Engine Noise

[Crossrodes]

This bike ('79 R65) has been rattling for some time now.  I don't think it is anything serious like a rod or main bearing since I have not been babying it on the road and I don't think it is the valves...they have been adjusted (twice this summer).  If I can believe what I have been told the bike has about 70,000 km's on the clock (but it's condition when I bought it looked like it had more that this).

I've used a stethescope on the engine and can't locate the source of the rattle.  Are there typical sources of engine noises that I could check on this engine?

[montmil]

The shafts that the rocker arms ride on have been know to loosen up. Even with a valve lash adjustment -the engine is off, of course- the slop in the shaft might not be noticed. There's a stone axe-style fix that's fairly simple to do. Wait for Justin or someone to chime in.

Monte

[willr65]

Pull the clutch in. Does it go quite?  If so it's "geartrain lash".
These are old design engines and will never be quite. However it's quite evident when something is wrong usually.
The rocker assembly is usually the noisiest part of the pre 81 R65.

It's very hard to diagnose without actually hearing the noise.
Do you know anyone that's familiar with airhead engines? they'd know in the blink of an eye!  

[Justin B.]

Depending on how many miles are on the beast it could be the timing chain starting to get noisy.  

[nhmaf]

As other have said, there are "normal" rattles, and there are "other" rattles...
If it sounds like it is coming from the gearbox area, and stops after you pull the clutch lever in, it is probably just "normal" gearbox rattling - many of the gears
in the box are straight cut and with the vibration and spinning of the input shaft, things tend to get noisy.    IF it is definitely coming from the cylinder heads/valve-cover area, then it is valve train related (though the valve system is still "tappy" even under the best of conditions).   if putting a tube to to crankcase to listen and it seems to be coming from the lower/front area ahead of the cylinders, then it could be timing chain/timing gear as Justin mentioned, though unless the bike has alot of miles on it I wouldn't expect that to be in need of attention, unless it was run while low on oil for quite some time.

It it proves to be valve train/cylinder head noise, we can point you to some threads on how to adjust the valves and the blocks that the rocker shafts ride on.
http://suraklyn.com/yabb/YaBB.pl?num=1211995610

[Allred]

With 70,000 miles, or so, I would think stretched timing chain, worn sprockets & guide, and weakened tensioner would be a distinct possibility.   A couple of other symptoms to look for, rough idle, and timing mark jumps around under a strobe light.  

Tough to diagnose a noise in words, but you did say rattle, and that is a good description of the noise my 80,000 mile R100 motor made before changing out the above.  After renewing these parts, not only was the noise gone, but the motor had a more stable idle & lessened vibration characteristics.

Have you checked out tech articles on the airheads site?  Here's one on the subject.  There are more  http://www.airheads.org/content/view/211/98/  

See http://www.airheads.org

[Crossrodes]

Thanks for your input everyone.  I'm leaning more to the timing chain/sprockets being the source.  I'll check the timing to see if it jumps around when I get back in a few weeks.