Derbi senda baja 125cc cams and timing help

[Cupidstu]

Hi every
This is my first 4stroke bike ever had many motox bikes tho

So the other day I tryed to advance the timing a little but chain come off

Long story short I need to reset my cams cam chain and timing ect

I have tdc and can time the bottom easy but where should my cam sit lobes facing down? Then line the cam sprocket then timing ect any help would be amazing as this is stressing me out so much.


I tryed this way and the bike doesn't start I had smoke like stuff coming out my air box lol :/

[Cupidstu]

Update
I now have it timed up ect and starts but it's a pain to start from cold
And when I start rev fast it cuts out and when I do it's slow to full throttle it's pops and bangs as I let off the throttle could I be a tooth out?