If its too high on the H, and you have limiters on the carb, get a 2mm allen key, put it in the H thru the limiters hole, engage the H needle, and give yourself a few extra clicks anti clockwise to drop your rpm to 13500 or what your wanting.
make sure the key is seated well in the H needle before you turn it, there are small nylon teeth on the limiter that engage with the steel needle, using allen key will move it past them.
Providing you have gone thru the carb, put a kit thru it, and made sure you dont have a blocked fuel filter or air leak etc, and all other usual disclaimers apply.
edited to add.
As already mentioned, clean your clutch drum, if its ok, and the bearing is clean and has grease, your clutch springs might be a bit weak, cluch engagement should be around the 3600 rpm, so chain creep may be from a dirty clutch drum, or bearing, or weak clutch springs, the springs are only a few dollars each, so easy cheap fix.
also, if the idle is a bit high, use the L to richen it up to 2500 rpm, if it loads up when idling for 30-40 seconds, then lean it a bit back up to current rpm, and then use the LA to drop your idle to 2500.
