One of the most difficult parts of a motorcycle to keep in respectable condition are the exhaust down pipes. They go through extreme punishment. Heated and cooled, have all manner of debris thrown at them and are difficult to get to. I had heard about toilet cleaner being the answer but was very dubious about it. Especially on a nine year old machine.
However I came across a YouTube video which convinced me to give it a go.
I applied the Harpic and left it for five minutes. Most of the stains and rubbish came off. I washed it off well but some stains remained. I gave it a second application and this time after drying I used chrome cleaner. The photos speak for themselves.