onan carb questions (float)

Well I have a new (to me) GT-18 Hydro 917.257070. It has led a rough life and I'm doing some of the "routine" maintenance that has been ignored for some time.

I disassembled and soaked and cleaned the carb. I reassembled with the old gaskets and float and it ran great, for a while. It now runs like poop.

The next to do items are new fuel line from the filter to the tank, and a float for the carb (it has the "original" foam type float).

I have searched and it is recommended to buy the brass float.

My question is: should I buy the Onan brand float with the assist spring or can I buy the knock-off and get the same results?

The Onan float is about $50 and includes an "assist" spring. http://onanparts.com/index.php?main_page=product_info&cPath=1_12&products_id=287

The "off brand" float is on eBay. It runs about $25. http://www.ebay.com/itm/ONAN-146-0380-CARBURETOR-FLOAT-BF-BG-B-43-B-48-/120821948682?pt=LH_DefaultDomain_0&hash=item1c218ca10a It appears to be compatible, but does NOT have the float spring.

Do I NEED to spend the extra $25 for the spring? Has any one bought the knock-off and then had to replace it with the onan to get it to run right?

I'm torn...

Thanks for your responses.