Vintage Dirt Bike Q & A

Hi folks this is my first time on and am glad this forum is here. I bought my son an old 1984 CR80 project bike. It is missing the sub-chamber for the exhaust. Can anybody tell me if this a must have part on the bike. The previous owner removed the chamber and filled the butterfly area up with RTV or some rubber-based goo. Are they even available anywhere? Also plastic parts are all boogered up and I am looking for suppliers. Any help would be greatly appreciated.