I have never done any porting myself, but certainly not opposed to it.  Any detailed info on where to remove material?  Just match port to the exhaust, or polish out the entire exhaust track?  I know it's better not to polish the intake to keep the atomization up entering the head.

Once the motor is back in the lean will decrease some (not much).  I would have gone a little less, but what is welded is welded.

The results of my leak down compression test indicated to me that the valve seats could use a recut and the valves reground.  Here are some closer shots.  The adjustable tappets look like they are fine, but the surfaces that ride on the cams are totally shot.  The ends of the valves look good, with no unusual wear patterns or chips.

tappets

This is pretty bad wear in my book.  Going with the newer year hardened ones.

I just finished reading DragBikeMike's Evolution of a hot rod thread series last night.  Very impressed with his approach and documentation of all the research he has done.

Gary - looks like you posted a duplicate link to Mike's cylinder head thread.

I agree Sneeze, your adjusters and valve tips seem to be OK.  I still think you should do a leak test with mineral spirits just to see what you can learn.  It's quick & easy.

As previously mentioned by others, excessive wear of the cam & rocker pads is not uncommon.  Your engine is very old (like 35 years old).  That is why I think you should leak test it, disassemble it, and inspect it.  

IMO, if your valve guides are shot you would be better off finding a good used low-mileage head.  Only way to find that out is take it apart.   Also, if you plan on porting it, disassembly will be mandatory, and you want to finish the ports before any valve seat work.  That way you won't rat-bite a nice freshly cut seat.

If tooling is a problem, check out these el cheapo spring compressors.  If you fish around on Amazon you can actually find them for as little as $16 bucks.  Our LS650 has 30mm spring retainers.

https://www.amazon.com/DASBET-Solid-Spring-Compressor-Service/dp/B074ZHY3WJ/r...

Mr. Gary, muchos mahalos for the link to Mixxer's Thumper Talk post.  Very nice indeed.  Haven't read it all yet but it looks first rate.  Man that 400 has killer valves.  We can only dream about those.  They look like 38s.  Do you happen to know what size they are?

I got the head off.  Cylinder wall looks good.  A light hone would be all it needs, if anything.  Cross hatches still visible all the way down.  They get a little faint in places, but still visible.  I have some denatured alcohol for a leak down on the combustion chamber, but I must have thrown out the old spark plug.  I have to go fetch a new one to seal the combustion chamber to do the leak down.

Not sure I have mentioned this earlier in all of my posts, but the speedo on this bike has logged just under 10k miles.  No way of being certain that is accurate, but the condition of the cylinder wall makes me tend to believe it's a true number. If my local m/c shop is open today I will pick up a spark plug and do the leak down test using some denatured alcohol.  With the leak down compression test showing a 60% loss at 30 psi, I suspect there will be a substantial leak passed the exhaust valves.  This is where the air pressure loss was coming from - out the exhaust port.