I replaced the front tube in my 2002 GasGas TXT Pro 280 today as it had a couple old patches from previous owner that didn't look too secure.  It leaked down overnight I believe due to a hawthorne spike.  Odd, second time it has done it in about 6 months and both times I removed this tube and placed it underwater and used soap and found no bubbles.  Rest of the days for half a year it held air fine.  Valve is fine and capped.   I saw a remnant hawthorne spike in the tire so that is likely the cause - I removed the remnant, but didn't see it in the tube.  Anyhow, the new Michelin tube has a dished washer and 2 nuts on the valve stem.  The dished washer I presume stays against the tube on the stem.  Where do the nuts go?  Should one be inside the rim and one outside?  Bike appears to have stock GG rims.  Seems this GG rim is so deeply dished along its center that maybe the tube won't settle down completely into the rim where the valve stem goes through the rim, and perhaps one nut should be inside holding the tube off the rim a bit.  I do have a good beadlock and there has been no torqueing migration of the tire and tube around the rim.  No rim/tube pinches either.  Just figured I ought to ask where the two nuts go.  I saw lots of debate on this on a street bike forum, but those rims are less dished.  Advice appreciated.

I've used both on the inside, one acting as a locking nut. Also had just one on the inside with no problems. I don't put one on the outside in either case, this is to allow the valve to flex and avoid shearing from the tube in case of tyre creep. The high speed risks and loadings may be lower than on a road bike. 

 The two nuts are an anachronism, they were used to clamp the rim between them to locate the valve stem but dirt bikes don't use them and street bikes don't use tubes anymore.

Apart from not using the locknut in order to prevent tearing the valve from the tube due to creep (which happens even with security bolts) you could also elongate the valve hole in the rim to allow room for movement.

My road bike is a modern anachronism that came fitted with tubes.