Bicycle Mechanics - Fit a 20" tube in a 19" tire?

I'm currently restoring an old Solex 3800 (a motor-powered bicycle) that has a strange wheel size- 19". Will a standard 20" (BMX) tube fit in this wheel? Here is a pic of the bike-

http://images.forum-auto.com/mesimages/304137/solex-3800g.jpg

I think it might. Assuming the pressure is low, just be extra careful not to have a kink in the tube.
The cost will be low, so it's worth a try anyway.

The difference in diameters of so-called 19" or 20" tires is not necessarily 1". See these charts for actual diameters of the bead-seat diameter (BSD) of the various tire standards: http://sheldonbrown.com/tire-sizing.html

I don't see anything listed as 19" specifically. I would estimate the 19" wheel's BSD and see how it compares to a 20" BMX wheel (406mm I believe).

The only tubes I've seen that are compatible with two different standards are ones for 700c (622mm) and 27" (630mm).

That all being said, if it fits, I guess it fits.

You should be able to use a 20" tube. I once found a tube inside a 27X1-1/8 tire that was about 6 inches longer than a standard tube. it had a 3" section that was folded over itself, and I never knew about it until I changed the tire. i don't know where that tube came from. I also heard of a guy who drilled a second valve hole in his rim and put 2 tubes in the same tire. If he had a flat, he just pumped up the other tube. I never actually saw that, but I think it would work.

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Try stopping by a place that sells scooters or mopeds. I bet they have 19" tubes.