1984 KZ550F Shaft EFI Conversion

Hey all,

I'm a new member to the forum but a long-time lurker. I've used this forum to help me get my KZ550 to where it is now and the community here has already taught me so much in the past couple of years.

I'm a 5th year mechanical engineering student and am currently working on converting my shaft drive KZ550F to fuel injection. I initially bought the bike for a cool $600 as a naive 19 year old with no experience working on NOR riding motorcycles. I've ran into tons of problems with getting this motorcycle in better mechanical shape, and only got the motorcycle tuned and finally running well in February after at least 3 years of sitting.

Below I'll throw a list of items I've addressed on the bike and throw in some pictures I have.

• Replaced steering stem bearings (fused when bought the bike)
• Rebuilt carbs completely
• Changed oil with Rotella T6 and new Hypoid gear oil for driveshaft
• Rebuilt petcock TWICE before abandoning stock petcock and using gravity feed replacement for now
• Rejuvenated air box rubber boots
• Replaced spark plugs, found that previous owner cross threaded into the head. Ordered keensert from McMaster-Carr and replaced one thread very carefully, while other thread was successfully chased using tap
• Identify two spark plug leads with wires fused with rubber insulation, causing no-spark situation. Replaced leads and checked that all coils and plugs worked well
• Replaced physically oversized battery PO installed which pushed entire air box/boot assembly roughly 1/2" forward
• Cleaned/rebuilt left handlebar controls, fixing blinker functions
• Rebuilt ignition switch
• Installed LED front turn signals to accommodate new bars
• Installed Renthal low street bars with Renthal single compound grips
• Used acetone to dissolve failed tank sealant. Used vinegar and BB's to clean tank (needs to be redone, will take to radiator shop next time)

I've attached pictures of the bike at a few points over the past few years, but am still learning how these posts format. Hopefully they're oriented correctly.

Switching gears, I'd like to talk about why I'm doing this project, and the documentation to come.

I'm doing this conversion because I love how unique my KZ550 is. I have a more modern fuel injected bike and love the reliability it provides but feel it lacks some of the character my KZ has. My end goal is to have this bike start up and work flawlessly as a daily rider. While fuel injection could potentially give me small fuel efficiency and power advantages, I'm more so interested in the project to modernize the bike as a whole. My goal is to first get the bike running on a micro squirt and tuned well. From there I'll eventually install a Motogadget m-unit and new wiring harness and edge further into cosmetic mods (waaay down the line). My highest priority is to make this a fun, reliable rider.

I've seen a fair amount of higher displacement EFI conversions and think that documenting my 550 EFI can help others who might be interested, as well as documenting some of the quirks or unique problems I might face with this bike. My older brother is also a mechanical engineer and he is doing an EFI conversion on one of his 1980 KZ440's in parallel to mine. He'll be posting a forum thread dedicated to that bike project soon, and we'll probably be frequenting each other's threads. One of our shared goals is to have video documentation of the process on each of our bikes as well. We've made a Youtube Channel named "Classic EFI" where we plan to modernize our growing fleet of vintage bikes. I'll post a new message with the YouTube link to the video counterpart of this post sometime in the next few days.

Additionally, my next lengthy post will be an overview of my current parts list and custom parts designed so far.

Welcome aboard! This should prove interesting. I have a philosophical question.
How far down the modernization trail can we go before we lose that KZ character?

Hey TexasKZ!

Thanks for the reply! You have a great question there.

How far down the modernization trail can we go before we lose that KZ character?

I think the character my bike has is mostly tied to the time I've put into restoring it to a proper running condition. It also comes from how unique the shaft drive is (made only in 1984) and some of the visual history the bike had when I bought it. It's pretty low mileage still (around 18k) but has a few military base stickers on front forks from the mid-90's. I used to be attached to the idea of keeping this bike as close to factory as possible, but have since changed my mind. My bike will never be a show bike and its imperfections/oddities add to my appreciation of it. I have no issues with suspension, brakes, transmission, engine size itself, or any other cosmetic items on the bike right now.

