TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. > Project Classic Motobricks

K75s midlife refresh

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starting a project thread rather than keep posting in "what did you do today" area...

the original pics when i got in sep15

about 35k miles.

seat is a Corbin "rumble seat".  flip up back rest.

did compression check
temp fixed cracked crankcase breather hose (new one on the slow train from maxbmw)
TB's synched
choke and idle adjusted

then added new lic plate, not very original, but...

matches this one in seattle, owned by brother..

moved it to the shop for some maint..

first up...spark plugs.  same plugs as an S14.
old ones not too bad, but had been in there a long time.  the caps that go into the wires were totally corroded.

noticed one of the reasons the idle may be off, cracked crankcase vent hose...unmetered air going into airbox.

main airbox to manifold hose needs replacing also.

on to the brakes...full fluid flush front and rear.  this had not been done in a while either.  no way to use a pressure bleeder, but you can squeeze the brake lever/pedal with one hand while working the bleed valve with the other.  ez.  Moto MC's sure don't push much fluid.

rear abs

rear brake

front MC on handlebar

nasty old fluid

then took the "barbacks" off.  these aftermarket devices move the handlebars up and back about an inch and a half for a more upright riding position.  not my style.


then i changed the final drive oil to redline 75w90 and the transmission oil to redline MTL.

everything is so small!  not used to working things other than cars.

i understand the need for motorcycle lifts now though.  even sitting on the floor it is a pain in the knees and back to work on this thing!

will get to the throttle body adjustment next.

removed every light fixture front and back, cleaned inside and out, cleaned all connections, replaced all bulbs with new and tested.  it is amazing what just this simple maintenance does for brightness....on a bike or a car.

found that a PO had done an early upgrade to make the tail/brake light more visible.  changed all the bulbs and sockets to use dual filament  1157 bulbs.  took me a few minutes to figure out the wiring and compare to shop manuals to see what was going on.

these were actually added lights in an unused part of the tail lens for the brakes.

and of course, while i was in there, i added a Skene Design P3 rear LED light.  light is a "third brake light" that flashes on brake application, then goes solid really bright.  it is also an always on tail light at lower intensity.

I also have a Skene "photon booster" amber LED setup i will be installing on the front forks.  Visibility is a good thing!

started replacing the alternator drive bushings.  ya gotta take a bunch of the middle of the bike apart to pull the alternator out.

it is buried down deep.

here are the rubber drive bushings which in K bike slang are called "monkey nutz".  here is alternator side.

these look original to the bike and are dead. there are no belts to drive the alt.  the alt is drive by gears through two three pronged couplers with the monkey nutz absorbing the shock between the two.


here is the engine side of the coupler

finished the alt bushing replacement.  of course had to paint all the parts that were removed.

after changing the dead monkey nutz, made a mount for my NUVI traffic GPS.

some aluminum i had laying around, a hacked up garmin car dash top mount, cig lighter socket, paint and some bolts.

valve lash check time.

procedure is just like on an S14, just fewer valves and different special tools.  unfortunately all the exhaust valves were way too tight.  ordered a bunch of shims, put it back together and went for a ride.

  valve bucket tools from Ken (Kenneth Lively [])  work great!  the one on the left rotates to depress the valve bucket, the one on the right holds the bucket down so you can R&R the shims. 

took it apart.  dang that is easy.

a bit dirty in there

evidence of cracked crankcase breather hose mess.

these are going to RC Engineering for cleaning

some quality time spend in the laundry room sink.

original project goal is to replace all fuel and cooling hoses, and replace the brake soft lines.

more progress today.
TB going back together.  replaced all the hoses.  did initial setting of the TPS

 added the little switch for the choke light.  not much room for it..

cut all the wire ties, wiped down all the wires, took apart and cleaned all the connections.

then drained coolant and removed all the coolant hoses.  or tried to.  looks like i will have to cut the one that goes through the crankcase cover to get it out.  will new one slide in?  waiting on the new ones to arrive.

changed the original clutch cable (30k miles).  old one didn't seem bad, i just had a new one available.  wow!  new one is so much smoother!

then replaced all the coolant hoses (they too were original).  the combo of dish soap and lengthwise folding made getting the crank cover hose in easy!

then reassembled the throttle bodies and installed.

front brake line replacement and some wiring tomorrow.  injectors due back from RCEngineering this week.

front brake lines replaced with Spiegler braided.

finished cleaning and straightening up the wiring.  choke light works!

airbox and AFM reinstalled

"while i was in there" ran unswitched power and ground from battery to fairing to drive light relays.

the pile of 1993 dated hoses...

now that front of bike is done, time to take apart the drive line and pull tranny for spline lube.
ok, back of bike came apart today.  need to lube the splines on both ends of the drive shaft and the tranny input shaft.

rear brake system off

diff off

yep, driveshaft splines need some help

then up on the lift so that the center stand can come off for the tranny pull

tranny before, clutch splines were DRY.

tranny after

clutch looks ok.

shop with pieces everywhere

tranny and driveshaft back together


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