Thanks for all the advice and explanations so far!  The animation did help visualize hydrolock, just thinking about it is  .  Poor engine.

I went out and tried Scratch's trick, and here are the results: there does not seem to be a difference between the left and right sides.  The stroke seems to be almost exactly 3" (plus or minus 1/16"), as shown in the following 2 pictures.  I repeated the measurements twice, the first time was with me sitting on the bike and rolling it back and forth in 6th gear, the second was with the bike on the centerstand and rotating the rear wheel manually:

White background:


Black background:


Here's how I did it (other newbies might find this helpful).  I used wooden skewers from the local grocery store, and made marks with a Sharpie at the top and bottom of the stroke:





Left spark plug:




Left spark plug comparison with a new spark plug:


Right spark plug:




Right spark plug comparison with a new spark plug:



One other thing I noticed is that my chain is too loose and needs to be adjusted.  I don't think this would cause noise with the bike stationary though... (?)

Sooooooo, these results suggest that it might not be a bent rod?  What do you guys think?   

Scratch, I just sent ya a PM... 

i had a simular sound on my cbr, the stator bolts had backed out after 11 years, and = bad things. new stator, flywheel and cover. i would pull both side covers off and check. if nothing wrong all you need is a new gasket for the left engine cover.

The clunk you heard when you started your bike cold has to do with the sprag gear that drives the pump. Starwalt has more experience in its function, but when its cold and the gear is worn then it jumps out to engage the gear train combo that the pump is on, but the force of the thick viscous oil makes it really hard to engage and it slips of the teeth and goes back in, that is the clunk, at least that is what someone here described a while back. Let me do a search

How is your chain Tensioner?
Does the sound disapear after getting up to higher speeds?

Here is a link to pictures of what is under your LH crankcase cover, something might have come loose in there

http://home.bellsouth.net/p/s/community.dll?ep=331&folderid=180855&groupid=41309&folderview=thumbs&ck=

sounds like a harley 

Quote from: mike_mike on June 20, 2006, 07:55:23 PM
sounds like a harley 

Hey.  Stop picking on my GS.   

Quote from: Catcams on June 20, 2006, 06:48:59 PM
How is your chain Tensioner?
Does the sound disapear after getting up to higher speeds?

The chain is a bit loose and needs tightening, I verified this yesterday while checking for a bent rod.  I need to fix it, but that wouldn't cause any noise when the bike isn't moving would it?

Quote from: rangerbrown on June 20, 2006, 04:25:26 PM
i had a simular sound on my cbr, the stator bolts had backed out after 11 years, and = bad things. new stator, flywheel and cover. i would pull both side covers off and check. if nothing wrong all you need is a new gasket for the left engine cover.

Quote from: coll0412 on June 20, 2006, 06:53:19 PM
Here is a link to pictures of what is under your LH crankcase cover, something might have come loose in there

http://home.bellsouth.net/p/s/community.dll?ep=331&folderid=180855&groupid=41309&folderview=thumbs&ck=

Hmmm, I see... so it seems like I might be able to have a look if I remove the crankcase covers, starting with the left one then?  Stoopid noob question: do I need to empty the oil from my engine before I do that?  I do, don't I...  Actually I should look it up on my Clymer (I have a Haynes coming in real soon btw, it's been highly recommended).

tough problem! i have a question for the experienced engine gurus: if a connecting rod is bent, how much of a difference between the cylinders would be observed? would the kabob skewers as shown in the pictures be able to detect the difference, if it was small enough? i mean, if you're trying to find a difference of 1/32" with sharpies and rulers it may not work out so well. can the the depth-gauge part of a dial caliper fit into the spark plug holes? this may give you a measurement accurate to within 0.005-0.010" or so.

i guess you'd have to be careful not to scratch the pistons with the metal caliper. how bad would it be if you did scratch the piston?

i would drain the oil, but save it and check of any thing that shouldn't be there. (metal)



the rod's, if they were bent it would show in as little as  1/16 in or more, till it snaps any way.
but remeber, there could be corbon build up that is in dif thickness that could throw it off.  but if it were bent you would know it very, very shortl after happening, as it throws the balance off.

