I'm lovin that superimposed CAD drawing.  Really shows the difference between the 3 angle and 5 angle.  I really wish I had your IT skills.  Being able to whip those CAD drawings up is really beneficial.  Nice job.

Zevengerie, if I understand correctly, you are suggesting a 35 to 38 degree back cut on the valve rather than a 30 degree.  That's a good suggestion.  You could do the 35 degree back cut and then flow test, then do a 30 degree backcut and compare the data.  I can see how the 35 degree might direct the flow in a more advantageous trajectory.  My Gizmatic only has the ability to cut 30 degrees, maybe a little lathe work on old junk valves is in order.

"I am considering fitting new seats, to advance the valves one millimeter into the combustion chamber"

Finn, I would reconsider this idea.  The flat-top pistons are already running compression ratios on the ragged edge of detonation.  Although I have not encountered any issues with the 94mm pistons, I am having some detonation problems with the 97mm pistons.  That makes sense since the 97mm pistons inherently drive up the compression ratio.  As I recall, you are running a 94mm.  If you make those valves proud in the combustion chamber you will most likely tip the CR over the edge.  I am finding that you can't massage the combustion chamber more than about 1cc.  That's not enough to mitigate the problem.  When I originally came up with the flat-top idea, I asked for a 10cc trench cut in the top of the piston.  That would have resulted in a CR around 10:1.  Instead, Wiseco did a simple radiused dish in the piston top.  That only provided 5.2 cc of additional volume.  The CR on the 94mm is up around 10.8:1.  It seems to work but it's right on the ragged edge.  The 97mm flat tops are up around 11.4:1.  I think that's too high.

When you go to those 35mm valves, I think you should be thinking about adding a little more combustion chamber volume.  Try to get the CR down to 10.5:1 or less.  Setting your valves proud may seem like a good idea for flow but it's gonna reduce your combustion chamber volume.  Don't overlook the fact that the improved flow is gonna increase the dynamic CR.  You want your combustion chamber at least 55cc, but 56 or 57 would be better.  If you want to really trick it out, trench cut your piston and get the CR down to a more reasonable 10:1.  It's carbureted with no engine management system (no vacuum retard, no knock sensor, no fuel enrichment, etc.).  It's right on the precipice of detonation.

Wow... what a great idea those aluminum lapping tools on a standard Neway pilot. I'm going to shamelessly borrow (steal) the idea from you Mike.

I've been hesitating for a while about the price of the newway cutters.
I've had a look and there is also diamond sandpaper that lasts about 15x longer.
Maybe it's possible to do the whole valve job with these tools.
It wouldn't be too difficult to make them electrically powered.

And then invest in a hone or a Valve guide reamer so I can fit new valve guides. Because I think that egg shape could be amplified by wear of the valve guide.

I also want to say that I am impressed with that cad drawing. It makes it much clearer.

Thanks for the inspiration. You guys are very skillful.

I found this video very inspiring:

https://www.youtube.com/watch?v=VsLaRlDAMF8

He uses a bearing. It's not that hard to use that principle for a simple strong back/hold.

You install the strongback assembly in the adjacent valve guide.  For instance, if you want to cut the right-hand exhaust valve seat, you install the strongback in the left-hand exhaust valve guide.  Then you set up the cutter pilot and cutter, and install a special driver on to the cutter.  The driver includes a socket assembly along with a wrench with a ratchet feature.

Finn, your flywheel idea sounds very promising.  My experience with the Neway T-Handle driver has been less than gratifying.  Lots of chatter, uneven cuts, poor finish, etc..  It's just too hard to maintain uniform pressure while turning the T-handle.  A heavy flywheel might be just what the doctor ordered.  It would smooth out the rotating force and provide an absolute uniform cutting pressure.  Great idea.

Regarding octane, I think you guys in Europe use Motor Research octane(DBM 7/2/24) while us guys in the States use R+M/2.  So, my 92 octane should be equivalent to your 96.  That 100 octane stuff you have available at the local Shell station would be like a 96 octane here.  Alas, I can only dream of 96 octane pump gas.  Who knows. you might be OK with the 100 octane Euro Gas.  All's I can tell you is that on 92 octane R+M/2 pump juice here in Hawaii, the 97mm pistons start experiencing detonation issues.  My 94mm pistons (stock, Wiseco Pop Top, & Wiseco Flat Top) all did fine.  No detonation on the 94mm pistons in any configuartion that I tried.  But the 97mm pistons seem to have a detonation issue.  The 97mm pop-top works fine with a stock cylinder height, but if you deck the cylinder to increase the compression ratio, it seems to detonate.  The 97mm flat-top already has big-league compression and it also seems to detonate.  I am working on a report.

I suggest you stay away from anything that reduces combustion chamber volume.  Shoot for 56 to 57 cc combustion chamber volume.   If you are worried about valve shrouding, grind the offending material away from the area around the seats. Don't try to make the seats proud in order to unshroud the valves.

If you decide to replace seats you might consider doing as the late Kenny Augustine (dba Kinetic Analysis, he did the heads on the Butler & Smith BMW Superbikes back in the day and was a well-known porting specialist) did on occasion.  He'd make the seat very deep (compared to stock) and of a smaller ID when he wanted to shrink the ID of the port above the seat.  Instead of trying to weld or use an epoxy filler in that area, he'd add the extra metal in the bronze seat.  That could also have IDs/tapers installed in the new seat  above the valve seat area before it was inserted into the head rather than having to grind them by hand.

Kenny was quite willing to saw a head into pieces to get access to areas where he wanted to weld in more metal and then weld it back together and remachine everything.  Some of the heads looked rather different, as I can remember Aermacchi and BSA Gold Star heads where the valve angles were narrowed and the rockers raised to allow longer valve stems so the port could be straightened.  He'd also do some frame work, such as this article on "the world's straightest Commando" in the Internet Archive:

https://web.archive.org/web/20091214231054/http://www.vintagenet.us/phantom/w...

Kenny was quite an interesting guy, it is too bad that his heart took him out in his late 60s.

Nothing is too good for my savage, and today arrived treasure!