I've just spotted this thread and realised that I too had a couple of problems on Ruta 14 back in December 2009. I can't tell you the KM marker but it was between Gualeguaychu and San Jose, so relatively close to Buenos Aires.

I was stopped twice; the first time I was asked for papers, the second I was told that I was doing 130km and had been recorded on a radar. I managed to successfully deal with both incidents trouble free.

I had all my paperwork in order but for the first time in South America the police requested for "seguro" - insurance. I carry a fake laminated international insurance card with details of my bike frame #, registration etc, and then handed a paper supliment to my driving license, which the policeman assumed was the counterpart to my insurance. I was waved on my way.

My advice: carry some kind of fake international insurance card/papers. I have carried mine for 48,000 miles and this is the first time I've had to use them.

The second stop was on a stretch of road that had numerous signs warning of police radars and I was therefore very mindful of my speed. It wasn't long before I was waved down at a police check point. My tactics at police check points are always the same:

Overshoot the police checkpoint. This isolates the policeman from his colleagues and helps any negociation to remain private and allows the policeman the opportunity to wave you on your way without losing face

By over shooting I had time to remove my crash helmet and ingage in a quick and friendly conversation with a truck driver. By the time the policeman arrived I was all smiles and ready to greet him.

I assumed that all the policeman wanted to ask was the normal "how fast, how much" question, so immediately I greeted him with a friendly "como estas". He quickly told me I had been caught in a radar at 130km which I knew was a lie because I had carefully stuck to 100km - I pointed to my GPS and said it was impossible because my GPS recorded my speed... I was still very friendly and with a grin like the cheshire cat. He asked me where I was heading and I used the opportunity to explain I had been to Buenos Aires, that I love his country and that everyone here is "muy sociable"... his chest puffed out a bit.

I should add that my Spanish isn't great and that during the conversation the policeman tried the 130km line on me a couple of times, but I just waved it away with a smile and an "impossible" pointing at my GPS.

Anyway, I was soon waved on my way with a big smile and a handshake from the policeman.

I hope that helps someone