i also had the same problem. i fixed it liao
there is a cable from the top to the left side of ur front wheel. speedo wire. ur friends are correct, its the wiring,
i changed mine like abt 60 dollars and its workin fine, did it at wing yap amk. ppl tell me expensive but since its near my house then bo pian.
most likely is the same issue as mine. just tryin to help. if wrong dun blame me,,,