How did you figure out that our needed the diaphragm and gasket replaced?
Well to be honest - I didn't "figure it out".
I've done a bit of work on the 2 stroke, but very little on the Briggs 4 strokes - so I have been reading/studying up on them lately. One of the articles I read (by a bloke who seemed to know what he was talking about) had a quote that stuck in my mind.
90% of the Briggs and Stratton engines that have starting problems can be solved by cleaning the carburetor, fuel tank and replacing the diaphragm and gasket.
So I didn't really figure it out, I just assumed it was a safe bet - it was only $10, and if I was wrong, at least I learned how to do a very common job.
I bought them down the local shop for $10 (only because I wanted them straight away), but Bruce has them for $11.00 for the original Briggs or $5 for aftermarket - so if you have time to wait - the $5.00 version from Bruce (Outdoorking shop) would be the best best.
So I just took a punt - for $10 - to see if it worked - worked like a charm. Even if it didn't work - the $10 was well spent because I learned how to do that particular job. Good result
