YES. but very LITTLE is normal.
The 350 Chevy does not have a belt, it has a chain. Slack in the chain is normal as long as it is not excessive. A better determining factor on when to replace the chain, is the condition of the gears and if the chain is noisy.
The factory timing chains have a lot more slack than the aftermarket chains.
About 3 degrees of crankshaft movement, or less than 1/4" if measured on the chain with one side held tight.
slack of the chain
it should have 1 inch to 3/4 inch slack in it
You don't. The YFM225 uses an automatic chain tensioner that helps to take up the slack on the cam chain. If you are getting chain slap, then either the chain is stretched or the tensioner is not functioning correctly. In both cases, the parts should be replaced. You cannot repair a non-functioning auto tensioner, nor can you remove links from a stretched cam chain.
Half inch to an inch of slack in the middle is just right.
If you're asking about the timing chain, I've seen factory chains that had a lot of slack, perhaps 1/2" in each direction. Most aftermarket chains seem to be much tighter.
Check for excessive slack in the timing chain.
From the middle of the 2 sprockets you should have about an inch of slack or play in your chain when you lift up on the bottom of the chain with your finger if it looks a lot more then that adjust it but you don't want it to be too tight.
replace the chain and gears
When was the last time the timing chain was replaced? I bought a 1991 Toyota pickup that had 190,000 miles and the original timing chain. Due to the high miles, the chain had stretched which caused a lot of slack in it. This slack allowed the chain to rub the timing chain cover causing a hairline hole/crack in it. Antifreeze leaked thru the crack and filled up the oil pan. Good luck... This is a typical sign that you may have blown a head gasket(s).