I decided a year ago to resurrect my slightly dead and very seized 83 XT600 (1000km ride then broken oil pump then a long trip on a truck). I've not rebuilt a bike before and the reasons for the rebuild were probably a little loopy.

So far most of the bike has been replaced (all bearings, piston etc, rebore, oil seals, O rings, valves seated, OIL PUMP, cam chain etc. New renthal bars, indicators, tyres, chain & sprockets, all cables and most of the wiring and.. a bunch of bits i couldn't find I think thats about it. Anyway... I bought the clymer manual and some tools.. (and had some good advice and thanks to this forum) it goes again. With much noise. Basically not much of it was not broken in some way. Actually I cant think of anything right now.
The exhaust is worse than a straight tube (large bits of metal fell out when I removed it, so there is that.) and thats next on the list, but thats no problem.
I blew a head gasket so I rechecked the torque settings, slapped myself, checked ALL the settings and replaced the gasket. I did find a lot of carbon on the piston crown etc. Setting the valve clearances was quite an education but I'm reasonably confident its right. A few important bits I've not gotten to yet; suspension seems ok, frame/ tank/ brakes (replaced pads/ shoes), carbs. Dealing with the carbs is obviously next as I'm a bit nervous about going there but will.
Anyway.. I could, and should take up most of this in other threads..
The increase in power is, well, what you might imagine. I've not ridden it much as theres more to be done. And needs to be run in properly.
Did I mention its noisy? I'm ignoring the exhaust noise for now... I know these things are loud and describing a sound is awkward at best.. theres a lot of noise from the head, cam, top end.. tappets sound ok I think. (I can hear it but its not deafening - unlike my 1st attempt) I guess what Im getting at is that it sounds like a very noisy engine. Noisier than before I started doing all of this.
Are you supposed to be able to hear what the internals are doing? and how clearly? Nothing sounds 'wrong', no banging, knocking pinging. Things spinning very loudly. Not grinding but metal on metal (obviously), controlled explosions at regular intervals.
I know this is very vague, I'm getting nervous though. One more engine seizure on a freeway might cause a seizure in me I think.
Theres oil pressure (undo bolt above filter, oil squirts out) no major leaks. It starts first kick with choke when cold, can be a s**t to start when hot (no choke and tiny throttle) and stalls sometimes, again need to look at carbs. It has 45000km on the clock which might not be true, I've had it for 2yrs and no idea of its history. This is the only work I've done on this bike and have little previous experience with engines. Plenty with machines of various descriptions but this is new to me.
What does a normal aged XT600 sound like?
Apologies the long post, I could probably write a book about rebuilding a largish bike in a bedroom..