1981 GSX1100 Katana Based Project

[Shin-Ken 1074]

Took the Kat over to my mates place on the weekend to finish the wiring and some final checks on the carbs before starting the fine tuning with the 02 sensor. Tuning to be done later this week.

Carbs 01 by Max Mutarn, on Flickr


Wiring 1 by Max Mutarn, on Flickr

[Shin-Ken 1074]

The replacement main jets arrived today and they have been installed. Carbs on, carbs off, carbs on, carbs off. Thankfully the build is not using the OEM airbox so its an easy job to remove carbs.

New Jet by Max Mutarn, on Flickr

Carbs have been re-installed, again, ready for the tune up this weekend. Fingers crossed!

[Rob S.]

Perfect! My kind of muffler.

[Shin-Ken 1074]

That looks like a nice, reasonably sized muffler. Hope you haven't got it jammed with heavy baffles and fiberglass.

Nope, doesn't appear to be jammed up.

Can by Max Mutarn, on Flickr

[Rob S.]

That looks like a nice, reasonably sized muffler. Hope you haven't got it jammed with heavy baffles and fiberglass.

[Shin-Ken 1074]

02 sensor is the way to go. I've been tuning automotive carbs for decades. Finally bought an 02 setup and I can set dual carbs up in a matter of hours rather than a few days of trial and error.

Yep, dialing in the fuel/air ratio using an O2 sensor is accurate and saves so much time, no crystal ball or star gazing involved to get it right. I like uncomplicated old school bikes without high tech systems and management programs however, I am all in when it comes to using this tech to get the numbers sorted.

[Shin-Ken 1074]

The plan is this weekend to finish up the wiring and then dial in the carbs. An engine builder I know well has advised me on initial main jet size to begin setting up the carbs. New jets should arrive this Friday. The engine has a few variables to contend with compared to a stock engine, it isn't a Hotrod but there are a few changes:

GSX1135 EF engine fitted with Yoshi profile hollow camshafts with a different lift to the stock EF camshafts, 750 F 36mm carbs with short velocity stacks - no airbox and a 4-1 exhaust system with a 58 mm I.D. pipe from the collector to the muffler outlet to help it breath!

To help dial in the carbs we are going to use an O2 sensor mounted in the pipe just forward of the muffler. A local muffler shop has welded a sensor bung into a sleeve they made to fit my titanium pipes, great work and did it on the spot in 15 minutes.

The sleeve with the O2 sensor bung is only fitted to the pipe when setting up the carbs and then removed once the carbs are sorted. Several of my friends have exhaust systems with the sensor bung welded in to the pipes and leave the bung in place however, I don't want to have the extra weight of the sleeve and sensor bung hanging off the system so it will be removed until needed for the next tune-up.

If all goes well I should have good news after the weekend.

O2 a by Max Mutarn, on Flickr


O2 b by Max Mutarn, on Flickr


O2 c by Max Mutarn, on Flickr


Ex 2 by Max Mutarn, on Flickr


Ex 1 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Yeah, I agree 100% with you about the older GS rear brakes being over engineered. Light weight modern brake systems prove just how light the brake components can be compared to the older parts.

The evolution of the rear rotor is a good example. An 1981 GSX 1100 OEM rotor weighing 2,145 grams compared to a 1986 GSXR 1100 and then to an aftermarket 1986 GSXR 1100 rotor weighing 533 grams, the aftermarket rotor = 75% lighter than the OEM rotor!

Rotors by Max Mutarn, on Flickr

The 1981 GSX 1100 OEM rear brake system;

rotor and bolts
torque brace and bolts
caliper/mount/bolts
brake line/banjos
master cylinder/res/bolts
brake pivot
brake pedal

total weight is 5,376 grams.

After swapping the OEM brake parts with modified and replacement parts the total weight for rear brake parts on this build is 2,592 grams, less than half the weight of the OEM system.

[Grimly]

Caliper with its new titanium bolts from the "Ti bolts spares bin" to complete the rear brake system overhaul. Only two main jobs remaining, some final wiring to sort out and tune the carbs.
Rear brake 5 by Max Mutarn, on Flickr

Always thought the entire GS rear disc series were over-braked anyway.
Nice way to solve that problem.

[Shin-Ken 1074]

Installed the rear caliper and master cylinder today, bleed the system and it is working as advertised, could come in handy one day? Brakes, what a drag!

New pistons and seals fitted to the caliper, new pads installed and new overhaul kit fitted to the master cylinder along with a new brake line.
Rear brake 1 by Max Mutarn, on Flickr


Slow going topping up the master res 15ml at a time while bleeding the system.
Rear brake 2 by Max Mutarn, on Flickr

Rear brake 3 by Max Mutarn, on Flickr


System bleed and holding pressure when the brake is applied. So far so good!
Rear brake 4 by Max Mutarn, on Flickr


Caliper with its new titanium bolts from the "Ti bolts spares bin" to complete the rear brake system overhaul. Only two main jobs remaining, some final wiring to sort out and tune the carbs.
Rear brake 5 by Max Mutarn, on Flickr

[Shin-Ken 1074]

Picked up the new pads today and now the rear caliper is back together at last. Tomorrow should have the overhauled rear caliper, new brake line and master cylinder installed.


OEM pads by Max Mutarn, on Flickr


Caliper 20 by Max Mutarn, on Flickr

[steve murdoch]

"Ti bolts spares bin" is a phrase i didn't think i would ever hear.

[Shin-Ken 1074]

Having a few spares bins can be very helpful to keep these vintage GSX Suzuki machines running, ya never know what part will come in handy at short notice. Like when working on a part and you discover two steel bolts on the rear caliper could be replaced with Ti bolts from the "Ti bolts spares bin", got lucky on that one.

Spares Bin 1 by Max Mutarn, on Flickr


Spares Bin 2 by Max Mutarn, on Flickr

[Rob S.]

"spares bin", gotta be the metaphor of the week

Yeah, I could confidently state that my spares bin never had any titanium.

[Lorenzo]

...[there were two titanium flanged M10 x 45 mm bolts in the spares bin]...

"spares bin", gotta be the metaphor of the week