Both my 96's are running fine, pump and hold pressure just fine and are not leaking. All is well, I think... 1. Is it normal for the pump rod to be pushed back slightly at the end of the stroke? Both of mine do this, even if the filler cap is removed and no pressure is building up in the fuel tank. 2. I would like to use these on backpacking trips. Should I use a rubber washer under the reserve cap or does it make a reliable seal against the lead washer?
I have two '96's and yes the pump rod pushes out a bit. Don't know why that happens but it doesn't seem to cause any problems I leave it naturally extended when it's running and just push it back in gently when I dismantle for packing
The lead washer should do the trick (I carried a late '30s N°96 on my bike for 6 days this august without a problem) but I've read here about people using an extra thin rubber seal just for sure. I did make sure the stove sat 'upright' in the bag to avoid any problems. All the best for 2015, Wim
The seal in the blanking plug on the tank, for transport, is usually reliable. Unless it's really worn & perished, or unless you're obsessive about doing a thorough job, leave it as it is unless it is actually leaking. You see, for transport the stove/tank shouldn't be under pressure, so apart from gravity there's no internal pressure to make it leak. The tank plug has internal threads so it can double as the thumb push on the end of the pump rod. However, the lead seal in the female thread on the tank top is another problem altogether. This forms a seal between the vapourising tube (colloquially known as the 'lipstick') and the tank itself. It needs to seal when the stove is running, so needs to be heat resistant, and to resist the internal pressure Historically lead was used to do this, but it is a hit & miss affair. If you're lucky it will work OK, but it is the weak point of these stoves and often leaks or seeps in use, thanks to internal pressure. The lipstick is tightened down and squashes the lead to form a seal. Unfortunately after time and repeated tightenings you run out of 'squash' and the joint starts to leak. But these stoves are very old designs, I'm sure there must now be some heat resistant hard rubber that could replace the lead. I would be interested to hear about his; perhaps some of our more knowledgeable members could tell us more? In the meantime I have sorted any seepage by making a homemade synthetic gasket that was left over from a carburetor repair and placing it over the lead seal, which was left in place. This sort of combination produces a thicker gasket overall and is usually enough to cure any leaks No bad thing to include a roll of PTFE plumber's tape, aka 'Thredtape' with the stove when you're out & about Once sorted these stoves are very good. I have used them at - 13 C without any problems.
If the rod is moving back immediately after you release it I don't think there is much of a problem. Any pump will only push air into where you want it if the pressure you build up by pushing the rod in exceeds the pressure in the reservoir (plus the resistance of the NRV spring). Each stroke puts slightly less air into the tank than the last because as the fount pressure builds the equilibrium point moves further away from the NRV. Once you release the pressure that air is trapped inside the pump. The trapped air can push the rod back until the pressure inside the pump equals the atmospheric pressure plus the resistance due to friction around the pump leather. If your pump is well oiled the rod can come back a considerable distance. If you are still concerned about it you could try removing the rod and watching the NRV for signs of kero leaking into the pump. (Don't try this on a white gas stove). How many pumps are you giving your 96s once you have them lit? If the fount is full it will not take many strokes to get it going and the thermal feedback as the stove heats will largely maintain the pressure as the fuel gets used up. Hope this helps. John
