A temporary/intermittent interruption in power is more than likely going to be an HT fault. It is not unheard of on XTs (and a lot of other bikes) for the joint between HT lead and coil to let in a little moisture in extreme wet weather. The best way to solve future problems is to coat the outside of the joint with silicone grease (when everything is dry). It will be more effective than WD40 in the long term as it provides a thicker seal against moisture penetration. WD40 is good for displacing moisture initially, but once it has been applied it doesn't have a long-lasting effect.

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