Ducati John

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Corrosion to horizontal cylinder plugs and coils

Even a pristine bike can have hidden issues!!

749/999 models and S4/S4R Monsters that have the "Plug Cap" type integral coil fitted. I have had problems with a number of these caused by a not so good seal.

The photos shows a coil and plug from a pristine 999R that developed a misfire. The corrosion caused a bad connection between the coil and the plug. A new plug and a clean up of the coil cured the fault. Another was an S4 that whilst clean had obviously seen a bit of weather. The problem here wasn't a running fault as it was fine when it turned up for a service. The problem was that the coil wouldn't come out of its hole! The outer steel core of the coil has corroded and swollen jamming it in place. Skillful use of a 3/4" drill bit got it out, however not in one piece. To prevent this I recommend pulling out the horizontal coil after wet runs whilst the engine is still hot. This should allow any water to evaporate off. Dry the coil too and give it a dash of WD40 as it goes back in. Now if there is a lot of rust evident, don't as I once did remove the plug without vacuuming or blowing any rust particles out of the plug hole first. The first bike I encountered this problem on was a 999, the loose dirt went in the plug hole and dropped into the squish area stopping the engine from turning over properly. Honest truth. Head off job!!

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