By modernization I like the idea of changing "what's under the hood" while keeping everything else stock or pretty close to its condition now. The M-unit allows some cool features like alarm setups, electrical monitoring, diagnostics, and key-less ignition which immediately appeal to me as potential add-ons way down the road. One reason for the conversion is also the difficulty I've had with sourcing TK-26 carburetor parts. At this point I've already spent a considerable amount on replacement NOS carb parts that had previously croaked on my bike. Running popular OTS components or assemblies that I can still source cheaply and easily is really appealing for my future maintenance of this bike.

Once I have some of those features on the bike in addition to the Microsquirt setup running reliably, I'll be pretty happy with that for now (famous last words). This bike isn't meant to be a racer or anything too crazy, It's just got a soft spot in my heart after the few years I've owned it. I'd like to invest my time now before I graduate and ensure that it runs great for a long time.

As promised, here's a brief YouTube video walk around of the bike as it stands right now. I've bought a few of the EFI components but am currently waiting on some 3D printer upgrades in the mail. Once those are installed, I'm going to validate a few of my designs and do a proper write-up/video covering them. In the meanwhile, I'll be adding another video to the channel in the next few days which covers the carburetor and points/advancer removal.



Lastly, I also purchased a KZ550-M1 factory service manual when I first bought the bike. I recently digitized it with a phone scanner app because I haven't found any copies of it online. I tried to attach the PDF to this post, but since the PDF is made of images the file size is quite high at 83 MB. It has some issues with colors, but has text recognition and is searchable. Attached is the link to view/download.

drive.google.com/file/d/1MD2vV-tYJPEcch-...OuG/view?usp=sharing

How far down the road is a bit like the which oil question. Some will start twitching if there is a single aftermarket washer, while others will say it takes only a single factory washer to preserve the character. I guess most of us swim around in between.

There is a special place on KZR fir digitized manuals. It is under the Articles tab. You may need a moderator to load it. Generations of 550 M fans will sing your praises.

Thanks for the tip! I'll get in contact with a mod and make sure it gets up there for more visibility!

Hey all,

It's been about a week since I last posted. Since then, I've filmed and uploaded another video (linked below) and am diving deep into some of the designs I have to make. 3D printer upgrades for nylon printing have arrived and I'm calibrating the 3D printer characteristics to give me the most precise prints possible.

In the video, I go over the KZ550 teardown. I remove the fuel tank, carbureors, air box, and electronic ignition. Later tonight I'm posting my lengthier parts list description, and later on I will release a forum post and video specifically going over my design process for the custom components I'm working on.

Alright everyone,

It’s time to discuss my parts list for this build. First off, I’ll be using the Microsquirt module from DIY autotune running batch injection and a wasted spark setup. From my understanding, the Microsquirt module can only handle two fuel injection batches. Installing another VR sensor or hall effect sensor on a modified cam cover wouldn’t be worth it for sequential spark over a wasted spark setup.

I’ve already bought a set of 2013 zx-6r throttle bodies from Ebay. I chose these throttle bodies because thy were a good deal at $35 shipped with all sensors and fuel rail included. It seems like most modern 600cc throttle bodies have a 38mm ID, and I’m adapting to a 30.5mm ID from the TK-26 carbs on this motorcycle. The biggest issue with using modern throttle bodies is the difference in timing chain/sprocket locations. On the KZ550, the cams have centered gears with chains for timing, whereas on newer bikes the cams are almost cantilevered and are driven from one side. For this reason, the throttle body spacing must be adjusted to more closely fit the KZ550.

The 2013 zx-6r throttle bodies have a 73mm center-to-center spacing, with a 53mm OD. The KZ550 has a 71mm center-to-center spacing for the outer two-cylinder pairs, and a central spacing of 91mm. The 2mm spacing difference between the throttle bodies and kz cylinder will be accounted for within the adapter fitment. The throttle bodies are going to be split and spaced 18mm to account for the extra spacing needed. The throttle bodies will have other custom parts on them which I will cover in more depth on another post in this thread.

To jump back onto topic, I’ll throw a bulleted list of parts for this build.

