Stihl 400 vs. 661 - Medium (32") Bar Palaver

Filmed in May, 2022.
April & May were quite busy in the shop and woodlot. Back and forth with the alter this, test, alter that test. R&D, for me anyway, is a time consuming process.
I had done a few 400s that were over-lapping in the Custom Saw Modifications process. Attempting to figuring out what a Mag piston would handle. Reason being, Magnesium is a very soft metal.
Now add in the coating the piston has. There is a lot speculation it is ceramic. The motorcycle industry seems to be using a ceramic and/or ceramic composite coating so it makes sense. However, I've talked to several Stihl Tech Personnel fairly high up in the food chain. They can "neither confirm or deny" the actual material composition - because they are uncertain at this point themselves. So, I wait...
Some specifications -
The 661 has a hp rating of 7.2
The 400, same factory, has a rating of 5.4 hp.
That's a 1.8hp differential. Stock for stock.
Completely different way the hp is derived - The 400 is a "Mouse Motor" High Winder. The 661 is a Rat Motor with a much lower upper rpm threshold.
Engine configuration -
56mm bore x 37mm stroke in the 661 for 91.13cc. 50mm bore x 34mm stroke for 66.76cc in the 400 . That is a 24.37cc difference.
But, the 400 weighs a whooping 3.8 pounds less than the 661. Every saw has it's place.
The 661 is bone stock. The 400 is at the Psy-Ko S level zippkit wise with my "Patented" "Torque Tweak" add into the mix.
What we watched here - A MicroHowler sized saw not getting embarrassed by a "big kid" saw that is 3 models higher in the line up while sporting a 32" bar & chain
Looking at the timed runs -
ms400R c-m at 14,040 rpms ran 32.11 down 35.18 up, 35.90 up with am #1 air filter test subject.
ms661R at 13,380 wot went 28.60 down and 32.20 up.
ms400R c-m at 14,040 rpms wot with am air filter #4 ran 36.75 up and 36.92 down.
Important to note - the diameter of the cut increased by at least an inch for the second session with the 400. WITH the addition of some pretty impressive knot interference. I've been liking the am #4 filter option.
In the end, the 400 didn't win against the 661. The smog saws are not designed to make power. They are engineered to run hot, burn clean, and not emit excessive hydrocarbons into the atmosphere.
Overall, I'm impressed with the performance of this 400.
At the time of your viewing this, I may, or may not, be immediately available for custom saw modifications. I am booked out several months regularly. If you are interested in having a saw zipped, please shoot me an email. That is the best, first point of contact.
[email protected]
Thanks for watching.