Really happy with the performance of my new GS Aero trike, but not happy with the excessive noise from the drivetrain, especially when power is applied to the pedals. Initially, thought the source of the noise was un-belled chaintube ends. Belled the chain entry ends and relocated the return tube, but the noise was still there. So, that left the stock, dual, toothed idlers as the noise source. After replacing the dual idler assembly with a non-toothed, single idler, problem was solved. The replacement is a worn out toothed idler I turned down in my lathe to remove what was left of its plastic teeth. Machined a "V" groove in its center, installed an Ace Hardware "O" ring in the groove, and pressed in dual 608zz ball bearings. Now riding in silence, as long as I'm pedaling. Freehub is noisy as all get out, while coasting - would have to replace the hub to solve that problem. I hate toothed idlers - they're all noisy, even the plastic-toothed ones, like the stock ones on my Aero. Mashers that are capable of high power outputs probably need metal-toothed power idlers on their recumbents, but not a moderate power output spinner, like me.
 
 

 
Speedy little red devil.  
 
 

 
Stock idler and chaintube configuration.
 
 

 
Chain entry ends of chaintubes belled and return tube relocated.
 
 

 
Dual toothed idler assy. replaced with single idler with rubber "O" ring in center.  Return chaintube relocated to under
chainkeeper and parallel to power side chain.