I have a 3.5HP Briggs and Stratton "sprint" type engine. Model 407902 Type 072 01 Code 96081464 The numbers were hard to read so apologies if a digit may be wrong. Anyway, the mower would not run but instead backfires on ocassion through the carburetor. I have removed and checked the blower housing timing pin (can't remember what it is called) and it seems ok. I have set the valve gaps as well. There has been no change to the backfire problem. I don't have a compression gauge and just do the finger over spark plug hole trick. There is weak compression. My question is - Is it possible for a low compression problem to cause backfires like this i.e. through the carburetor? Thanks for your help.
Hi sparker, I get a few like that but I just throw them out, not worth wasting my time on them, but I have always assumed that the problem is with the inlet valve not seating properly which also contributes to the low compression
Thanks Norm. This one is going into the spares bucket. Wasted far too much time on it. You're probably right about the valve. I did have a look and it seemed OK so I give up.
