Shifting corroded nuts and bolts

Q. I want to replace the standard exhaust system on my 34,000-mile Kawasaki ZX-9R with an aftermarket system, but all the fixing nuts and bolts are corroded solid.

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I managed to get the larger collector box nuts off with WD40 and a long extension on the socket, but I’m wary of tackling the 6mm thread nuts that clamp the downpipes in place in the same way since I snapped the stud off one on my last bikes.
Thomas Kitchener, email
 
A. If gentle application of pressure after copious use of penetrating oil hasn’t worked, then your next step is to apply some heat to the local area.

Get a propane or butane canister from a hardware shop and fit the biggest nozzle you can find ­- 30mm is a good size. Don’t use an acetylene torch with a welding nozzle because you’re likely to overheat the area.

What you’re trying to do is warm the nut, but not the cylinder head or the exhaust pipe.

Give it a blast, then try and loosen it, another blast, another twist. If the nut glows red hot it’s too hot.