valves adjustment

hi all my silverwings got 64000 on the clock now on a 2004 i had no service history when i brought her.just wondering if there are any tell tell signs of them being out of adjustment.the scoot is running really well at the momment just replaced all fluids and air filter which was black as hell .thanks for any info

thanks for the info bigbird just dont want the scoot to become unreliable.im planning on fitting a j costa if i can get one here in the uk do you or others think this would be a wise move with the milage on the bike cheers all

cheers bigbird coming home today on her i noticed a slight judder low down as if the fuel injection doesnt know what to do.i have just changed the spark plugs and the air filter which is a standard one.i was wondering where the fuel filter is and how easy is it to get to.as i dont know when this was last changed .also can you balance the throttle bodies or do these never need doing.cheers for any help