So I've been riding to work that last few weeks with no problem starting (since i got a new battery anyway) regardless of the cold (1 deg C).
I was away for the weekend so it's sat for 2 days with no attention. when out this morning to start and the would crank but not start. the first time it chucgged but nothing. i tried starting with the petcock on prime - nothing.
btw. i normally start her with about 1/8 throttle.

gave the throttle a few big twists and then tried starting as per normal (1/8th throttle). she started up with a big rev before catching the choke and nary a worry after that.

to me it seemed that there was no petrol in the cyclinders and needed those big twists to get some in there. is this reasonable or is this just the hint of a larger issue?

Twisting the throttle with the engine off will do exactly zero.

How long did you have it on prime before trying to start it again?
How much Choke are you using when you do a cold start?

cold start gets full throttle and an 1/8th of throttle normally. if i do it with no throttle then occasionally it won't seem to 'catch' the choke and will stall.
i turned on prime for prob about 20-30 seconds. then tried starting while still on prime with nadda result. turned back to on and gave the twists and she started after that. maybe the twisting was just giving it extra time?


the 'normal' process for me is full choke, 1/8th throttle, starts first go. picks up from about 2k RM up to 3k. let it idle there for able 30sec while i do up my jacket. slide off some throttle (the RPM will actually rise to about 4k before reducing back down) till its at about 2k.
Put on helmet and gloves, by which time the RPMs have increased back to 3ish. slide off the choke till its idling at about 2 again, reverse the bike out, reduce choke till abut 2k if its changed. ride around the corner (about 800m at a sedate pace), turn off the choke completely and ride to work.

temps of a morning are around the 1-2 degree Celsius mark if that makes any difference, so the bike is definitely getting a cold start of a morning.

You shouldn`t need throttle on choke,perhaps it`s time to check the colour of your s/plugs.I`d check carb diaphragms for tears,inlet rubbers for leaks,mixture screws and float height.Be as well to clean Jets/carbs while at it.Also Fuel and vacuum lines for splits.