i have a 67-72 wheel and the valve stem hole is on the drum/sprocket side. ive read stories about chains breaking and busting valve stems. is the issue for rubber stems or metal or both?
It's all great advice. Hoof has a good experience with it not being spit out directly! Ever see one get bound up and destroy a set of Sportster cases when the master link was put on in the wrong direction and was removed by an obstacle in it's path? Doing all of the wheels I've done....quite a sum.....I think 3 were my witnesses to chain aggressiveness disorder. Anything can happen-Don't worry so much about the stem-keep your eye on the chain, it's tension, and it's wear as well as sprocket wear/alignment. Never use a chain/sprocket setup smaller than the series rated for your machine (I.e. 530, 630 etc....)Easy, do your chain maintenance and it will never break.
And if it did break, under power it is going to be pulled straight forward into the gearbox sprocket area and thence to the ground, at a very rapid rate of knots.
How it could possibly thrash around sideways and catch a valve stem is difficult to envision.
And if it did thrash sideways, through some miracle of Murphy's Law to the Enth Degree, what are the chances the paths of the rapidly moving chain and rapidly moving valve stem would intersect?
Forget the urban myths and leave your wheel as it is.