Rapping Noise? 82 Suzuki GS1100E

[Red Rocket GS1100]

I get a rapping noise when pulling out in 1st gear and then again for a little in Second. It seems to come from underneath the bike. It's hard to isolate as it only happens in gear while pulling out.

The background is that it is an '82 Suzuki GS1100E
Its got about 19000 miles on it.

I checked for loose parts. I suspect the chain, but cant be sure. It almost sounds like a loose nut in the oil being blown around by the flow of fluid. I dont even know if that is possible.
Otherwise it seems to run just fine. I have ordered a manual for the bike and it should be in very soon. I just want to make sure that I'm not hurting it in the process by riding it.
Do you all think that it may be the chain? What should I look for?

[KGB]

How loose is the chain?
If you put it in gear while one the center stand, and rock the rear wheel do you hear any noises? Like the front sprocket is loose?

dangerous but you can try this
put the front tire against a wall, bike on center stand, put it in 1/st gear,
release the clutch....you may be able to help pin point the noise

again not advisible very dangerous!

[chef1366]

If it's not a sprocket or chain open up your clutch and take a look.

[hungryman]

I've got money on the chain. If you replace the chain, do the sprockets also.