1981 GSX1100 Katana Based Project

[Shin-Ken 1074]

The 02 sensor reading shows that at WOT things could be improved a fraction by going up a size in main jets so today was swapping main jets day. Removing and installing the carbs is so quick and easy on this build because it isn't fitted with an airbox, with the tank off and throttle cable released, it is just the four inlet boot clamps to release and slid the carbs out. Larger jets are now installed and ready for testing with the 02 sensor tomorrow.

I reshaped a screwdriver to match the Mikuni jet slot, doing this eliminates damage to the jet shoulders that a standard screwdriver causes due to the screwdriver taper putting pressure on the jet top edge and none on the lower section of the jet slot.
Carb 20 by Max Mutarn, on Flickr


Carb 30 by Max Mutarn, on Flickr


Carb 31 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The oil cooler lower brackets after drilling and now primed, a few grams lighter.

Oil cooler 31 by Max Mutarn, on Flickr

[Shin-Ken 1074]

A mate has been helping me (he knows what to do and I get to swing the spanners) sort out the carbs using his 02 kit, very helpful! After working our way through a few main jet sizes and needle clip positions we are very close to dialing in the carbs. 02 readings for idle 1/8, 1/4, 1/2, and 3/4 throttle position are done and dusted with only WOT needing a fraction more fuel to be happy. Will be fitting the next size up main jets and test riding on Monday if the weather is fine. When we started dialing in the carbs the DW Kat had plenty of get up and go with a crisp throttle response delivering instant power compared to my stock Kat however, this is a different animal. The 36 mm carbs, no airbox, 60 mm I.D. 4 - 1 exhaust system and Yoshi cams bolted to the 1135 EF engine is nothing like a stock Kat. At first I was very happy with the DW set up as I have been riding my stock Kat for the last 38 years and this was my benchmark. But now after some tinkering with the carbs using the 02 kit the improvements to performance are amazing and at this stage there really isn't a need to go any further as WOT riding is pretty much never going to happen when it pulls 100 kph (60 mph) using less than 1/8 throttle however, when you are so close to having a ride well sorted why not go all in!

The 02 kit is only a temporary install while we work on the carbs so the 02 sensor and exhaust pipe sleeve are a slip fit and sealed with aluminium tape to prevent false readings.
02 Kit 1 by Max Mutarn, on Flickr


02 gauge.
02 dial by Max Mutarn, on Flickr

[Shin-Ken 1074]

After the fail with the first cooler it's oil cooler MK II time. Decided to not use the MK I cooler lower bracket, too heavy. The MK II lower brackets are individual brackets and much lighter as the scale shows when compared to the MK I bracket, 58 grams vs 18 grams = 69% weight reduction for the lower bracket. Today was spent sorting out the optimal oil cooler position and making the lower brackets to suit, minimal filing needed this time.

Although I am not happy having to add an oil cooler to the build, I have kept the weight to a tolerable level. So far the cooler, lower brackets and engine oil cooler fittings weigh a total of 355 grams.

Cooler top brackets, hoses and clamps are next on the list and maybe a protector screen for the oil cooler?

Oil cooler 27 by Max Mutarn, on Flickr


Oil cooler 28 by Max Mutarn, on Flickr


Oil cooler lower brackets before they are drilled out to lighten them.
Oil cooler 29 by Max Mutarn, on Flickr


Engine oil cooler fittings.
Oil cooler 30 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Waiting a few days for the new paint on the cooler to cure.


Oil cooler 25 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Hi Rob, Wow, your Kat looks the goods! Wheels, EFFY head - great mod, front and rear end, is that an RF 900 swingarm? Fantastic work on the Kat and thanks for the pics, you can post them anytime when you have Kat-porn like that.

Cheers.

[Aussie Rob]

Max, Fully understand the weight thing, I admire your commitment trimming the Kat down.
You are correct about the OEM carbs, I loved them when the bike was standard but they don't cut the mustard now. A set of Mukini 36mm now sit in their place.
I did go for a sporty Kat and after a 9 year rebuild I am very happy with the way she turned out .
Hope you don't mind me dropping some pics.

