Another thread on cold rears. Mine when fired up on choke ( NC30), the No.1 downpipe remains cold. I've checked the plug by switching it with the No.3 but still the same. I've checked the HT lead and coil and all appears ok. The float heights are all ok and the carbs have just been synched. As soon as I can apply some throttle the pipe begins to heat up but remains stone cold when on choke. When fully warmed, the bike runs like a dream. Any ideas?

does no1 plug fire OK in no3?

I'd be thinking plugs usually if it has just started..

Plugs are perfect, both firing ok in No.3, there brand new. It definitely doesn't seem electrical given meter readings I'm getting.

Valve clearances?

Would valve clearances have an input? They haven't been done in about 5000 Miles but sound ok.