As mentioned, the lead was used to cushion the valve when seating. The biggest difference between engines designed for no-lead and older leaded fuel engines is that the no-lead jobs have hardened valve seats.
You can buy lead replacement, but to buy actual tetra ethel lead is something else. That stuff was on EPA's bad boy list 30+ years ago and sometimes you can find it for racetrack use only, but it's still expensive.
One of the biggest fears of using no-lead in leaded gas engines was valve seat recession. I've used no-lead in Dodge truck, Chrysler powered combine and tractor engines without hardened valve seats with any problem. However, I did have a 2nd combine with a Chrysler engine that had one exhaust valve on each side that had recessed considerabaly. I'd been using the lead replacement stuff in that engine, so you probably know my opinion of all that snake oil stuff stores sell.
As far as bikes go, my '79 KZ1000 ran for 110,000 miles with only 2 valves ever needing shims changed. My advice? Unless you're on the drag strip, don't worry about it. Gas up and ride. If something is going to happen, it's going to happen whether you worry or not, so don't let it bother you.
|