OK... I'm new here, and new to the fixed gear, thus the question.

I'm running 170 Sugino RD Cranks (48T), a 3/32 17T rear and a 1/8 scram chain on a Steamroller with Velocity hubs laced to Deep V's. When I'm going forward zero sound from the drive, but when I back pedal or put evan a little resistance on my spin it starts to rattle a bit (for lack of better wording regarding the actual sound). Should I hear this? Everything I can think of is tightened up, and the chain is lubed. Also, I get a rattle from the chain when the bike is upsidedown doing maintenance. Chainline is good. And the LBS told me it would NOT be a problem to run a 3/32 cog with a 1/8 chain.

Everything seem to be running fine, I guess I'm just annoyed that my new bike makes this noise, and a little paranoid that something bad will happen while I'm in traffic. Thoughts?

nothing bad will happen. the reason is probably because your chain is bigger than the cog and chainring. 1/8 is a larger chain than 3/32, therefor the sound comes from the slack being picked up from the oversized chain on the smaller teeth. Either way, fixed gear bikes are a bit loud, or at least generate some sort of noise from the drivetrain. The only thing that could be bad is premature wear on the gears due to the oversized chain. 1/8 will work on 3/32 but not vice versa. just get a uniform set and you'll be better off.

My friend broke his 3/32 so I put one of my 1/8's on there and it was like chatter city on that bike. Put a full 1/8 drivetrain on there, you'll be glad you did. Solid and quiet.

You said "rattle", and that's a good description of the normal noise a fixed gear makes. Sometimes they are silent, when the chain is freshly lubed and the tension is just right, and the planets are aligned and the moon is full, the teeth will mesh perfectly with the chain. But, more likely, there will be a small rattle.

Now, if you said "grinding", or "chirping", that would indicate a problem.

New chains can be noisy at first, then quiet down after a few rides.

there is nothing i love more than the ride right after lubing my chain. i feel like a stealthy ninja on a bike...

Cheers, thanks for the help. Maybe if I ever have money agin I'll get a 1/8 cog on the rear.