1981 GSX1100 Katana Based Project

[steve murdoch]

Comparing the photos you are right.
Obviously a small thing but your eye would have been drawn to it.

[Shin-Ken 1074]

Comparing the photos you are right.
Obviously a small thing but your eye would have been drawn to it.

Yes, as soon as I bolted it on I knew it had to be swapped for a 5mm.

[Shin-Ken 1074]

The light weight Brembo res is supported by a bracket I made from 2.5mm stainless steel rod, strong enough to do the job and not look too industrial, keep it tidy and very light! I made the top of the bracket with a slot to allow for adjustment and some wiggle room if needed when positioning the res. The Kat is on the sidestand, hence brake fluid level in the pic.

Front res 3 by Max Mutarn, on Flickr

[Shin-Ken 1074]

A friend came up an interesting suggestion for the electrics that would delete the GSX1150EF igniter, saving weight and one less electric component to worry about. His idea was to install a Dyna S pick up set and after this is installed the igniter can be removed. Sounds like a win!

With the GSX1150 EF engine installed in my Kat frame I had made an aluminium bracket to fit the EF igniter to the Kat however, if the Dyna S pick ups are used the bracket and igniter can be deleted, now its a win,win!

Has someone here done this mod to their GS and were you happy with the mod?

Dyna Sjpg by Max Mutarn, on Flickr


EF igniterjpg by Max Mutarn, on Flickr


Igniter bracket by Max Mutarn, on Flickr

[Aussie Rob]

Max, fitted the Dynamic S to my Kat. It’s a piece of cake to fit and set up timing.Very happy with it.
Cheers, Rob.

[Shin-Ken 1074]

Max, fitted the Dynamic S to my Kat. It’s a piece of cake to fit and set up timing.Very happy with it.
Cheers, Rob.

Thanks Rob, good to hear it works as advertised.

Cheers mate.

[Shin-Ken 1074]

There may not be any big ticket items left to modify or delete to save weight however, there is always something that can be worked on. This week it is the seat pad.

This is the first version for the seat pad and although light it could be lighter.

Seatpad1 by Max Mutarn, on Flickr


The second version, 103 grams lighter.

Seatpad2 by Max Mutarn, on Flickr


The lighter seat pad installed.

Seatpad3jpg by Max Mutarn, on Flickr


Seatpad4 by Max Mutarn, on Flickr


Running tally = 182,956 grams.

[Rob S.]

Running tally = 182,956 grams.

With you on?

[Shin-Ken 1074]

With you on?

Not yet!

The running tally numbers are for dry weight which is fine however, there is no fun with no fuel!

After test rides to check fuel consumption it works out that 13 litres of fuel gives a range of 219.375 km. Using those numbers I can reduce the fuel load from a full tank of 21 litres down to 13 litres and still have enough fuel to have fun for a few hours.

So why do these fuel numbers matter for the project? Less fuel is less weight as well as lowering the centre of gravity and both of those are a good thing to make for fun riding.

The take away from the reduced fuel load is knowing how much fuel I need for a total riding (curb) weight for the Kat and not carry extra fuel that isn't needed.

So as of today the riding total weight of the Kat (without me aboard) is:

199.864 kg

Riding a sub 200 kg 1981 Katana fitted with an EF 1135 engine has transformed my riding experience to a level of enjoyment I didn't fully understand could be possible at the start of this project! The result so far is beyond all my expectations and although this has been a long, expensive and at times a very trying build to find solutions to reducing the weight I can say, hand on heart it has been worth the effort, no doubt what so ever!

I believe there are still some areas that can be modified to reduce the weight further so there will be updates in the future. I am still thinking about installing the Mikuni 38mm flat slide carbs but that is a job for another day.

[Rob S.]

No one has offered an opinion on this, but this may be right up your alley. My '82 11E doesn't have a center stand, so that's good for weight savings. But, if it did have one might not the center of gravity be lower?

Not a huge difference either way, but as someone who's weighing every tenth of a gram, I thought you might have an opinion. I think it's better off without the center stand, as the lowering of C. of G. with it, if any, would be imperceptible.

[Shin-Ken 1074]

No one has offered an opinion on this, but this may be right up your alley. My '82 11E doesn't have a center stand, so that's good for weight savings. But, if it did have one might not the center of gravity be lower?

Not a huge difference either way, but as someone who's weighing every tenth of a gram, I thought you might have an opinion. I think it's better off without the center stand, as the lowering of C. of G. with it, if any, would be imperceptible.

I don't know the weight of an 11E centre stand but a Kat centre stand with bolts, bushes and spring is 2,330 grams so the centre stand is long gone from the build. The centre stand is the lowest bit of hardware (not including wheels) so its effect on the C of G would be minimal compared to having that weight up around the bars, clocks and fuel. Someone here may have the correct answer to the stands effect on C of G but it isn't me.

[Shin-Ken 1074]

Took the Kat out today to test the modified (lighter) seat pad for a two hour ride and so far so good. The new seat pad is smaller in area and 26mm thinner and has lowered the riding position. Although the seat pad is thinner the ride was very comfortable and in fact is more comfortable compared to the previous seat pad with the higher sitting position. I didn't think lowering the sitting position by 26 mm would make such a difference to improving comfort as well as improving handling with the change to the riding position. In this case changing the ride to suit the rider has turned out well even if the reason for the change was to reduce weight with no consideration for improved comfort and handling.

[Shin-Ken 1074]

Now that the Project is a going concern and is performing well, there is now time for some tweeking to shed some grams here and there when any excess weight is identified. There is no bar buzz being generated throughout the rev range so the bar end-weights can go as well as cutting 20mm off the clip-ons to lighten the bars. My guess is around 140-160 grams will bite the dust, will know the answer this weekend after surgery.

[Shin-Ken 1074]

Have removed the bar weights and cut 20 mm off the end of each clip-on.

Barweights 20mm off cut by Max Mutarn, on Flickr


Running tally = 199.724 kg

[Shin-Ken 1074]

Next thing to go on a diet will be the mirrors. Right now the Kat is fitted with genuine Suzi mirrors and being genuine they are a quality part however, that quality includes weight. I found a set of used Barrac mirrors with aluminium stems, compared to the OEM steel stem these should be lighter than what I have now, fingers crossed. Barrac also make these in carbon, lighter but expensive!

The mirrors should arrive in a few weeks with the rest of my parts order.

Barrac Mirrors 1 by Max Mutarn, on Flickr