Help me before I go to a shop :(

Brought my first rs125 last week.. It's an X reg that's been sitting unused and not been started for 4 odd years. Paid £400 for her!
changed all the fluids, spark plug, air filter sponge, fuel/oil lines, cleaned the carb and a new battery. Now she starts but only with the choke half on and my hand over the air box intake and if you take the choke off it'll cut out and you can't rev it at all.
I done a compression test and it read 110psi.
Checked the reeds, inlet manifold etc for splits or air leaks
Anyone got any ideas of what it's likely to be? Before I end up replacing crank seals, piston rings and all gaskets... Don't want to be wasting my money to find that's not the problem
Any help would be appreciated!

 

personally id just go all out and do a proper rebuild checking everything and cleaning everything/replacing consumables. the rs125 has a "temperamental" engine as my brother calls it. it has to be running right and it has to be looked after properly. but with it wanting to be on choke and hand over the air box intake id still be looking at it getting too much air, does it have the right jet? is the mixture set right? im sure somebody a little more knowledgable such as stevep will be along soon.

 

stick a bigger main jet in there, and make sure that your mixture screw is set right, sounds like its running too lean, also check your exhaust isnt blocked, if its been run on cheap oil it will need a rebuild and maybe a new pipe, they are high spec motors and need looking after well. also try changing your plug again.