I got a really good deal (FREE) on a Mattel ride on Caterpillar dump
truck for my son at a garage sale. It had no markings or battery, so I
popped in a 12V motorcycle battery. When I switched it on, I heard two
pops from the back of the vehicle. I think that I burned out both
motors. So now I'm looking for replacements.

Since my quest began, I've learned that this toy takes a 6V battery to
drive both motors. I guess this explains the "pop" sound and confirms
my theory of the motors being blown.

Check the fuse. There's always a *small* chance that it popped before the
motor did!

steve