I have put in a new fuel pump diaphragm and have seemed the carburettor. She idles okay but as soon as I put it in gear the engine dies. Any suggestions? I bought this engine secondhand so I am hoping is not a lemon. The engine has been standing for three years. Could it be a perished fuel pipe?
If it has sat up for 3 years, then most likely the carb us gummed up. It needs to be taken apart, thoroughly cleaned, blown out with compressed air, and reassembled with new gaskets, needle and seat.
As with any engine, confirm Compression and Spark on all cyls and that no water is entering the exhaust. It may seem to be working properly while running on 1 cyl but you will not notice a prob until you rev it up.