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Well it certainly wasn't the leading problem.  I was thinking about this possibility last week and rode home one day with my foot under the pedal the whole way... didn't make any difference, the brake was still locked up enough that it was very difficult to pull the bike back against the curb when I got here.  However I already had my eye on swapping the master cylinder so I took a close look at the parts when I pulled it all apart this weekend and that pretty much confirmed in my mind that there was indeed supposed to be a spring there.  It could very well be that one problem exacerbated the other.

Oh well, the current leak will either resolve itself or I'll tear down and clean up the original master cylinder, and I'll probably run over tomorrow to grab a stiffer spring for the pedal.  And with the fiasco around the front forks earlier this year, the new pair have been riding smoothly and not leaking a drop of oil so I was able to replace the front brake pads with a new, clean set.  Still not sure what to do about the valve cover oil leak without tearing down the engine, but I may go for that soon anyway because when I put the engine back together I tried re-using the old rings, and I'm feeling like that might be the cause of it being so difficult to start after sitting for a few days.

One thing that's still bugging me though is that sound sort of like a chain rubbing the front of the engine.  I *think* it's an exhaust tick despite using new copper washers, but I'm not really sure if there's an easy way to confirm that theory, or even to tell which cylinder might be leaking?  I dunno, but at least it's running.

Is the flexible hose new? If not, it could be contributing to the problem. It is not very common, but it is possible that the flexible line is nearly blocked with crud, or it could be delaminating inside and the loose part can act like a one way valve. If the flex lines are old, they should be replaced anyway, else one may burst when you need it most.
A valve cover leak does not require an engine tear down unless the gasket surface on the head is so badly damaged it need machining. The cam cover gasket and the end plugs can be replaced by removing only the cam cover. Taking it off will also give you a chance to inspect the valve train for anything that might be making the sound you mentioned.
To determine if it is an exhaust gasket, you can take a length of hose (two or three feet, any diameter) and use it like a physician’s stethoscope. If you are still suspecting one of the exhaust gaskets, be sure that all the nuts are properly torqued. DO NOT OVER TIGHTEN THEM! The studs are easy to break. If that does not solve the problem, and you are certain one of the gaskets is the culprit, then pull the pipes off and carefully inspect for an old, black, crusty gasket stuck in the port. They can be really difficult to see. If you do not find any old ones in place, you may want to replace them all with Suzuki (GS1000, as I recall) gaskets, which are thicker.

@TexasKZ -- The main brake line between the master cylinder and caliper was replaced this Spring.  I never saw anything about replacing the line from the reservoir?

So this bike was a 100% tear-down of parts from two other bikes, plus various bits from ebay.  All of the external engine components were cleaned by hand and then sandblasted so I can assure you there was no remaining gasket material stuck to the head.

I've heard of people resorting to permatex on the head due to never being able to get gaskets to seal.  I installed a full-engine gasket set when I reassembled the engine, and I did visually inspect each surface as I stuck them back together.  Gaskets were painted with the sticky brown stuff.  Torqued all the bolts, ran for about 100 miles and torqued again, then checked once more at the 500-mile oil change.  I've recently checked the outer ones by hand but haven't pulled to tank to properly check torque.  I'm hoping to do that when I get around to rebalancing the carbs.

As for the exhaust... I did recheck torque around 100 miles.  Both the oil leaks and the buzzing sound were present within that period (although I did greatly improve the oil leak).  I had assumed that if the sound were coming from the timing chain, then I would have seen metal floating in the oil at the 500-mile change, but it was clean.  Someone suggested to me awhile back that the exhaust could also make that sound.  I used to find intake leaks on my old car with a can of starter fluid, but I can't think of anything like that which would work on the exhaust to show leaks.

This is the spring I was talking about. 
Steve
 

Oh yeah, mine doesn't have anything like that, it just has things like line up for an inline spring.  What year is your bike?

Not mine it's a 79 on KZMarket $4200.
Steve
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The J-engined 1000 LTDs (1981 - 1982) have a completely different rear brake pedal, bracket and master cylinder setup than the earlier LTDs.

Here is a picture from the factory service manual. In the upper left you can see part of the pedal return spring. 

 

Here is a view of the pretty side as mounted. The brake pedal, master cylinder, passenger peg and the muffler bracket all mount on this aluminum casting, and there is no coiled spring around the pedal pivot.

 

@TexasKZ yeah that's the style I have.  All these years I didn't even realize the height of the brake pedal could be adjusted until I swapped the master cylinder last week and couldn't even sit with my foot on the pedal because the brake was so high.  I took it apart again and screwed everything down all the way, and the brake pedal is finally down in a comfortable position where my foot doesn't rest on it.

Still haven't made it back to the hardware store to try and find a heavier spring though.  At this rate I should just grab something off ebay.

The cam chain could be making noise without leaving any metal in the oil. It could be slapping against one of the rubbing blocks. The tensioner could be faulty or the chain may be stretched beyond the tensioner’s limits. Could be both, I suppose. There is also a chance that one of the rubbing blocks has broken. They do get brittle with age.

Ha! Glad you discovered the adjuster, it does make riding more enjoyable.

I had parts from two engines to pick from when I put everything back together.  The plastic tension block I picked didn't show any sign of wear, and it didn't appear that the chain was stretched very much -- I can screw in the tensioner until it's pulling the chain tight, with plenty of room to go further, so I assumed everything was still within spec.  I did check and readjust the tension when I first started hearing the noise but it didn't make any difference.  Couldn't hurt to pull the cap and recheck the indicator though.  Guess there's not really a way to check for broken bits without pulling the head.