Engine rebuild '79KZ400

I am trying to restore my grandpa's KZ400. The bike has not run in 30 years. I have found a running KZ willing to donate all of its parts to my grandpa's bike. I want to rebuild the engine and disassemble/clean the rest of the bike to make one out of the two bikes. How in depth or difficult is a rebuild? Who can reccomend a place to get the engine rebuilt? Any helpis appreciated.

Better picof my Grandpa's

Cool a kz400 Deluxe, those are neat!

To be honest 400 engines are cheap and plentiful, if the donor is a good runner then just swap out the engine. If not find another one. If you want to rebuild it yourself as a fun project then go for it, but paying someone else is going to get way to expensive for a 400. Also keep in mind parts are drying up for these bikes.

Oh and the first thing you need is the Kawasaki FACTORY service manual, do bother with a Clymer, get the Kawasaki one. Trust me on this there are tons of mistakes in the 400/440 Clymer manual.

One more thing, these small twins are tough engines, they almost never need internal work. Unless there is clearly something wrong, I would advice against tearing one apart.