Katana rebuild by RobK67, on Flickr

Katana rebuild by RobK67, on Flickr

[Shin-Ken 1074]

Max, I fitted a TRUB7B oil cooler when I added an oil cooler to my Kat. Size is 70 x 280 x 38mm (2.75 X 11 X 1.5 in) and weighs just under 500gms (1lb). Fits in nicely between the side cowlings. I modified the in/outlets to fit 1/2" NPT fittings.
Works a charm.
Pics always help. I have more if needed.

Nice bike by the way, you have done an amazing job.

DSCN1093 by RobK67, on Flickr
IMG_4458 by RobK67, on Flickr

Hi Rob, thanks for your tip on the TRUB7B cooler, a tidy looking unit that fits the Kat well and looks good with those USD forks! On any other build I would chase up the TRUB cooler however, this build is focused on weight reduction so light parts are the name of the game this time. I have bought a Davies Craig "Hydra-Cool" oil cooler, made in Australia and pressure tested with a 2 year warranty.

Fits the Kat and most importantly is very light at only 317 grams. The other feature on this cooler is the barb connection, using 9.5 mm hose and clamps is much lighter than braided lines with AN or NTP fittings and also eliminates 90 degree angles from the plumbing. Same goes for the plumbing from the block, barbed aluminium is light. Braided lines and AN or NTP fittings are a great product however, not for this build. Once the paint has cured on the cooler, painting the outer edges black and leaving the cores/fins silver (picked up the cooler two hours ago) I'll weigh the complete system, my guess is cooler, connections, hoses/clamps and brackets will be less than 600 grams.

Interesting, going by the decal and the signature block your Kat is a 1000 model, is it still running OEM slide carbs or have your replaced them with modern go fast carbs, the top end oil system and USD forks hint towards this being a very sporty Kat? Keen to see other pics of your Kat when you get the chance to post.

Cheers mate.

Oil cooler 22 by Max Mutarn, on Flickr


Oil cooler 23 by Max Mutarn, on Flickr

[bonanzadave]

Those braided lines look much nicer than the rubber hoses and hose clamps.

[Aussie Rob]

Max, I fitted a TRUB7B oil cooler when I added an oil cooler to my Kat. Size is 70 x 280 x 38mm (2.75 X 11 X 1.5 in) and weighs just under 500gms (1lb). Fits in nicely between the side cowlings. I modified the in/outlets to fit 1/2" NPT fittings.
Works a charm.
Pics always help. I have more if needed.

Nice bike by the way, you have done an amazing job.

DSCN1093 by RobK67, on Flickr
IMG_4458 by RobK67, on Flickr

[Rob S.]

Suggestion: don't toss the bad cooler back in the pile. That's something I would do!

[Shin-Ken 1074]

I guess the silver lining is that it happened on a short, low speed test ride.
Obviously that could have been ugly.

My rule is whenever working with coolant or oil always do the first test at low speed and around the block a few times to check everything. If there is a problem and it can't be ridden, pushing the bike back home is no drama compared to what may happen if you just get out there and fang it from the get go and it all goes pear shaped at high speed, like oil on the rear tyre if I had kept riding with the leak.

[steve murdoch]

I guess the silver lining is that it happened on a short, low speed test ride.
Obviously that could have been ugly.

[Shin-Ken 1074]

Cooler and hardware have been removed, pipes and block have been cleaned and non-cooler hardware installed. So it's Plan B and another cooler, the bad news is the next cooler will be heavier than the first cooler. The good news is the DW is 864 grams lighter without the cooler right now.


Running tally = 181,595 grams.

[Shin-Ken 1074]

You are correct about the weight Diirk, bit of a downer. The cooler bracket looks O.K. just a pity the cooler itself is not as good looking right now. Just went for a test ride to the end of the street and number 1 header looked like there was a BBQ going on down there, a nice smoked brisket BBQ! The cooler has a split in the lower plate so no joy there. Will sort through the other coolers and find one that keeps the oil on the inside.


Oil cooler 19 by Max Mutarn, on Flickr


Oil cooler 18 by Max Mutarn, on Flickr