idle?

Jumped started the bike as the battery is knackered, and it fired up right away, after being stood for roughly 4 months due to crash, one of the radiators starts leaking so I need a new rad, But it wouldn't idle, if its not started it reads -1, once its started it reads either 0 or 1, and I...

On the way to work today , in the pishing down rain, my idle speed suddenly increased to 2k'ish and stayed that way for about 5 minutes of filtering / stop / start riding ... then it dropped to the usual 750 ish rpm Any uideas or just electrics and rain bad combo ? :dunno