1974 KZ400 engine rebuild: silicone use?

Good morning all.

I have a 1974 KZ400 that i am doing an engine rebuild on. The engine had 9700 original miles. It was sitting in indoor storage for almost 25 years before i got it. The bike will be receiving new gaskets/seals from the cylinder base O-rings on up.

When i took the engine apart, the original head gaskets and valve cover gaskets were heavily coated with some type of silicone sealant. The head gasket is the "flat" type with copper rings, the valve cover gasket is a large O-ring type.

In my manual i don't see any reference to the use of sealants when rebuilding the motor.

Is silicone necessary on the rebuild? Or do the gaskets go in "dry"?

Put them on dry. If there was silicone on the gaskets someone has been in there. The factory did not use silicone on the gaskets, and in fact, using it is a bad idea as some can break loose and clog oil journals. Ed

If not already done, would have the head checked at an automotive machine shop to assure that it's level, and if warped, have it re-surfaced.

If the head is warped, the head gasket will probably leak, regardless of how much sealant or type of sealant is applied during reassembly.

Good Fortune!

Early model KZ400 top ends leaked like a sieve. I had them start leaking oil on their 5 mile pre-delivery test rides!!! I chuckled to myself when I read about all the silicone on the head gasket. Dealerships were trying everything in the book to seal those motor from leaking!!

Kawasaki came out with a "top end sealing kit" it had a newer style head gasket, and a BIG tube of a white sealant like TB-1211. I think it had shorter cylinder studs too. The main problem was the crowned cylinder stud nuts bottomed out on the top of the stock stud before the proper torque was achieved. Kawasaki did away with the O-ring between the cylinder head and the rocker arm cover, and told you to fill O-ring groove with the sealant.

On my 750/4 the factory service manual calls for "liquid gasket sealer" on specific locations of the head gasket. You don't normally use sealers, but you might want to check the service manual for any specific references.