ok ive fitted ethos half system but ive not changed jets yet , running 115/118 i know i should be something like 118/120 , my question is will the bike be running lean as it is , ie melted pistons etc, forgive me but im not so clued up on the jetting side of things, should i not be riding the bike until ive changed the jets

ride it and see how it goes. It may perform lovely for you - or it may seem to like the revs but not actually go..so you can feel it is lean.

you'll not be melting pistons mate....I hope!

You would have run a lot smaller jet size than that before you melt pistons,
You will need to change your jet sizes to complement your ex system for best performance.
Iran a full race micron on my bike for a long time without changing jets.

to be fair i had 126 front and 124 rears on my ethos with maggot can ran very nice, a tad rich but i like to run slightly rich its just my prefrence, never hessitated on pick up or spluttered just depends how it suits your bike

take my race bike now tho i cant even start the thing grrrr !