Quote from: che mike on June 21, 2006, 12:04:59 PMi guess you'd have to be careful not to scratch the pistons with the metal caliper. how bad would it be if you did scratch the piston?

i wouldn't matter at all if you scratched the piston, chances are that covered in a layer of carbon any way.

the chain being loose wouldn't matter when your not moving, it defently wouldn't make the noice your sick bike is making.
the stator side is dry so you could check that side first and check that none of the bolts have come undone and are getting knocked around by it,
good luck

Okay, so just to be sure, if I remove the left-hand crankcase cover where the stator is there should be no oil in there?  So I can do it without draining the oil from the engine, correct?

EDIT: btw, my friend and I seem to have narrowed it down to the left crankcase cover region.  If you put your hand on it you can actually feel a tapping of sorts that coincides with the noise.  Also when I heard the *clunk* at startup it was coming from the bottom left, I'm pretty sure.  Weird stuff though, because if you get your ear close to the engine on the left side, you can hear it coming from the bottom, but if you do it on the right side, it would seem to be coming from the top.  But I guess that's just the way the engine resonates or something.   

left engine cover will have oil in it, right engine cover should not.

Okay that makes sense.  Why else would it have a gasket on it right?  duh.   

So the alternator is actually submerged in oil then?  Huh, I never realized that.

yep as it is the starter gear on it as well.+ it keeps it cool or cooler thatn free air.

Well, I listened to it last night, and first I rotated it over cold, just listening and feeling as I turned the crank.  As I turned it. with the plugs out, I still got resistance (from the cams no doubt), but in certain areas of the rotation it felt like grinding.
Then we started it, ooohhh, did it not sound good.  It started great, started right up, but at low rpm it made a loud rotating deep clunk-a-clunk sound; definitely from the left side.  Now, looking at the oil on the dipstick it looked fine, there didn't seem to be any particles in the oil, so I didn't think that it was bearings, but the sound does.  When it's revved up, the clunking goes away---oil pressure must be floating whatever bearing (be it the crank or balancer).

I suggested the oil drained and the left cover removed for further investigation.

I will be calling shops in the area.

Thanks again for stopping by scratch! 

When he heard the low-rpm noise I thought scratch was going to have a heart attack right there.     He was like "OOOOHHH  OOOOOOHHHH, THAT DOESN'T SOUND GOOD.  KILL IT!  KILL IT!" *gets exorcism started*     (well, maybe I exaggerate a little, but you get the point). 

So as much as I'd like to get my hopes up, everything seems to point to a bad bearing.  Still, I'll take out the left cover this weekend and have a peek in there.   

Quote from: WildBlue on June 19, 2006, 09:34:11 PM
Well, I'm getting the good ol' GS back on the streets after ~3 months of inactivity.  She's running well, except for a very annoying rattling noiose coming from the lower part of the engine it seems.  The noise is there with the engine idling, and is loudest when I'm accelerating from a stop.  It seems to disappear above ~3-4000 rpm, but it's possible that it just changes frequency and I can't hear it.  Here are three short videos I took today while trying to identify the origin of the noise:

Right side of the engine

Left side of the engine

Riding around the parking lot

Am I in urgent need of a valve adjustment?  btw, I'm at 12,400 miles (had it for the past ~3000 miles).

Thanks for the help!   

This is a classic example of a question you shouldn't be asking ... the answer always is ... yes ... its easy and bloody well eliminates so much guesswork.
So it does need it ... BTW I didn't click your links ...
Cool.
Srinath.

A valve adjustment is the least of his worries at this point.

I talked to Greg @ Santa Clara Cycle Accessories, they don't do engine teardowns, and he suggested Double R Cycles.  Ph# 241-9850  We conjectured that maybe the generator is coming loose off the end of the crank and is wobbling around. 

I'll be looking up where RR Cycles is located (or I'll call).

Edit: Although, twice now has two people stated that it might be valves (valve adjustment)...I'm just thinking if it is at all possible for mal-adjusted valves to allow, or make that noise?  Srinath?

your videos made me curl into a ball and cry.