im having simular problem on my mfi unit on my s2 ive changed all spark plugs and ht leads dissy cap etc mine now starts but once it gets to normal running temp and i turn it off it starts up again but idles at 250 300 rpm and is really lumpy and doesnt wanna pick up speed people have told me it could be the esc (electronic Spark Control) dunno if a S1 has this hope this can help mate i no how frustrating it is and also having someone on ya back 24-7 lol good luck