A temporary solution that helps a little is to "tack" up the hill. It is somewhat like a sailboat zig zagging upstream. It turns a big hill in to several little ones. It takes a little practice and you have to be on a street or road where it is safe.
Make sure your spark plug is clean and properly gapped. Make sure your belt or drive chain is adjusted properly and make sure your tires are properly inflated. Also try a higher octane gas in your gas/oil mixture.
Check the spark plug first!
All these are little things you can do and may help.
The best hill climbing mopeds/nopeds I have are the Vespa Gande,the Puch Korado and my persoanl bike a Honda Urban Express. I weigh 220 and the Honda Urban will take me up about a 23 degree hill from a dead stop at the bottom. They are all 50 cc engines.
Good luck and Happy Trails (may all your hills be small ones)