I have finally posted some
photos of the valves. Note the big size pics are full-size, so warning to those with slow internet connections!
I'll start another thread as well (not meaning to crosspost but this is just the project thread) with some questions but I have a big one:
were the F2/F3 valves supposed to have a bevel at the top end? (See
intake stems and
closeup,
exhaust stems and
closeup.)
If not, how much can I safely remove to square them up before the valve's too short? There's no "minimum valve length" specs I can find published, and Hondaman's book suggests no more than "just a little bit." Overall the shaft diameters seem to measure fine for wear, and the seats seem reasonable (so far...). If the tops aren't destroyed I will probably go with these, lap the valves, install a new set of guides and maybe retainers, run the engine for 10-20k miles then check them again.
I also started cleaning the pistons. Turns out soaking them face down in a mix of brake cleaner and Seafoam worked wonders. I ended up using brass brushes, a small flat screwdriver to clean out the "exhaust-facing dot", some very fine steel wool and some P800 emery cloth to get the worst stuck-on residue off. (Yes, I'll make damn sure there's no steel wool bits lying about before reassembly, especially in the ring lands!)
I don't have a photo (yet, batteries died on camera yesterday) but under all that carbon, the piston faces are grooved with many concentric circles. My instinct tells me that this is original factory lathing used to cut the domed profile. My instinct also suggests that it would be a fairly good idea to remove those ridges with some sandpaper.
Good idea / bad idea? It seems to me that grooving promotes carbon deposits which in turn promotes pre-ignition... Regardless, I ended up removing some of the face concentric rings off of piston #3 already in the process of cleaning it, so I guess I'll find out.
So far bore-to-piston clearances are at 0.02-0.025mm; we'll see if after honing it's still low enough for me to seal with good oil rings. The chrome rings are tolerably OK (0.45mm gap avg) but not the oil rings - gap is showing greater than the largest feeler on my gauge (> 0.83mm!) One of the upper chrome rings also snapped on removal, so I guess I'll be getting a whole new set anyway.
I disassembled my busted spark gap advancer and found the inner shaft to be worn flat in many places. I guess it's good that I got a "new" one from a late-model K! I've disassembled it too, taken careful measurements of both, and will be posting a thread with my observations. Very interesting stuff!
I got most of the easy-to-access cylinder head surfaces clean with oven cleaner, elbow grease and "non-stick-safe ScotchBrite pads," but it's still not clean enough for my tastes. And then there's all the scuffed paint to deal with! So, the rest of the weekend was spent building a sandblasting enclosure out of scrap wood (thanks, doozer!). It'll be perfect for beadblasting the engine head / cases to prep for painting -- or will I powdercoat...hrm...
I'll edit this post with a few more pics and links to other threads once the batteries recharge.
Next up: Photos of the sandblasting enclosure (about 24x24x36, breaks down for easy storage), cylinder honing, more detailed measurement summaries, blasting before/after pics, and gettin' into the crankcase guts (finally!)
