 2 stroke. There's no exact number.

8mm change on piston diameter - you'd think that would weigh more, assuming piston design is same in both, they might have put big one on a diet ?

 

 

 

 

Dyno owner Joe Harkness and myself had long conversations about cut times vs dyno, its very consistent. There's small room of error when b&c combo and sharpness vary. Its a decent way to measure power increment.

 

You could be right about piston weight being trimmed on the big ones, i have NOS 090 top end. Will weigh em when im free one of this days

[Brill]

Husky are replacing the 395 so 595 mabie think it’s out 2021 in feb perhaps 

[Stubby]

29 minutes ago, Brill said:

Husky are replacing the 395 so 595 mabie think it’s out 2021 in feb perhaps 

That has put the value of my 395 up a bit me thinks ?

[Moose McAlpine]

1 hour ago, Stubby said:

That has put the value of my 395 up a bit me thinks ?

 

Sell it to me, i don't have enough.