KZ650 Performance Project | 1

If you’ve ever taken a look at a KZ650 and researched its history you will know that it was produced to be faster, lighter, and more powerful than any other 650 and 750 during the mid-to-late 70’s.  For that reason I had desired this bike for awhile.  I spotted one on craigslist for $500 and jumped on it.  What thrilled me the most over the course of this project is what had been discovered inside the engine.


It was found in a shed sitting for over 15 years.  Naturally some things would be wrong with it.  It had dry rotted tires, a frozen master cylinder, oil leaking out of the engine halves, ugly decals, and a hideous sissy bar.  First things first, lets make sure it runs.

GOOD LORD!  That’s certainly not the sound of a stock engine.  Later on I had discovered this KZ has been highly modified with 65mm pistons (+3mm over stock), Andrews #20 Cams (.350 lift vs .304 stock cams), and a Martek 440 electronic ignition system.  All of which screamed to the tune of a Kerker 4-1 exhaust.  It was now time to tear down the engine, frame, and rebuild her with some additional performance upgrades along with a new look.


Opps I managed to chip the piston wall during removal of the circlip .  This is going to suck.


It’s just my luck that Wiseco no longer makes the 65mm kit.  Instead I had to take a small step backwards if I was going to stick with the Andrews Cams.  So I purchased Wiseco’s 64mm kit and a used stock cylinder block on eBay.  Cylinders were bored out by PowerSeal USA and fitted to the new pistons.  Since this is Part 1 of this project I am still working on reassembling the engine.  At this point I continued with the tear down of the motor.


Lucky me, more upgrades!  Those are performance springs installed on the clutch.  I couldn’t be happier.

clutch springs

With the engine torn down I began the restoration process.  First with vapor blasting the engine.

KZ650_vapor blasted

Following that I had the frame and miscellaneous parts powder-coated.  This was my second time using Prestige Powder Finishing in Newark, Delaware.  They primarily work on industrial contract jobs but they will do frames on the side.  Here is the before shot.


And here is the after shot.  The finish is ‘Satin Black’.


The head was rebuilt by MAR Automotive.  Thanks to Ed for the recommendation.


The dirty carbs kept bugging me so I gave them a good wash using an Ultrasonic Cleaner and Simple Green.  Clean on the left, dirty on the right.


Keeping in mind that air-cooled bikes are not particularly fond of hot summers and stop and go city streets I thought it would be proper to add an oil-cooler to the KZ650, especially with all this extra heat I’ll be packing.  Oddly enough there is a simple solution.  A direct oil sump swap from a 84 GPZ750.  You’ll notice the exchange for the oil cooler at the top.  KZ650 on the left, GPZ750 on the right.


Time to get back to the frame and wheels.  Black spokes, polished hubs, and Avon Roadrider for tires.


I replaced the fork seals and added performance springs with 15w fork oil for better dampening.  I also added a Tarozzi fork brace for better handling.


I continued with handling upgrades by installing Progressive Suspension on the rear.

KZ650_rear sprocket

The KZ650 stock sprocket sizes are 16T on the front, and 42T on the rear.  I’ll be running 17T, 42T.  This will drop the RPM’s 1,000-1,500 while cruising on the highway.  I’ve heard the stock setup revs high at 70mph and this should help with that.  At this point I am glad the KZ is finally standing on its own again.


I am using a KZ900/1000 front fender.  It looks better and wraps around the tire to prevent slinging rain and rocks.  Aesthetically you’ll notice I blacked out some pieces and added black euro style handlebars.  I also added LED turn signals.


I found a rough design for a Fender Eliminator on a KZ650 forum.  I purchased an aftermarket LED taillight and began drafting up a template.

FullSizeRender (2)

I then tried it on for size.  Once I get the fitment right I’ll then go ahead and fabricate the final version.

KZ650_Fender Eliminator Test

Currently this is all I have to share at this time.  I am in the midst of polishing my engine covers.  I hate polishing at times but love how it looks in the end.  Philadelphia’s own Bill Becker has agreed to assist me with my engine assembly and after that I should only require a fresh paint job.

Hope you enjoyed reading this.  Stay tuned for Part 2.

13 responses to “KZ650 Performance Project | 1”

  1. Adam says:

    Looks awesome Ted. Jealous that you had cams in there already. Did you find any more specs on that cam profile?

    I also swapped to the GPZ oil pan to the run the oil cooler. How do you plan on mounting the cooler?

  2. Ted C. says:

    Thanks. I reached out to Andrews and they actually dug around some old catalogs and sent me a scan PDF of the cams they used to sell. Here’s the link.

    To mount the oil cooler I thought about two options. First option, build a bracket that attaches to holes where the horn is mounted. Second option, move the tabs on the cooler to fit in the holes where the horn is. The cooler is aluminum so I am not sure if welding those tabs on and off is a good idea.

  3. Ed says:

    I’m into it Ted.
    Spring 2016. KZ drag race.

  4. Pat says:

    Good luck with it, looks great so far.

  5. Alex V says:

    Looking really good! Really digging where the engine mods are going. I would like to join this KZ race.

  6. Ted C says:

    @Adam @Ed @ Pat @Alex
    Thanks guys. I need to find more time to work on it. Seems to be the major hurdle right now. I will keep dig at it slowly and surely.

  7. […] Project.  Truthfully I just took my sweet ass time while still being anal about every step.  See Part 1 to get caught […]

  8. lonny self says:

    pretty cool,stuff was looking around for motor stuff hit your sight just picked up a barn find 77 650 for free she seized up but will see everything is there little rust but not bad was covered last 14 years in a garage last ran in 84 or at least the tabs say funny thing guy across the street from the place I picked this one up guy asks if I want his 81 550 ltd for free looks like same treatment but is in way better shape with windjammer still on it mostly dust carbs still throttle and it is not seized so thinking crazy 550 cafe and a bone stock rebuild on the 650

  9. Chris says:

    wanna sell that bad boy ted?

  10. Joe says:

    I have no idea when anyone last replied on this but I’m looking to install the larger pistons, is it essential the cam needs to be changed to do this ? And can the larger pistons be installed onto a standard z 650 Con rod ? Thanks

  11. Ted says:

    @Joe the larger cams aren’t necessary. On my cams you don’t really notice the power until you are above 6k rpms.

  12. Bruce Gilbaugh says:

    Ted, Where did you get your fender eliminator fabricated? Between the fitting diagram and the final product in your last picture boggles my mind. It is absolutely beautiful and you didn’t have to cut the frame.

  13. David says:

    This is Biggpappabear2 and I have a kz650 and got the last big bore kit form the 80’s. That will make it 830 cc but I can go to 880 and maybe 900cc with titanium pistons and beryllium rods and maybe beryllium pistons with roller crank and cams and transmission bearings. Add twin turbos and watch out.

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