I know these are noisy but...
 

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..

If you do a search on Youtube for XT's you will be able to hear a few of them in action, which may or may not put your mind at rest.
:mchappy:

Best of luck

When replacing the piston did you change the gudgeon pin? Does the sounds decrease a bit as the engine warms up? Is the cam chain tensioner working correctly? The cam chain does make quite a noise. A constant whirring drone. It is a bit off putting at first.

The cam chain tensioner seems to be working the way it should. I've taken it out, reassembled it etc. The cam chain and piston pin are new. It does seem to settle a bit when it gets hot but could be hearing loss from my exhaust..
As an aside, I've taken it to my local friendly mechanic who mentioned float adjustment -> carbon buildup -> hard starting, but wasn't overly concerned about it exploding.
There was also mention of worn cam lobes/ shaft that would make a lot of noise. Short of replacing those parts I cant see how to get past that. The whirring sounds are quite unnerving though.

It's unlikely that the cam shaft itself has worn faster than the cradle. It's a true fit without bearings, white metal or not. Remove the timing plug that covers the camshaft sprocket timing marks (LHS Head)and see if you can detect any free play in the cam. Unlike the Honda XR's this isn't a particularly vulnerable part of the bike thanks to the XT not having that ridiculous tea strainer for an oil filter, so I doubt it's that. What I can say is that in all the incarnations of the aircooled, dry sump XT an TT variants that I have owned, they all make a disconcerting whirring emmanating from the chamber in which the cam chain ran. If there was fault...it never slowed me down and I put on plenty miles.

I asked about the gudgion pin as sometimes these are not replaced with the piston if done on the cheap (well when I was a student leastways...:-) ). Big end knock on these bikes when cold is something terrible to hear but quickly dissapates into something more gentle when the engine gets to running temperature.

The usual advice for this engine is to use no throttle when starting - don't even touch the righthand grip was my technique to break my automatic tendency to turn the throttle while starting (on a kicker TT600R).
I wouldn't worry about cleaning/adjusting the carbs when you get around to it: straight forward I reckon after the work that you have done already getting into the inwards of the engine.

The noise:
As well as Youtube, try to find someone else around your area who is running an XT600 and compare the levels of noise.

Are you running in the engine since the rebuild?

You could removed the oil filter and drain the oil and check for metal debris. If there is none, you probably dont have as big a problem.

Steve