Well done so far.

Now you have a leanness in the idle circuit. Normal is roughly 1.75 turns out. Try adjusting the mixture screw a little in either direction to see if the prob goes away.

which screw should b approx 1.75 turns out (screw where airbox meets carb or tick over screw) ??

Air Screw should be adjusted.

My mate sorted the problem on saturday, after we managed to get the bike revving niceley, as said previous, it still kept bogging at low revs, tried adjusting mixture screw with no joy. My made opened the carb back up and lifted the needle (clip i think) to the middle. Bike seems to be running great!!!! So i had a few hours playing around on the mountains. Thanks for your help boys!!!!

Hi just wondering if anyone can help I have a beta 125 2004 trials I went out today and revs stuck on full and I pulled kill switch no joy still didn’t cut out so had to put ht cap off checked carb and throttle in fine not stuck not nicks in cable slider hits bottom carb fine soon as I start it just revs up full any ideas thanks 

Could be air leak in manifold between carb and cylinder. Pretty much only thing I can think of if slide is retuning properly to rest position in carb. If the bike revs up again stick something over the exhaust to drop the revs then the kill switch should work. When an engine is screaming the ignition of the mixture can become self sustaining. The other thing that can happen is there is so much primary ignition current being generated the few ohms resistance in the kill switch can leave enough current in the primary to keep firing the plug. I’ve pulled the plug wire too. I’ll never do it again. Pretty sure I felt my heart stop. 😳 Didn’t like it. You might want to check the ground connection of your kill switch. Beta did a stupid wiring setup on some of the rev3s where they grounded to a lug behind the number plate to the triple clamp. Caused dodgy kill switch and lighting behavior. I always ran a larger ground wire back through the harness to a hard ground point on the frame. Specifically one of  the mounting screws of the coil.