there are a couple of different master link designs for cam chains. There is a press fit one and one where you rivet over the pins to hold the side plate in place. I have used both on my race bikes that regularly see redline and then some and have never had a problem.
I would go ahead and replace the chain while you are at it though and make sure that you buy, or get with the chain, the proper masterlink.
CB350F cam chains aren't real easy to find, but you can find ones for the CB750 for less than $30. The chains are identical to the 350F ones except that they are about 10 links longer.
Cut the existing chain with bolt cutters, safety wire the new chain to the end of the old one and pull the new chain thru as you pull the old one out. Then you can lay the two ends of the new chain across the sprocket and figure out exactly how many links to remove. Grind the pins off and pull the side plate off and you now have a shorter chain.
Tracy