• Microsquirt w/8 ft harness
• GM Open element IAT with pigtail (Intake Air Temp sensor – used to calculate air density)
• GM Closed element CLT/IAT with pigtail (Coolant Temp sensor – in this case used to measure heat fin temps)
• LC-2 Wideband sensor with controller (Senses air/fuel mixture – will be welded into midpipe)
• TRX-420 fuel pump
• Zx-6r Fuel Hose (for connectors)
• 2008 zx-6r crank trigger sensor
• ¼” Black Buna-N Nitrile Fuel line (sold by foot)
• Custom 36-2 trigger wheel
• Custom 2-piece TB to head adapter boots
• Custom fuel return tank fitting which will replace the low fuel sensor tank opening. My bike has never had the sensor so no loss there. This will allow fuel to circulate from one side of the tank to the other and minimize localized heating.
• Bent sheetmetal mount for GM closed element head temp sensor. (Hoping for no fin drilling)
• New Throttle cable
• Custom TB spacers
• Fuel rail extension/replacement
• GM open element IAT sensor mount within TB split
• Various solder seal wire connectors

I feel like most of these are straight forward, but I’ll comment on the fuel pump and crank trigger selection. The TRX 420 seems like a great choice because it has an integrated pump, filter, fuel pressure regulator, and a small swirl tank. At around $130 it seems like a nice option to get the bike running. I’ll probably switch it out later for a Wahlbro pump and more specialized setup with the goal of saving space, but this pump should work fine for now. Digging around some other forums, it seems like this pump also only draws 1.77A during priming, which would be impressive if true. Most modern 600cc class fuel pumps have a constant draw of around 5A and pull as much as 12A during priming. My factory stator puts out 18.5A at 10k rpm. The trigger sensor was just a great deal from eBay. Scored it for $20 shipped. I have no specific brands I’m choosing to use for components, I’m just choosing based on which I think would work best for a reasonable price. Components that have documentation in others builds are always a plus, which is why I’m buying most of those components from the DIYautotune website itself.

On my next lengthy post, I’ll take a deeper dive on the design process and some of my prototypes. I’ll also talk about my material choices/manufacturing methods for some of the components (and include pictures).

That's quite a project you have going. It will definitely be interesting to watch the progress.

I usually see 92 mm as the spacing between the inner ports (2 and 3) on Kz550's. That holds for several other bike lines as well, like the Zr550, Zx600, and even Zr7.

I usually see 92 mm as the spacing between the inner ports (2 and 3) on Kz550's. That holds for several other bike lines as well, like the Zr550, Zx600, and even Zr7.

Thanks for the heads up, Loudhvx! I'm currently using the cheapest harbor freight calipers and wouldn't be surprised if they had a 1mm error near the end of their measuring length (or operator error). All the more reason to invest in some properly calibrated Mitutoyo calipers!

Hey all, it's been about a week since my last update. I had originally planned on describing my overall design process in one (thorough) post and an accompanying video, but most of my time in the past week has been designing and prototyping custom throttle body adapters. I'm designing adapters that will perfectly fit both the 2013 ZX-6R throttle bodies and engine block, without needing any other processes. I'll use a nitrile rubber strip as a heat break between my nylon 6-6 parts.

Anyways, I've designed and iterated 5 versions of the adapters so far and am hoping that V6 will be the final iteration. From there I'll write up an in depth forum post explaining what problems I fixed with each iteration and showing the final design on the bike. I'll make a short youtube video to accompany it as well.

For now, enjoy these photos and captions of some prototypes so far.


V5 models on my mock intake in Solidworks. They're each a slightly different design here to account for TB spacing.


V3 mounted on bike to verify the retention ring design worked to hold the throttle bodies securely.


That's the perfect fitment I'm looking for.


Had to increase height a few millimeters to ensure Allen wrench clearance.


Offset hole design to perfectly fit on throttle bodies. In V6 I'm accounting more for injector flow and will be modifying some of the interior.


V4 solved all throttle body fitment issues, but forgot to account for the 2mm spacing difference between the ZX-6R throttle bodies and the KZ550 intake spacing.


(Not directly) Top view of V5 models. I added numbering to easily orient and identify the adapters.


Fronti view of the adapters. If you look closely you can see each of the larger ID's is offset 1mm in either direction to directly adapt the throttle bodies.

3AM update: V5 spacing is a success! First look at Left bank of throttle bodies fitted to the bike.