Thanks Norm, maxw and AVB
This mower has not been fiddled with before I picked it off the street years ago and when I pulled it apart the other day the three cowl bolts were tight. When I mucked around with changing tank/carbs around I can assure you the bolts were snugged up right afterwards. The manifold tube bolts at the cylinder end were tight and the gasket was perfect.
Had a good look today and yes, there's only a very small gap between the edge of the cowl and the tube, the O-ring and white plastic grommet where the tube mounts into the carb are sound. Can't imagine how there would be enough vibration to let the cowl edge grind down into the tube from motor overrevving, or some harmonics thing.
I'm thinking it might be that the painfully thin metal that the cowl is made of might be allowing some flexing when the starter cord is pulled, not something I can observe whilst tugging on the cord :-)
Anyhows, if the duct tape repair fails the lower cowl edge will get a bit of a grinding with my trusty Dremel .
BTW I do a lot of mechanical mower repairs/maintenance for myself and friends, family, etc. but not for $$$$$. In return people give me stuff they or others don't want, can't start, have chucked out, whatever. I currently have 25 + working mowers which get abused keeping our rural property sort of nice and don't cry too much if and when they break or expire.
Lately though brushcutters have been arriving as gifts or to fix and at Xmas lunch yesterday our host asked me to see what I can do with a Tanaka and a Shindaiwa which he hasn't been able to get started for ages. Neither had air filters and no evidence of ever having any maintenance. They are obviously high quality machines, both are now running and I have sent a note to ODK Online store with a beg for parts needed.
Thinking maybe in future I might do some brushcutter repairs for a bit of beer money, perhaps just specialise in Hondas of which I now own three, and a couple of Honda clones. The Shindaiwa B450 is an absolute beast, pity it's a 2 stroke though.........
