KZ650 cafe-racer

Then I cleaned the insides of end covers, sealed them and proceeded with outer sides.





I could have them polished, but the general idea was to make them look “new stock” so I just refreshed them. As you may see, I removed the output shaft and bearing to clean the end cover through and out.

I checked and maintained the armature (rotor) by the book. Here is how my improvised holder for rotor looked :



After cleaning it looked nice. Brownish coating on it is varnish.



Input terminal of field coils also needed attention.



I cleaned it and removed protrusion of solder.

Before I could start assembling the starter motor I had to replace bearing and O-rings. Since O-Rings have part numbers it’s not an issue to buy them.



The bearing of the output shaft is 6003Z bearing. Letter Z or 2Z or ZZ in the end of the ball bearing name means that bearing is equipped with metal shields from both sides (sometimes single Z stands for shield from only one side).



The KZ650 starter bearing looks like it was intended to have two shields (there is a groove for the second shield), but had one of the shields removed. It is very important that it has only one shield.



The fact is the KZ650 starter has oil seal placed right over the bearing. The only bearing shield faces the outer side of the starter cover, and since this shield is non-hermetic, during the work of engine oil mist penetrates it and feeds both: bearing and seal.

Thus, this bearing couldn’t be replaced with RS (equipped with seals) type of bearing. After some thoughts I chose NSK 6003ZZ C3 bearing. C3 stands for additional radial clearance, thus such bearings are more suitable for high temperatures.

After I removed one of the covers and washed out grease, the bearing was ready to be installed.



As I wrote in a previous post, KZ electrical starters are equipped with three gaskets that have no part numbers and thus couldn’t be ordered. One of them is most significant. I will explain why in the next part of the story. I measured what remains from old gaskets and places where they have to be installed. On the base of these measurements I drew blueprints for gaskets and then ordered them to be laser cut from Gambit AF-OIL gasket sheet (based on Kevlar® aramide fibres, mineral fibres, and fillers bound with NBR rubber-based binder). As I wasn’t sure about gasket thickness, I ordered two sets of different thickness.



To assemble yoke assembly I had to refresh screws that mount field coils’ poles. That screw is pretty specific M6 countersunk screws, as they have heads of diameter smaller than ordinary countersunk screws. Here is original screw in comparison to stainless steel Allen screw:

I decided that stainless steel screws will fit such an application, so I modified four of them to replace original screws.





After this everything was ready for assembling. I decided to not replace the original oil seal: for one thing it looked completely intact and for another it has quite a specific configuration of what is in ordinary seal is dust lip. But before I started assembling, sure, I couldn’t but shoot the exploded view of the starter motor.

gazzz wrote:

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Your attention to detail and these photos of shiny stuff laid out neatly keeps me coming back Nice work gazzz!

Thank you!

Wow.. that's dedication for you right there... This makes me feel guilty about taking my starter motor for granted and now i feel obliged to do the same. Thanks for the detailed post and good job.

Thank you! Let's continue the story.

I started assembling the starter motor from yoke assembly. As I already mentioned, Kawasaki service manual indicates that “is not meant to be disassembled”. The reason is simple: the gap between rotor and field coils’ poles is quite small. Thus poles have to be positioned strictly straight along the stator housing and to be parallel to provide that gap. And since we figured conditions of task’ successful fulfilling, yoke assembly’ assembling became a matter of improvised “special tool”.



When I put the assembled part on the table and took my camera to shoot photos, I couldn’t help remembering Nietzsche quote: “And if thou gaze long into an [strike]abyss[/strike] yoke assembly, the [strike]abyss[/strike] yoke assembly will also gaze into thee”…



Next task was output shaft assembly.

I greased the shaft with high temperature grease, oiled bearing and seal and then drove the shaft into position.



Then I fixed it with a circlip.



After that there was time to put the first “narrow” gasket. This gasket along with its twin seals inner gear chamber.



I greased inner gear and planet pinions with high temperature grease and installed them. One may find different opinions on the subject of how much grease has to be applied to this unit. My personal opinion (based on experience of starter motors servicing) is it has to be a moderate amount.

Once I finished with packing one end cover of the starter motor, I turned my attention to another. I installed brash plate on yoke assembly:



Then I greased the thrust washers, put them in the original sequence (just note it when disassembling), greased the end cover bushing, installed the rotor into the yoke assembly and closed it with the end cover. Then I put another set of thrust washers in the right order on to the rotor shaft and was ready to put the end plate in place. I did operations in such order only to demonstrate significance of “wide” gasket. Take a close look on these photos:

As you may see, the starter motor positive intake terminal (copper bolt) is positioned extremely close to the groove in which the end plate has to be placed. And since the end plate is made of steel, such a close neighbourhood of positive intake to the steel part which contacts with “ground” may end up in sparks. So the third starter motor gasket is in fact an isolator. That’s why it’s wide and that’s why it is inadvisable to assemble the starter motor without it.



After end plate and second “narrow” gasket were installed, the starter motor was mostly ready:



All I had to do was to finish the job as to install another end cap with gears in it with assembling marks aligned.



Screw two bolts and install starter motor pinion. Just don’t forget to install it with chamfered teeth facing out.