Pt.2 - Twin 660 build: Felling Saw's 1st Cuts & Overview

Big bore top-end is detailed in prior video but it's ported&polished cylinder and piston and probably displacing around 102-104cc's at this point. Compression is solid, but have a Hyway popup and Stihl d-handle if I think it wants/needs it after some real break-in!! Cooling system is modified to force all flywheel air onto the top-end only, achieved w/ minor work to the top-cover but primarily via a large aluminum muffler-sized heat shield that sits between muffler//cylinder, instead of those lil OEM muffler gaskets, works both to guide the flywheel's cooling air exclusively to cylinder while simultaneously separating the muffler's heat from the rest of the saw! Timing is advanced ~10thou off key, gearing is advanced 8T rim sprocket.
Full wrap bars, XL 'skeletonized' dogs, 25" Rollomatic w/ RS33, full vertical&horizontal felling sights, elasto-clone starter w/ 4.2mm nylon cord, permanently affixed blue tachometer. Airbox is 100.0% filtered meaning no pre-filters on the air filter, and a high-flow sponging material as carb-spitback "plate". Muffler actually scavenges & provides some back-pressure (still moderately high-flow, I think most - mistakenly - think way too much muff flow is good, not knowing it's very easy/common to go too-far here!)
Will update after more time spent with him IE tuning, altering/tinkering and testing so probably a few weeks, I want to try at least 1 more timing-setting, and will be testing a "different approach" big bore top-end soon on this one as well (and, if it beats the 54mm bucking saw, then that saw will also go big-bore!)

[@joescissorhands141]

Update: Details are in Pt.1's Comments but the big bore porting was too much it's spewing some charge at TDC (high pressure spray, never seen it before), uncertain if it's too-wide exhaust port (my suspicion) or a touch of freeport but will address them both on the untouched cylinder, will still be taking this unit to a job on Thur to feel it out because it's still feels right enough despite a bit of oil on the muff that I'd rather not see, but the compression can be bumped so the Hyway pop-up is going in (with Stihl D-handle) and the new jug will be "tight" @TDC so will then have my "real build" done!

[@mattymodeerf]

It certainly cuts fast now, and not as loud as your other one it seems