KZ 900 - 50 years later !

Kaw-boy 900 post=914159 userid=81101How to restore the lower parts of the fork when too polished? Hydro blast?? Can it be made assembled?

hardrockminer wrote:

I do it as Clay mentions, starting with a rough paper, maybe 400 to remove scratches and dents, then finishing up with a high grit paper...2500 to 5000.

   

asphalt900 wrote:

Addressing both issues. First that pesky flooding of bowl overflowing, hopefully not next to your water heater! Like Rolf mentioned, "could" be just some minute crap?? More likely though just worn assemblies. These Brass seat and steel needle assemblies never liked the constant pressure of fuel from the get-go. Especially after a ride, radiant heat from engine under the tank, tends to pressurize and exasperate the problem and/or find the weak points. I always just buy new. Mikuni VM26/26-2.0 or in the later used VM26/26-2.3. They are around 20-25 USD a piece and great insurance. I see a lot of fellas mentioning polishing them with toothpaste and q-tips, that does little good if any. Forks, were they over-polished? Blasting to even the tone of aluminum color/old clear coat removal is the initial step. Ya don't want glass beads for this initial cleaning, glass doesn't "bite" it bounces. I use a fine silica but i.m sure other products/media out there that could achieve the same. Then sanding, this is the part that takes the most time by far. Getting out all those knicks and gouges from years of service. Then polish. After that a scotchbrite pad will give you the "original" like brushed finish. Clearcoat after.     

slmjim+Z1BEBE wrote:

Kaw-boy 900 post=914159 userid=81101How to restore the lower parts of the fork when too polished? Hydro blast?? Can it be made assembled?

   Over-polishing seems to be a thing for some so-called 'restorers'.  It's much easier to do mirror-finish polishing than recreate Mama Kaw's correct OEM  finish with the very fine 'linishing' marks that results in a 'gloss/satin/brushed' look, for lack of a better phrase.  We've experimented with accomplishing correct OEM finish on over-polished and corroded aluminum two ways; both are time-consuming & tedious:

   1)  Wet sanding.  Start with fairly coarse, move progressively finer.  Works well on broad, flat surfaces like clutch covers, gently-curved surfaces like chain covers  & points housings. Time consuming & tedious on compound curves like dyno covers. Move to progressively finer until the target finish is achieved.
   2)  Fork lowers are a special case.  Corrosion occurs under the OEM clearcoat that must be removed with fairly aggressive means.  The OEM linishing marks are more apparent than on most any other Z1 aluminum.  Finishing with more-coarse wet sanding works.  There's another method slmjim experimented with ('cause he's an incurable tinkerer & tool junkie) that worked well on fork lowers:
   There's a type of drill arbor that holds the ~5 1/2" dia. replaceable, very coarse & aggressive, flexible foam abrasive disks intended for rapid paint & rust removal.  Remove the disk from the arbor if present.  slmjim used 3/8" sisal rope for the next step 'cause that's what we had on the shelf, but poly might work as well.  Cut two or three lengths of rope about 6", no longer than 10".  Wrap them evenly spaced around the arbor & clamp in place to make a rotating flail.  Trim the ends to even lengths.
    For abrasives he tried the pumice powder available at paint stores for traction on steps, and also valve grinding compound.  Use vegetable oil to make a thick slurry of abrasive paste to wipe onto the workpiece and also dip the tips of the flails.  Wiping a thin coat of vegetable shortening on the workpiece as a binder & dusting the abrasive on it works too.
   With the  arbor in an electric drill, flail away; outside is preferable.  Wear eye pro.  slmjim sez, "Keep your mouth closed".

   Either method will produce finishes indistinguishable from OEM given enough time & patience.  Neither will remove deep pitting from corrosion.

Good Ridin'
slmjim & Z1BEBE