How do I clean a gunged - up radiator?

The radiator on my Kawasaki ER-6f is so clogged up with crud that I am concerned it isn’t going to be up to the job when the weather warms up again. Is there a product that works on the aluminium, or any tips you’ve got for sprucing it up without wrecking the core as it looks delicate.

Alex Cotterill, Oxford? Answered by Chris Dabbs, MCN

You need to be careful because rads are delicate creatures. Caustic soda or even a weak acid solution will eat into the alloy. Even vigorous brush work with a detergent could flatten the fins. Try soaking the baked-on dirt with a sponge to soften it before using a garden hose set to ‘spray’ or ‘mist’ to rinse it out. If the dirt is totally dry a high-pressure airline can be effective.