1981 GSX1100 Katana Based Project

[Shin-Ken 1074]

TNK fork spring set.

TNK springs 1 by Max Mutarn, on Flickr




OEM fork spring.
SZ OEM fork spring by Max Mutarn, on Flickr


TNK fork spring.
TNK springs 2 by Max Mutarn, on Flickr



OEM v TNK spring set.
OEM v TNK by Max Mutarn, on Flickr

[Shin-Ken 1074]

Have a sniff of it. I wouldn't be at all surprised if it's the original fork oil from the factory, and they were fond of fish oil back then.
Stinks to high heaven after a few years.

No fish oil today Grimly. These are re-manufactured Suzuki forks by a company in Japan so the original oil is long gone, thankfully. A nice feature is they remove the OEM anti-dive top module and replace it with a reliable manual adjustable damper unit. No need for anti-dive hoses and brackets, much lighter now.

Damper adjust by Max Mutarn, on Flickr


The sludge is the usual result of not changing the fork oil at 10,000km. I have seen worse looking oil from forks from the many sets I have worked on so not a surprise really.

[Shin-Ken 1074]

Fork internals are in good shape, the wave washers have almost no wear and the friction bushes are almost mint as expected. When PMC (Performance Motorcycle Creative) in Japan re-manufacture these forks they replace all the internal parts including friction bushes so the forks leave their workshop as "New" forks. The forks were painted black and the "KYB" decals had been applied when I bought them, not original finish for a 1981 SZ but this build is not a restoration to original spec so no drama leaving them as is. In fact I think the black finish will go well with the build as only the battery cradle is in aluminium finish with everything else being silver or black.

My guess is this is the first time the forks have been worked on since they were re-manufactured which is why all the internal parts are minty, just tired fork oil that has been there for to long. A clean up and install the new consumables and they will be ready to go.

Fork assembly 1 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Fork parts cleaned and good to go.


fork internals cleaned by Max Mutarn, on Flickr


Having a 19mm hex drive tee handle makes life easy when working on the forks.

Damper rod tee by Max Mutarn, on Flickr

[Shin-Ken 1074]

New fork seal time. Shaped a bit of round bar to make a seal remover tool. Unlike the tradition way to remove a seal with a screwdriver, this way no slipping or risk of damaging the seal housing.

Fork seal remover 1 by Max Mutarn, on Flickr


Fork seal remover 2 by Max Mutarn, on Flickr


Fork seal 3 by Max Mutarn, on Flickr


Fork seal 4 by Max Mutarn, on Flickr

[Shin-Ken 1074]

My socket set are thick walled and will crush the raised rib section of the fork seal if I used them to install the new seal. Lucky for me I don't throw out steel or pipe off cuts and just pile them up in a drum waiting for a job. Ratting through the drum I found a pipe that is a perfect fit for the new fork seal, clears the seal rib and just fits inside the fork leg. Made a cedar strike plate for the top of the pipe and taped it in place with the ever reliable silver duct tape.

Fork seal drift 1 by Max Mutarn, on Flickr


Fork seal drift 2 by Max Mutarn, on Flickr


Fork seal drift 4 by Max Mutarn, on Flickr


Fork seal drift 5 by Max Mutarn, on Flickr




Fork seal drift 6 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Change of plan, the aluminium preload unit threads wont engage the fork threads. Can't see any damage to the threads on the aftermarket preload. The OEM preload unit spins on without any problem so for now the OEM preload will be used and I'll sort out the problem another day, at least that can be done with the forks fitted.

The problem preload.

aftermarket preload by Max Mutarn, on Flickr

[Grimly]

I came across that fork preload thread problem - two sets of forks from Zuk, both the same diameter, different threads. That's why I ended up using the air caps but cut them down and turned them into mechanical pre-loaders.

[Shin-Ken 1074]

I came across that fork preload thread problem - two sets of forks from Zuk, both the same diameter, different threads. That's why I ended up using the air caps but cut them down and turned them into mechanical pre-loaders.

Hi Grimly, good work around on your pre-load thread problem.

[Shin-Ken 1074]

The OEM steel fork brace that sits inside the front guard is a not so light 780 gram part. Replacing it with a Daytona aluminium fork brace however, the Daytona is old and the plastic fork dust seal retainer is brittle and flimsy, not good. Had an aluminium retainer made to replace the plastic item and it should
do the job for many years to come.


OEM steel fork brace.
OEM fork brace by Max Mutarn, on Flickr

Plastic retainer.
Plastic retainer by Max Mutarn, on Flickr


Aluminium retainer
Aluminium retainer by Max Mutarn, on Flickr

[Shin-Ken 1074]

Daytona ally fork brace with ally retainers.

Daytona ally brace by Max Mutarn, on Flickr

[Shin-Ken 1074]

Numbers time for the fork parts being swapped or deleted, not the total fork weight right now.


OEM anti dive units and hoses.
OEM antidive by Max Mutarn, on Flickr


OEM anti dive hose brackets.
OEM anti hose bracket by Max Mutarn, on Flickr

OEM fork brace, anti-dive units,anti-dive hose brackets and fork springs total = 2,546 grams.

[Shin-Ken 1074]

Swapped anti-dive units from OEM to PMC units.


DW antidive by Max Mutarn, on Flickr

OEM 1 x brace, 2 x springs, 2 x anti-dive and hoses and 2 x anti-dive hose brackets = 2,546 grams.


1 x Daytona fork brace, 2 x PMC anti-dive units and 2 x TNK fork springs total = 1,312 grams.


Total weight removed from fork set = 1,234 grams.

This is where having to use the OEM preload units hurt, they are double the weight of the aftermarket preload units.

[Shin-Ken 1074]

DW 180 complete fork including oil = 4,300 grams each. Fork brace not included.


DW fork by Max Mutarn, on Flickr

[Blower]

Yes, chipping away at many of the smaller and seemingly insignificant parts is a big help in reducing weight as each part contributes to the end goal. While the big ticket items like pipes, wheels, battery, seat, clip-on bars and weights, brake rotors, sprockets, chain, chain guard, center-stand and side-stand are the go-to parts of the reduction plan, there is a lot of weight savings to be had by including as many of those smaller parts as possible even down to bolts and washers.

When these bikes were designed and built weight was not at the top of the check list so parts like pivot bolts and bearing spacers were made the way they had always been made - with solid steel, tough, reliable and heavy! Thankfully a hollow pivot bolt and an aluminium bearing spacer will do the same job at less than half the weight.

Yeah, the OEM bearing spacer is pretty sad. It came with the donor swing arm and thankfully all I needed was the swing arm.

OEM steel pivot and bearing spacer by Max Mutarn, on Flickr


Hollow pivot and ally spacer by Max Mutarn, on Flickr


The best weight saving is when parts can be deleted completely rather than modified or swapped. A couple of kg have been saved by deleting parts completely:

Anti-dive unit top section, hoses and brackets
Front brake hose manifold
Front wheel speedo dust cover
Front guard speedo cable rubber guide
Wire speedo cable guide on fork lower
Fork OEM steel brace
Centre-stand
Tool roll bracket
Number plate bracket
Rear guard sub-frame
Rear foot pegs
Air box and filter
AUX 12 volt switches
Helmet lock and bolts
Lift handle and bolts
Seat strap




The goal is 180 kg from a starting point of 232 kg and at this stage it is in the low 180's however, I don't think those last few kg are going to be easy to find. I like your confidence and I hope you are right.

Are you sure the aluminum spacer tube won't collapse when you tighten the pivot bolt to torque?