I have an older OS 40SR engine and am looking for the bolts that attach the muffler. The housing of the engine is tapped to accept the bolts rather than having the bolt go through with a nut on the back. I no do not have the original bolts so I have no sample to take to the store. It is about a size 6 but a 6/32 is not correct. I wonder if it is a 6/40 but I cannot find that size. And metric sizes do not seem to fit.

Thanking in advance,

Laurence