1981 GSX1100 Katana Based Project

[Shin-Ken 1074]

Yesterday was also the first ride with the modified fork pre-load units installed and they worked very well. The 29 mm spacers were used and the front tyre pressure in the Bridgestone T32 Radial was 34 PSI with 40 PSI for the rear. Going for a ride tomorrow and will drop the pressure to 33 front and 39 rear to see if it improves handling.

The recommended tyre pressure is 36 PSI front and 42 PSI rear however, those pressures are for a stock scooter and my scooter is 62 kg lighter than stock so there is some fine tuning to be done with the tyre pressures before I find the Goldilocks pressure.

Running Tally = 197.933 kg.

[Shin-Ken 1074]

The 1197 cc pistons have now been installed in the newly bored barrels and the head with its new valve seats, valves, valve guides, valve stem seals, spark plugs and cam followers have been bolted together. New base and head gaskets to complete the engine refurbishment now done. Yesterday saw the first 200 km of the ring break-in done with another 100km to go before the first oil and filter change, sump and oil pick-up inspection. Will also be splitting the oil filter element open to inspect the pleats.

During the 200 km ride yesterday the oil temp didn't go above 96.7 C so engine heat management using the small volume oil cooler is doing well so far.

[Shin-Ken 1074]

The fork caps have had a tidy up and now have a set of pre-load spacers to replace the OEM adjustable units that were like dragging a boat anchor around. For an improved range of pre-load settings the spacers are: 29mm, 36mm, 42mm and 48mm.


Fork caps GS1000 1 by Max Mutarn, on Flickr


Fork pre load spacer set 1 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The GS1000 fork caps have been machined and now fit the Kat forks and are a few grams lighter, bonus!


Running Tally: 197.933 kg.


Fork caps 1 by Max Mutarn, on Flickr


Fork caps 2 by Max Mutarn, on Flickr


Fork caps 3 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The ignition cover is pretty light at 1.89 mm thick and when it is painted and the Suzi emblem plate is attached the grinding will be out of sight thankfully. From 245 grams down to 123 grams is a good result and one of those mods that will never be seen. Had to add 10 grams to the 235 gram pic as the Suzi emblem plate was not attached to the cover in the photo on the scales.


Ignition case 5 by Max Mutarn, on Flickr


Ignition case 6 by Max Mutarn, on Flickr


Ignition case 7 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Going to swap the OEM Kat fork pre-load units for modified GS1000 fork caps. The GS 1000 caps need to have some machining done to fit the Kat forks however, that is good news, they will be lighter by a few grams. After the caps have been trimmed I'll have the final weights for both units.

OEM Kat fork preload unit.
Preload OEM Kat 1 by Max Mutarn, on Flickr


Modified GS1000 fork cap.
Modified GS Preload 1 by Max Mutarn, on Preload 1 by Max Mutarn, on Flickr


Fork caps by Max Mutarn, on Flickr

[Shin-Ken 1074]

Trimming the cover to 0.5 mm thick along the inner edge. The outer case is now 1.89 mm thick.

Ignition Cover 4 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Some more Dremel work done today thinning the ignition cover, still have more material to remove before the case is about 2mm thick. I need to order some aluminium allen bolts for the ignition cover to help get the overall weight down.


Ignition case 1 by Max Mutarn, on Flickr


Ignition Case 2 by Max Mutarn, on Flickr


Ignition Case 3 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The internal gussets have been removed and now the case walls need to be thinned down, they only need to be thick enough to keep water out.


Ign Case Stock by Max Mutarn, on Flickr


Ign Case Mod 1 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Found the Dremel and have started to hog out the ignition cover, would like to get it down to 100 grams.


Ign cover d1 by Max Mutarn, on Flickr


Ign cover d2 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Started working on the ignition cover to make it lighter, now I just need to find where I left the Dremel.

DW Ign cover1 by Max Mutarn, on Flickr


DW ign cover2 by Max Mutarn, on Flickr


DW ign cover3 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The aftermarket fork pre-load units and the ignition cover arrived today so this weekend should see some changes. The pre-load units were advertised as being for the 81 GSX1100S however, the threads look a bit course when checking with the MKI eyeball so that will need to be checked.

The ignition cover is going on a diet which is why I bought a damaged cover to experiment with. The plan is to shave the case thickness in places and remove the centre of the case where the "Suzuki" emblem plate sits. I think 80 -90 grams can be removed from the case, should know soon.


The OEM Suzuki preload units weigh 118 grams each compared to the 74 grams each for the aftermarket units, a 78 gram reduction for the two units.

Fork preload1 by Max Mutarn, on Flickr Mutarn, on FlickrIgn case 1 by Max Mutarn, on Flickr


Ign case2 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The aftermarket aluminium fork pre-load units to replace the heavy OEM pre-load units and ignition cover are on the way from Japan this week. Hoping to have them by Friday and work on the cover over the weekend.

[Shin-Ken 1074]

While the pipes are off it will make it easy to clean them and be ready for installing once the engine is back together. Used the Bug/Tar Gel on a cloth then washed the pipes in hot water with dish washing detergent. They don't look like new but they do look pretty good considering the miles on them.


Tipipes1 by Max Mutarn, on Flickr


Tipipes2 by Max Mutarn, on Flickr


Tipipes3 by Max Mutarn, on Flickr


Tipipes4 by Max Mutarn, on Flickr

[Shin-Ken 1074]

With the front collector springs removed there is no need to keep the rear springs, one in all in or one out all out. This has been a good week removing weight from the build, another 1,038 grams lighter.


Running Tally = 198.165 kg

Muffler springs1 by Max Mutarn, on Flickr