I have a detailed update, first off let me start by saying im a certified master mechanic of about 45 years now, lot's of foreign early on then settled with mostly Japanese for the last 30 or so years...
I bought a spare first gen so the pressure was off in tearing into my original one and worrying about having my only car disassembled and not being able to drive anywhere.
Still was looking forward to doing a proper rebuild and as everyone knows was blindsided by a couple of sites saying the parts were available (OEM) and not being able to get them after I ordered,,,
hence the reason for this OP...
Ok - read allot of the replies and thanks for contributing, here's what I have to offer in the form of all my experience with engines and iv rebuilt hundreds, I like these little 3cyl. allot, they are little jewels inside,
I will say that in all the engines iv gone into in the past iv never seen connecting rod bearings hold up so well,
150,000 miles and they did indeed look like at their wear rate they could go a half a million easy if treated with good oil,
I did not even pull down the main bearing rack, when you see rod bearings holding up this well it's almost a given that the larger mains all running in line with each other will be in even better condition,,, plus I cannot get parts anyways.
now that iv gave credits to the lower end I have to comment about the upper end meaning pistons on up, these engines suffer badly and in fact even worse than typical japanese engines due to the lean burn and heat they have to deal with in the combustion end and the parts associated, (manual tranny)
I pulled mine down in the first place due to piston slap and knowing it was a little "loose" and clapped out, and indeed the piston to bore specs were just out of range by about .001" to .0015",
but part of the reason for this happening is that ALL the oil rings were frozen solid, they were gunked out bad - this is quite common in higher mileage engines but this was an extreme case, in fact --- all 4 oil ports in the piston that feed the oil rings (12 total) were completely shut with carbon, this sets the seen for a slow death, lots of people think oil rings jobs are to wipe oil away - not so - oil rings are better looked at as "oil distribution rings" it is the secondary ring that is also called "the scraper" and in fact has an undercut bevel to do just that - that has the last say on how much oil gets past the upper ring...
so - the piston was running dry, and you could see it on the power stroke side, the side that gets loaded esp. half way down the bore when the rod angle is extreme,,, in fact all my pistons had major "scuffing" on this side and it's where the wear was concentrated...
the nice surprise is once I free'd up the rings and unclogged the ports the pistons are bathed in oil and the oil provides a little extra cushion upon start ups, this does help in the piston slap department so nice change - I also drastically increased the longevity of this engine in doing so, I had to re-use the rings but their end gap was just at the ragged edge of what honda allows for re-assembly - actually slightly over on some but only by about .002"
Ok - now for the head, again --- these engines will go some miles but im not seeing them doing very well in the piston/ring or valve to seat department - major pitting esp. on all exhaust valves, to the point where they will develop sealing problems eventually - again this is inherent to these little guys as they do run toasty, actually have high compression ratio's and the leanest mix going,,, (again manual tranny) there is simply nothing you can do about this - does not matter what kinda oil you run - these parts WILL SEE extreme heat and wear due to what their up against...
there is actually one thing I can say that will help this situation --- keep your EGR system as clean as possible --- it's designed to cut down the heat of the combustion temps (for the cat to pump out less nOx emmisions)
if you do this - you will also reap the rewards of a longer valve train life,,, there's another added bennie, the oxygen sensors will live longer, esp. that expensive upstream one...
anyways - at least you can still get head gaskets and valve guide seals, I do have piece of mind now and know she's got another 150,000 in her, and then another tear down to freshen the head and replace the rings, and Dougs last post I believe is where its at --- there are motorcycle models that share the same bore size and iv checked and at least for the two top rings they share the same thickness ( 1mm top and 1.2mm second) this was for the suzuki gn 250 I believe, might just go into the other engine (that also has piston slap and 200,000 miles) and re-do it and im sure the rings are worn even more --- could be a good test rig to prove the modification of installing the motorcycle rings...
if I do this - I will post on it and the results...
well - hope this helps, any questions lemmie know...