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Leaky Dunlop valve
#1
I've got a cute little Japanese Asahi bike that I am told has Dunlop type tire valves. The last time I filled the tires, using a Presta valve adapter and an air pump, everything went OK with the tire inflation, and there were no leaks after filling. This time, the front tire inflated just fine, but the back tire leaked air constantly from around the valve and its attached adapter, and when I unscrewed the adapter, the tire rapidly deflated to the point of flatness, and even with the cap on, there was still the sound of leaking air. I did remove the pin inside the valve after this, since it slipped out very easily. At the base of the pin, there appears to be a small rubber gasket that looks intact, as far as I can tell. The small flanges on this pin fit right back in the grooves on the valve stem, so I don't think I disturbed the pin that much. I tried wetting it down with a bit of spit, but when I attempted inflation again, the same thing happened.

I really don't know much about these valves, and I can see why they wouldn't be very popular. What I'm wondering is if I can fix this valve myself, and I'd appreciate any input. Fixing this myself would help me avoid ridicule from the local bike shop guys who would much rather sell me something new than fix anything. Thanks for your advice!
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#2
OK, main problems with Dunlop valves are valve not seated correctly (the nut is loose) and a damaged rubber tube (though they now use a different technique). As both things seem to be OK, you can try replacing either the rubber tube (might be porous) or the complete valve. If that doesn't help replace the inner tube. Spare valves and the little rubber tubes used to be included in most patch kits here (at least in Germany). This kind of valves is now a bit less popular, I guess because you can refill tyres with Schrader valves at the gas station. Dunlop valves had the advantage that they were simple and you could replace them very easily. People used to patch the tyres so the valve had to last for quite a while, nowadays many just throw the tubes away after a puncture.
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