1981 GSX1100 Katana Based Project

[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.

[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]

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.]

Running tally = 182,956 grams.

With you on?

[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.

[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.

[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]

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

[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]

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.

[steve murdoch]

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

[Shin-Ken 1074]

I wasn't happy with the 6mm allen bolt holding the new front brake res, it just didn't look right, and if it doesn't look right it isn't right. Swapped it for a 5mm allen bolt, much better and as a bonus it is almost half the weight of the 6mm.

Front res M6 by Max Mutarn, on Flickr


Front res M5 by Max Mutarn, on Flickr


Running tally = 183,059 grams.

[Shin-Ken 1074]

The res swap is done and dusted. The Brembo res including the DIY bracket, hose, clips, bolts, washers and brake fluid came in at 77% lighter than the Nissin res assembly, 152 g is a pretty good weight saving for a small part like the front res.

The Nissin res = 198 g.

Brembo res = 46 g.

Front res 1 by Max Mutarn, on Flickr


Front res 2 by Max Mutarn, on Flickr




Running tally = 183,062 grams.

[Shin-Ken 1074]

One of the jobs I'd like to start this weekend is swapping the OEM Nissin front brake res for a lighter Brembo res. The Brembo res is not supplied with a bracket but that isn't an issue as it allows me to make a bracket and I have a cunning plan for the bracket.


Nissin Res by Max Mutarn, on Flickr

[Shin-Ken 1074]

Since fitting the GSX 1135 EF OEM oil cooler I have been monitoring the oil temp using a digital gauge and so far so good. The 1135 EF OEM front guard has a deflector fitted as stock however, the 1981 SZ Katana 1100 front guard does not have a deflector so I have been curious to know about the air flowing around the Kat guard to the oil cooler as the oil cooler is behind the guard and not positioned higher up in the air stream. Using a fan and thin paper strips for streamers I have cobbled together a very, very basic air flow rig to see what is happening.

Interesting result with the streamers, the boundary layer on the guard has the air hugging the guard and almost no air flow leaving the guard surface and going to the cooler as the flat streamers show.

The DIY deflector in the cowl is working well to direct air to the cooler and the Daytona fork brace which has a two deflectors in its design, is also working well to direct air into the cooler as the streamers show in this very crude test.

Oil cooler 81 by Max Mutarn, on Flickr


Oil cooler 82 by Max Mutarn, on Flickr