Small Engines (Lawn Mowers, etc.): Onan Carburetor troubles, vacuum leak, diaphgram

Question
I have a Onan 18 Hp aseries 48 engine that I rebuilt the card on about a month ago.  Used Onan genuine 142-0570 parts kit and it worked great for a couple of days. It started quitting after running for awhile and I suspected that it was vapor locking because it wouldn't pull gas nto the filter.  I could get it running again by priming the carb (pouring gas down the throat).  Now it won't run at all unless you pour gas in the carb.  I suspected that the diaphgram might have streached and lost ability to pull fuel but it will pull it up into the filter.  I saw that their has been a problem with the float in these carbs and now I'm thinking that nmight be the problem.  I have takern the carb apart several times and there is nothing that is stopped up or anything.  The only nway to get the diaphgram is to buy a kit and they are expensive.  I have seen a brass float that is available for around $25.00.  What avenue do you think I should go down next?  Float or diaphragm?, or could there be something else I'm missing.  I know the float that's in there now is hard to get out sometimes so it may be sticking.  THANKS for your time.

Answer
Lets rule out a vacuum leak or fuel pump problem.  Take a small fuel tank and hook a hose directly from the fuel tank to the carb.  Make sure the tank is higher then the carb so the fuel is gravity fed.  IF this resolves your problem you have a vacuum leak or a fuel pump issue i suspect.

I apologize for the delay in getting back to you, I have some engineers here from China I have been working with.