Lead replacement or not?

Previous owner told me to ad lead replacement to the gas (98 oct) on my Z650 B1 1977. When looking in the owners manual it states “lead free” to be used. 

What is your recommendations?

Lead is not needed.

These bikes have hardened valve seats so leaded fuel is not needed.
Just avoid high ethanol content fuels which react with the rubber/nitrile carburettor and fuel system components.
Ethanol resistant Viton replacements should be installed if using high ethanol fuels.
 

No disrespect to zed here but nitrile O-rings are designed to swell up with gasoline exposure, thus improve the sealing.  This swelling may not be ideal for all rubber applications, particularly the choke plunger seals, but it's not a problem for all the various O-rings.

I've owned my 1977 KZ650-C1 since it was new (more than 44 years; 62,000 miles) and have always run unleaded gasoline.  No problems.  Ed

 

Unleaded is fine. Ethanol free is best. 

87 octane works better than 98 octane on a stock bike, forget the lead

wrote:

Previous owner told me to ad lead replacement to the gas (98 oct) on my Z650 B1 1977. When looking in the owners manual it states “lead free” to be used. 

What is your recommendations?

The octane rating standard varies between in different parts of the world so you need to keep that in mind when comparing.  For example, 98 octane fuel in some parts of the world would be equal to 91 in other parts of the world.   en.wikipedia.org/wiki/Octane_rating

For a KZ650 all you need is what's considered "regular" gasoline.  As mentioned by others unleaded is fine.

Great info, thank you everyone!