1981 GSX1100 Katana Based Project

[Rob S.]

Yeah, just reread your first post.

[Shin-Ken 1074]

Have double checked the running tally in the build book and there are some parts that I listed twice, the front guard and bolts and headlight frame which has put the dry weight in error, oops. I have checked and corrected the running tally and then cross checked it with the wet weight.

So the build at the end of stage 1 has the following weights confirmed by commercial scales.

Dry weight = 181.603 kg.

Wet weight = 206.00 kg.

Total weight reduction for stage 1 comparing the factory dry weight vs the DW build dry weight = 50.397 kg.

Total weight reduction for stage 1 comparing the factory wet weight vs the DW build wet weight = 54 kg.

How can there be two different numbers in weight saving? I suspect the factory manual figures are not accurate but which one is the question? The DW build figures are correct as the commercial scales used to weigh the DW have been calibrated and are weighing accurately.

So what does it mean now? Best case is the DW is 54 kg lighter and worst case is the DW is 50.397 kg lighter. I have no control over how the factory manual was put together but I did have control over how the DW was put together and I am very happy with the end result no matter what the manual states.

Motorcycle design and materials have advanced a great deal (not always for the better) over the last 43 years since the 1981 GSX1100S Katana was made by Suzuki. However, it is interesting to see how the DW build compares with one Suzuki's latest bikes, the 2024 GSX-S1000. Suzuki Australia currently list the 2024 GSX-S1000 wet weight at 214 kg. Compared to the wet weight of 206 kg for the DW, looking at those numbers I'd have to say the project has been a success.

Four aluminium bolts arrived yesterday, watch this space.

Aluminium allen bolts by Max Mutarn, on Flickr


Dry weight running tally = 181,603 grams.

[Shin-Ken 1074]

Have swapped the rear tank mount titanium bolts for aluminium bolts today, the ally bolts are much lighter.

Ti tank bolts
Tank bolts Ti by Max Mutarn, on Flickr


Ally tank bolts
Tank bolts ally by Max Mutarn, on Flickr

Dry weight running tally = 181,595 grams.


I have found 9 other titanium bolts that could be replaced with aluminium bolts. My supplier is out of stock right now for M6 x 15 ally bolts so it could be a month before the bolts are swapped.

[Shin-Ken 1074]

The test rides to check on things have been going well so far however, one issue has surfaced that I was hoping wouldn't. I installed an engine oil temp gauge to monitor temps during the test rides and the oil is hitting 122.5 C on 29 C days with 80% humidity. To cope with Summer here the engine will need an oil cooler, adding weight is not what I wanted to do but frying an engine is even worse than adding weight so time to start making brackets and lines for the cooler. Looks like this thread still has a bit of life in it.

[steve murdoch]

Were you stuck in traffic or maybe having a lot of fun in the upper rev range?
That seems like a very high engine temperature for just a 29C day. I'm sure you get hotter days than that.
Just wondering if your temp gauge is properly calibrated?

[Shin-Ken 1074]

Were you stuck in traffic or maybe having a lot of fun in the upper rev range?
That seems like a very high engine temperature for just a 29C day. I'm sure you get hotter days than that.
Just wondering if your temp gauge is properly calibrated?

Hi Steve, flowing city traffic and open road 100kph. I'll check the gauge with my "Old School" thermo and see if it is reading correctly. The other option is the engine has had some work and could be a bit sportier than a stock 1135 EF engine. Didn't remove the head so no idea what capacity it is. Could explain why it launches instantly with the slightest touch of the throttle, almost like fly by wire!

Yes, Summer here is 40C plus with 95% humidity and when it's that humid air cooling is not as effective as at lower humidity levels.

[Rob S.]

...could be a bit sportier than a stock 1135 EF engine.

In any case, the stock 1135 came with an oil cooler, so...

Also, if you're only going 100 kph, you're not riding correctly. It's supposed to go 100 mph (160 kph).

[pdqford]

Having not read this entire thread, but any chance the stator is Adding heat to the oil?

[Shin-Ken 1074]

Having not read this entire thread, but any chance the stator is Adding heat to the oil?

It could add some heat but not enough to spike the heat to over 130C. The reason for not fitting a cooler was to save weight. With no cooler an oil temp gauge was installed to monitor the oil temp however, even in mild weather conditions the oil is getting too hot. On a (brisk) test ride yesterday the oil temp got 132 C so it needs an oil cooler, as they were fitted originally by Suzuki. That is what testing is for, to evaluate and confirm and this test confirms a cooler is needed.

[Lorenzo]

It could add some heat but not enough to spike the heat to over 130C. oil temp gauge was installed to monitor the oil temp however, even in mild weather conditions the oil is getting too hot. On a (brisk) test ride yesterday the oil temp got 132 C so it needs an oil cooler, as they were fitted originally by Suzuki. That is what testing is for, to evaluate and confirm and this test confirms a cooler is needed.

Those pared fins. Not much but they would've helped...

[Shin-Ken 1074]

Those pared fins. Not much but they would've helped...

True, but they had to go and not just to loose weight, the sump fins had to go to fit the titanium pipes. I could always fit a stock sump with fins to see if it makes a difference, yeah,nar.

[Lorenzo]

No need for down-under side of pipes to be round.

[Rich82GS750TZ]

He’s in Australia. His whole bike is “down-under”.

Sorry. Someone had to say it.

[Lorenzo]

[no pun intended obviously]

[Shin-Ken 1074]

He’s in Australia. His whole bike is “down-under”.

Sorry. Someone had to say it.

Glad someone did.