660 Felling Saw (99/81/125 56mm big-bore, ported-piston, 8T gearing, +3deg ignition, so much more)

[@mattymodeerf]

So awesome its done! Long live big- bores!

[@joescissorhands141]

Seriously! I don't know why 'the scene' (wink wink) has such aversion to this type of build, it should be the most-popular, even Stihl bored their next iteration (ms.661) to 56mm, they under-stroked to 37mm (keeping displacement at 91cc) so if you're not looking to use m-tronic carburetion there's a strong argument you're better-off going with the 660 chassis & putting a 56mm head on it, then going w/ a 661 because there's no simple way to stroke 3mm longer there! The porting of piston & lower-transfers, to accommodate higher flow to the 56mm chamber, inherently add lower-end-displacement to counter-balance the increased top-end-displacement of the 56mm jug, preventing any shift in RPM's for peak-power in your power-band (in fact it over-corrects, if anything, meaning it's pushing peak power to higher RPM -- to be clear that's NOT a higher RPM, just shifting where your peak HP will hit on the RPM range) Will certainly update as I go but I expect I'll be throwing the other big bore kit w/ the Hyway pop-up piston onto my other 660 ('creamsicle' there!) when I care to wrench again, that will be pretty plug&play as it's all already ported so really just need to chamfer, deck & size squish, and install ;D

[@joescissorhands141]

"Transfers are AT 110" = "transfer DURATION is 110deg", realize I misspoke it's not worth re-filming, transfers are opening at 125 giving 26deg of blowdown and having a duration of 110deg total-open-duration! Not a ton, for any cylinder, but not especially small either- and with this jug's exhaust & blowdown, that charge will rush from the transfers w/o impediment and the (lightened/ported) piston swings through BDC & begins suction for intake nice & smoothly before another BANG to begin again, powerstroke to a healthy 99deg opening, and 26deg later begins pumping that cylinder for another go >:)