1) yes.... 4g15 n 4g13 using the same carb....
2) jeng jeng jeng...
3) screw in means clockwise... similar to water pipe... wanna close the tap (lean mixture), u turn clockwise....
4) the workshop usually tune my carb and ignition timing only charge me 5bucks... other workshop i dunno... but shouldnt be expensive....
hmmm this photo very familiar :X-: