Difference between CS 620 and CS621

[Ford3000]

Can anyone tell me what the differences are, I have heard the piston or piston
coating is different, but that's all I heard, other than the 621 got slightly heavier
and lost a bit of power, down to the muffler I suppose.
Asking as the 620 is a 100.00 cheaper where I live, and it has
a track record of being a good saw.

 

[Czed]

@Red97 you know?

 

[Piston Skirt]

Different parts are:
Cylinder (different porting)
Timing map (adjusted to porting)
Piston (ventilated, different coating)
Piston pin, clips (higher thermal durability)
Pin bearing (higher thermal durability)
Rings (different size, coating)
Exhaust (different internal layout)

Although it lost formal bit of peak power it also gained peak torque so in the end nobody can tell the difference.

And the extra weight comes from the same updates the US 590/620 got - metal inserts in starter housing, metric screws.

 

[Red97]

That sums it up way better than I could have.

 

[Piston Skirt]

Addition:
Piston top wall is also reinforced
Also 621 received captive bar nuts, but that was also applied for 620.

 

[Ford3000]

Different parts are:
Cylinder (different porting)
Timing map (adjusted to porting)
Piston (ventilated, different coating)
Piston pin, clips (higher thermal durability)
Pin bearing (higher thermal durability)
Rings (different size, coating)
Exhaust (different internal layout)

Although it lost formal bit of peak power it also gained peak torque so in the end nobody can tell the difference.

And the extra weight comes from the same updates the US 590/620 got - metal inserts in starter housing, metric screws.

So the pin hole in the cylinder is higher up toward the top of the piston, did I get this right.

 

[Piston Skirt]

So the pin hole in the cylinder is higher up toward the top of the piston, did I get this right.

It is at the same spot. The pin metal is treated for higher heat resistance though.
Here’s the pic of both pistons side-by-side.

 

[Ford3000]

It is at the same spot. The pin metal is treated for higher heat resistance though.
Here’s the pic of both pistons side-by-side.

Any images of the difference in the cylinder ports.

 

[Piston Skirt]

Any images of the difference in the cylinder ports.

Not sure if I have them laying around but will look for today.

 

[Duke Thieroff]

Not sure if I have them laying around but will look for today.

Where did you find all the info?

 

[Gullet]

Not the worst design, but I never cared for the wrist pin having washers like the 620 does.
A little more complicated if re-installing (new piston).

 

[Duke Thieroff]

Not the worst design, but I never cared for the wrist pin having washers like the 620 does.
A little more complicated if re-installing (new piston).

Little dabs of grease help with that, a lot