Need to know what you are working on. Engine/drive package. If you have the metal one, simply use some spray carb cleaner. If it's the K&N type (Gauze or paper) follow the manufacturers suggestions.
If you think the flame arrester is causing your problem, remove it and see if the engine starts normally. Run your bilge blowers at least 5 min and ensure that you do not smell fuel and have a fire extinguisher handy.
btw, flame arresters RARELY cause starting problems......
I go with either dish soap and hot water and blow dry with compressed air or varsoll soap, hot water and compressed air.
it has to be some plugged for the engine not to run, check carb for lots of crud.
rob
