I picked up a 17b a few weeks that had sat on a shelf awaiting a rainy day. Today was that day. The first hurdle I hit was the pump leather. I can’t figure out how to unmount it. I was expecting something like a C-clip, but have no idea what to do with this: Are those two slots at roughly 11 and 5 o’clock that I’m supposed to fit something into to unscrew it? If so, what’s that something called? The second hurdle is more troubling. A quick dunk test showed no problems but when lit the stove doesn’t hold pressure and weeps fuel from the neck. I thought it was the odd-ball fibre washer, but after replacing that with a lead washer the problem persisted. I think these are the culprit: …or am I mistaken? Given that there are two might they be marks from manufacturing? I will try another dunk test tomorrow and see if any bubbles originate from these marks. -R
A bit of diluted washing up liquid dabbed about the area might make pinpointing the leak more accurate than immersing- or easier to see, at least!
@IRM Sometimes the threaded stem that the small pump washer assembly retaining nut is screwed onto is intentionally burred over, when I’ve removed/replaced a washer by unscrewing the pump knob and sliding the washer off/on from that end. You’ll still need to unscrew the larger nut clamping the pump washer in the assembly, but that shouldn’t be too difficult if you get a grip with pliers on the slotted nut. Regarding the pressure leakage, maybe the lead washer needs to be crushed a bit more by screwing the vapouriser in tighter? But yes, one or both of those marks could be the culprit(s) I suppose, in which case a skim of solder would seal up the leak.
Thanks @presscall - clamping the flats behind the leather in my vice and unscrewing the ring at the front with my pliers did the trick. @Blackdog a dunk in much hotter water showed a very small leak between the neck and the vapouriser. I have tightened it as much as I dare. Perhaps I need a thicker washer. -R
Good plan, don't be tempted to stack another lead washer on top of the old one, I'm sure a lot of us have come across that in the past! Paraffin stoves can normally be pressurised by the pump before a dunk/soapy water test, that way you can get right up to operating pressure and not miss a leak. Cold stove and hot water is the only easy way for self-pressurising stoves but you can't achieve much pressure so it's a poor second and doesn't always show up problems.
I did both - pumped the empty tank and let Charles’ Law lend a helping hand. It turns out the problem is the vaporiser. It has something of an edge rather than a flat rim at the tank edge (RHS below): Comparing it to another one shows an obvious difference in size and it doesn’t seem to screw quite as far into its socket on the tank (LHS below): Suggestions welcome :-) -R
I will have a go at a thicker lead gasket. I am wondering if the best way to make that is to (try to) cut one from a small sheet of lead I have using the same set of punches I use for viton, or to have a go at casting a gasket. (I have about 10-12kg of lead on my old diving weight belt) -R
Cut one from sheet- punches should be fine, or drill the centre hole and cut the outer diameter with scissors...
2019 production Prabhat No 1 needed lead fully 5mm thick (?!?) to keep riser from bottoming out in tank boss so hammered flat, snipped, plinked round & drilled a 1/2 ounce bank sinker fishing weight. Calling that one the Prabhlem Child. Or Prabhably Not.
