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Exhaust Finned Nut Spanners

December 21, 2015


I now have Exhaust Nut Spanners, for Airheads, in stock and ready to ship.

These are an important maintenance tool for any Airhead owner. The finned nuts, where the exhuast fits to the cylinder head, need to be loosened, cleaned, lubricated and re-tightened regularly - to reduce the chance of them seizing and damaging the thread on the cylinder head, which can be expensive to repair. Opinion varies as to how often this should bew done - some say anually some, like me, do it when doing a full service.

 There are several good articles on the internet and elsewhere about this topic, and I advise you to read them also to find the method you are most comfortable with before undertaking this job for the first time. It isn't difficult - but requires some care. The following is my method;

 Care must be taken when undoing the finned nuts - if they begin to loosen and then get tighter again I strongly advise that you stop and cut the nut off. New nuts are readily available and far cheaper than having to have someone repair the thread for you.

 I like to remove the nuts with the motor warm. Providing the nut unwinds and doesn't get tighter (usually around 1/8th of a turn), I spin it right off the head and let the motor cool before cleaning the threads, of the head and nut, and the split sealing rings with brake clean and a soft bristled (copper) wire brush and rag. Making sure to remove all the old anti-seize compound and any carbon deposits etc. It is important to make sure there are no traces of any oil or WD40/ CRC left on the parts as these will promote a build up of unwanted hard stuff once reassembled. It can sometimes be necessary to chase the thread with an appropriate thread file to clean any burring up. I then refit the nuts with a good smear of high temp anti seize compound on the threads. I retighten the nuts with a medium size 1/2" drive strong arm bar to "reasonably tight" but not as tight as BMW recommend - DON'T OVER TIGHTEN THEM!

Now if the above isn't the case and the nuts are realy tight I give the handle of my strong arm a tap with a dead blow hammer, taking it very quietly and watching how far the nut moves - it should loosen within the first 1/8th turn and continue to do so. Penetrating spray (Nutcracker/CRC/WD40) can be used but if it feels dodgey I stop and cut it off.

 To cut the nut off I prefer to use a hacksaw blade, but you can slo drill a line of small holes that don't penetrate the thread. Cutting down to within 1mm from the thread on the head - be very careful not to go too far and damage the thread. Then I split the nut the rest of the way  with a cold chisel in the cut, again being careful to avoid damaging the thread by going too far. Once split you can carefully unwind the nut and replace it. Then clean everything up, lube and tighten.


Thanks for reading,





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