Carb Problem - Bogging down half throttle :(

Hey guys! I have a 50CC scooter which I bought all messed up with no engine working etc. I had a friend restore it for me if I bought the parts, and he suggested I buy a 70CC engine. So I did... as far as I know all the parts are for 70cc too (mechanical not sure about electrical).

My problem is, about half throttle the engine starts to bog down and then it will cut out if I don't throttle to full. It's fine at idle at lights etc. It's also fine at full power. It's just when Im going slowly through a town or something It's embarrassing when it cuts out & have to start again :banghead:

But I cleaned it the other day, Yahoo Answers suggested it. I was relieved that it worked ! But then 2 days later it started again cratch: Really not sure what is happening...

Is it the air filter? or maybe the mixture is wrong in the carb? (unlikely everything left stock)

Or could it be to do with the jets because when I took it apart I just done them up tight, someone told me I am supposed to turn them a certain amount??

But then I looked for a manual for my carb and I couldn't find one! I have a Keihin PWS. I really don't want to buy a new carb for this they're £100+ :cry:

Please help anyone! Thanks!!!


**EDIT** ATM The bike has no Choke!! I have bought a new one but it hasn't come! Maybe this is the cause? It is connected but unplugged because the connection snapped of the end. But even before it was snapped It was doing this.. Can't be sure that the choke was working then though because when I first had it I had to leave the bike to warm up and it would work fine. Now I Could leave it warm up for an hour and nothing will change