Kawasaki KZ650 cafe-racer. Engine upgrades. Part 1.

It’s high summer around and shame for me, I could find only a little time for internet.  But silence on my website doesn’t mean that works in my garage are postponed.

I actively work on our new project, Kawasaki KZ650 so that’s only lack of time held me off posting updates.  But today with evening free and some classic rock sound from dynamics I found a bit of inspiration to write out some my thoughts about the project, about engine to be precise. I disassembled engine that I bought in 2011 and found that most of its components are in perfect condition, that’s really rare thing for engine made thirty years ago.  But about it and my guesses about how it happened will be in my next posts, this one is about KZ650 engine performance improvement.

There is a way to increase KZ650 engine capacity up to 810ccm, and if I had “modern” version of KZ650 engine with inverted tooth type cam chain and modern type of cam chain sliders, maybe I would hesitate about such a way of upgrade. But as turned out I have good olden 1978 engine in condition close to new, so it would be blasphemy to treat it in such way.

Thus, I decided to left engine as close to original condition as possible, however it would be not in spirit of gazzz-garage to left it in stock. So here are a couple of my first upgrades. First is Wiseco K700 big bore and high compression piston kit.  I had a pleasure to work with those piston kits earlier; moreover I updated my own Zephyr 750 with Wiseco 810ccm kit some years and more than 70 000 km ago. Zephyr 750 is a very good bike as it is, but Wiseco kit made it much better, especially with some modification of exhaust system, thus I didn’t hesitate to buy this kit for KZ650. It arrived already, so here are some photos:

And as I am about to increase engine performance I also have to make update of cooling system.  And for me, as for Zephyr 750 owner the matter was simple. Once I saw KZ650 oil pan I knew for sure that I could simply replace it with Zephyr 750 oil pan which has ports for oil cooler. And surely, Zephyr 750 oil cooler has performance enough to fit improved KZ650 engine.

Definitely, I checked if the KZ650 oil pump needs to be upgraded. It turned out that part numbers of KZ650 and Zephyr 750 oil pumps are similar. Moreover, that pump is also used in the wide range of Kawasaki motorcycles from 400 up to 1100ccm. That’s Kawasaki Heavy Industries for you. And I have to say I like it!

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