Let me tell you what I did to my 3250 ST. I got it at a swap meet, did not have a carb and no sleeve in the engine block where the carb goes in. I bought an ASP .91 carb, which was recommended as a good carb for this engine, and it was too small where it goes into the block. I found a piece of aluminum tubing and it fit real tight around the carb base, but it still lacked a little to fit tight in the block. I wrapped a couple of turns of aluminum tape around it, and then cut some aluminum strips from an aluminum pan and wrapped it, lettint it overlap at one point. It then inserted fairly tight, and I put some muffler glue around the top. I tightened the bolt that goes through the carb. If I try to put sealant around the carb flange that I made before I insert it, it just pushes the sealant (glue) out. Do you think this set up will cause any problems, or do you have a better suggestion?