Re: robin ht200 carb question
I have had this problem many times. Especially with the old engines. I suggest to look at the gaskets/ diaphragm and look at the diagrams on ebay. Usually all you need is a new or cleaned inlet filter and a diaphragm. Just because the listing for your unit asks for a number, I always use the numbers on the carburetor. Manufactures change parts a lot.
Also the Walbro site has a lot of instructions etc.
Remember some kits are universal for many carburetors.