Tire casing wore hole in tube

I have seen this in the past. It was due to two things.
1. Very low tire pressure.
2. Tire slipping on rim.

A bad or loose rim lock can also allow the tire to move on the rim.

Paw Paw

Baby powder is your friend. Make sure when you put the new tube in it's all clean and dry. Apply a light coat of baby powder inside the tire and rub some on the tube.

For serious racers, I always used to feel the inside of the tire for manufacturing "defects" like this. There were several times I took a razor blade and scraped the inner casing to provide a smooth surface.

It's cheap insurance when you're at a national or a serious race.

Nowadays, mousse inserts do not suffer from those conditions.

I know paw paw has seen this in the past. When I first got my first cr 250 in 1985 (a used bike in early 86) every time I made a lap the rear tear would go flat. We tried everything we could think of and finally put a new rear tire on and it stopped . The tire that was on there wasn't very old and the tread was still great that's why we tried other things first, but it definitely had a spot in it that would pop the tube every time you rode on it....