Ive not heard of any problem like this on the forum, but take Kevs advice and ask the mechanic to look at the things he listed. Hes a proper mechanic and knows what hes talking about as he more than once had his bike in pieces playing about with it, adding this that and the other, all just out of the usual biker spirit of you have to tinker.

At the moment ive had the bike fail on me 2 times, once when one of the electrical connection blocks on the left side under the tank rusted through causing the bike to die, and the next the same area the main head light cable split at the connector (lucky i was at home and not night riding.)

Not too be harsh on yamaha it is a good bike, just some of the workmanship in certain areas is lacking ie the electrics in the routing/connections, and the quality of the finsih.

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Plough on