My 1994 GS500E runs fine, it might need the carbs syncing, but I'm waiting for my vacuum guages to arrive.

However recently it seems to have gotton noisier.
No differences in the type of noise it's making, it's just louder.
I can now notice sound reflecting off walls/cars/bus shelters as I pass them. Any Idea what could cause this?

The valves were last checked about 2K miles ago so I ought to look at them again I suppose. Oil level is fine. Freewheeling doesn't make any noise, so it's not the chain or brakes rubbing.

My thoughts are perhaps knackered exhaust gaskets?

:dunno:

Could be exhaust problem. If it really is a problem, it will get louder and louder. If I were you, I'd keep on riding. The day it becomes really loud, you will easily find the problem   .

Btw., don't forget these are air/oil cooled twins. The tend to make a lot of noise .

I know you posted that you were rebuilding the bike and recall seeing it up on bricks.    I tend to agree with both of you that if the engine wasn't dismantled, then it's likely to be a poorly fitting exhaust connection.

New gaskets and a refitting would be a simple and cheap action.

Yeah I guess I'll see if I can grab some gaskets and do that before I go off on a trip on Saturday.
Hopefully by the time I get back I'll have the tools to synch the carbs.

Yea exhaust leak and oddly intake leaks ... make it noisy as hell and starts sounding sick too ...
Cool.
Srinath.

Well I tracked down the source of the noise.

It's a 1/4 inch hole in the exhaust just after it becomes a single pipe.
My exhaust isn't in the best of condition, but this is a sever and localised patch of corrosion.  My theory is that after my bike was pushed over at the weekend I dripped battery fluid onto my exhaust from the drain pipe
which is missplaced. I'm just glad it wasn;t my frame it ate a hole into.  

Sounds like a good time for some exhaust pipe wrap/patch. Put enough on it and it might look good/intentional.