It does not matter if you have the dual sprocket or the single sprocket in terms of a serious risk factor. The real problem is not just the chain. It's the guide rails. They are made of plastic, and over time they become briddle. The most norious one is the inside guide on the driver's side. Here is what happens: Chain slacks and develops a "slap". "Slap" hits the guide rail described above while traveling up towards the driver's side cam. Guide rail breaks off a chunk. Chunk gets grabbed by chain and turned into the sprocket. Chain jumbs and seizes, pistons hit valves, and the engine bites the dust, as does your wallet.

If you replace the chain only you are still at risk, because the part is still briddle and can break (it has happened, according to a Mercedes shop here in the Washington, D.C. area). If you replaced the guide rails and the chain tensioner and skipped the chain itself, you'd probably be safer than if you replaced the chain alone! (nobody does that, because once you are in there, you might as well do the chain.) Again, this has nothing to do with the number of sprockets.

You can check the guide rails while you check the chain as descibed in the previous post by wbain5280. They are visible right on the front top by the sprockets as you remove the valve covers - plastic thingies the chain rubs against as it travels. If they are white or a light tan, they are new (as most likely the chain would be). If they are beer-bottle brown, they are shot. Even if the chain looks ok, you're going to have to do the job.

Oh yeah - here is the funny part - they are under $10 a pop (plus the pins that hold them in place)...

__________________
Henry Bofinger
1989 560 SEL (black/black)
2001 Audi TT Roadster (silver/grey)