I finally got the engine running the other day. It ran fine but one of the small valve covers was leaking. I fixed that then tried it a few days later. It seems to only run with the choke on. If I shut it off at all it stops immediatley.
The engine is a 18HP B&S twin cylinder.
he engine is almost new but had some nternal problems. What shoud I check first?

I took off the top of the carb, there was plenty of fuel and it looked clean (needle valve not sticking).

kaw550
It sounds like the carb is running lean. It may need an adjustment on the high speed screw but without the model and type number I can't look at the parts drawings to see what type of carb you have. Maybe give me the model, type and serial number so I can check further.

snoman

yeah my mower was running too rich adjusting the screws while its going should fix it