I think my mower has the wrong muffler fitted to it.  The one on there is this one   
https://www.outdoorking-forum.com.au/index.p...ath=193_195_375_526&products_id=2268 But from according to the parts list I downloaded when my subscription was valid I should have this one which seems a lot bigger   
https://www.outdoorking-forum.com.au/index.p...ath=193_195_375_526&products_id=2262 Not sure of the differences between these two mufflers other than the physical size, just wondering if the smaller one is providing too much resistance that could be causing a problem??
Nathan