You can add a few holes to the aluminum 'balls' structure. If you double what's there in San opposed fashion, essentially drill holes opposite of the existing ones at each chamber.
It's really a fantastic design, using chambered resonators to damp the different frequency.
The biggest thing is keeping it clean, yours either has super low miles or was cleaned up, that helps a lot. Modern 2t oil will keep it from gunking up, but most times you get them and they are plugged.
The 14 will probably help some but you will want to get the right parts to set it up, look at Myron's mopeds for the correct atomizer, needle, slide and jet.