Small Engines (Lawn Mowers, etc.): carb problem, troybuilt, breather tube

Question
I have a '79 Troybuilt Horse w/Briggs 8hp(195432-?-79033012). When I got it it ran ok (occassional backfiring) but otherwise ok. It has been sitting for a few years, but now decided to get it going again with a new breather tube, air cleaner, and thought I'd rebuild the carb while I was at it. After the rebuild, gas leaked out around the lower air inlet tube,choke,etc. I figured that I disturbed the float setting and it was overflowing ..but it ran pretty good! I took the carb apart again and bent the tab on the float up a little to close the valve sooner. No more leak but barely runs, kinda sputters not firing on every stroke. I tried again but no improvement. Also, the rebuild kit had parts for mine as well as newer than 820327xx engines. Most of the parts were obviouse: 2 different gaskets, 2 different fuel valves, etc, but there was a small rubber "washer" for lack of better word, about 1/8" dia, and 1/32" thick with a very small pinhole in the middle. I didn't see anything like that in mine. Suppose I missed something?  

Answer
 Hello Scott:

 The Small O-ring you are talking about is the Seat for the Float Needle. Look inside the Carb Bowl Where the Float Needle enters the Carb. At the Bottom of the Hole is where this seat Goes. If the Float Needle has A Rubber Tip (Looks Black) then DONT USE the Seat. If the Needle is All Steel, USE the Seat(Needle is Shiny from end to end). Turn the Carb Up side Down so the Float is on Top. Set the Float so that it is Parallel to the Bowl Seat. Hope this Helps.

 Good Luck

 Respectfully

 John