hi guys. i need help, the bike is really hard to start when cold. i mean reaaaaaaaaaally hard. but then, when it's hot and gets to reserve it does the same thing, takes ages to start again. anyone suspect what could be causing this? thanks in advance. cheers.

Could be a dirty fuel tank or the fuel filter on top of the fuel tap.
Change the inline filter and the one where the fuel hose joins the carbs (on a 3tj).
Dodgy spark plugs would be next ... even if they look ok and spark when you hold them on head they still might need replacing.
Check the EXUP valve is opening properly.

Valve clearances .... though, that would be my guess

valve clearence? that doesn't sound good. what can i do about that?

Check them I suppose ... but do the other stuff first