GS650GZ Katana Rebuild (Historical)

[KiwiAlfa156]

I thought I might share the last rebuild I completed here too. The following was also posted on the Katana Australia forum about two years ago as a work in progress. I've edited out the replies and comments so that its more of a narrative. It's complete from start to finish, so its got a beginning, a middle and an end.

So here it is.

Had a look at the 650 today. I bought this for $450 a little while ago, because at $450 for a complete unmolested bike was too tempting to pass by. The owner wanted it gone (or possibly his wife did). There was a new Harley in his garage and house renovations going on. He said the bike had originally belonged to his brother and that the engine had been "rebuilt" but after getting it running, the carburation had been problematic, so he parked it in the back of the garage, meaning to get back to it, but never did. Sounds familiar....


I pulled the plugs which looked new with a little colour on the porcelain but clean, with sharp edged electrodes. I squirted a little oil into each cylinder as the little beasty hasn't run for about 16 years, removed the ignition cover and slowly turned the crank. To my surprise it was buttery smooth. I was half expecting a bit of scraping. But no. Hmmm. All in all it seem to suggest that the P.Os story was kosher (not that I doubted him) and getting her going might not be a mission. Oil and filter change, clean the carbs, new battery might just do it. So I pulled off the carbs -noting that the urethane foam air filter had fossilized - and lifted each slide one by one with my finger and let them drop. Four, 3, and 2 were good, number one however dropped way too fast indicating a diaphragm issue. Pulled the cover and sure enough the diaphragm had been incorrectly installed with part of the outer edge having folded over and creased by the top cover.





Fingers crossed, this project wont require major surgery (and lots of dollars) -unlike the 1100 and the Yamaha- to get a runner. Brakes need work -no lever or pedal pressure, and the tyres are from the 20th Century.


I'm thinking of using it in an unrestored state, to start with anyway. Time will tell where it ends up.

[KiwiAlfa156]

Further stripping the 650 carbs for cleaning revealed another potential problem. The pilot jet in No.3 had been butchered by someone in the past, with the screw slot completely gone and the orifice looking a bit buggered too (not that I claim to be an expert on buggered orifice assessment, but it looked fooked to me). To get it out, I had to drill out the orifice slightly larger and then carefully tap in a small jewelry screwdriver in so that it could be used (with the help of a pair of vice clamps) to unscrew the jet. This worked and the offending jet was extracted without any damage to the thread in the carb body.


...Carb bits on their way this week. Did a test refit on the creased diaphragm, and it operated correctly when installed properly, so a good clean, set the float levels, fresh oil and we'll see if she starts. Peered down the inlet tracts with torch and the valves where spotless, so this puppy didn't run for long after it was fettled with all those years ago. The inlet manifolds on the 650 bolt to the head with quite a bit of misalignment and steps at the joints. I'm looking at this and thinking, hmmm there's some free horsepower right there. At some stage I might have to get the porting tools at it and give it a clean up.

[KiwiAlfa156]

And it sounds good. No smoke.... No oil pressure light either, but running a multi meter across the oil pressure switch confirmed no resistance with engine off (open circuit), and infinite resistance with the engine running.

[KiwiAlfa156]

Finally started doing something with the six-fiddy. I'm keen to use it as a commuter scooter for days that it doesn't rain (which in Auckland is a lot). The traffic here has got crap as apparently at peak 9000 cars a month are added to the already choked streets and motorways. Riding the bike almost halves commuting times.

I've been starting the 'Patina Katana' every month or so and running it for 10-15 minutes. But with buggered brakes, tyres from last century, pogo sticks for shocks, and a little surface rust on the forks, riding it has been out of the question. I've been collecting bits and pieces and last week pulled of the brakes to pull them apart and start rebuilding them. In the process of dropping the rear wheel, I noticed play in the swing arm. so dropped that out too. The bearings were shot, and having never owned a shaft-drive, got to wondering how to get the bearing races out of the swing arm as the shaft tube means that the races can't be knocked though from the other side. The answer from the internet was to shrink the race with a welder. So after consuming some YouTube tutorials, out came the MIG.

Finally started doing something with the six-fiddy. I'm keen to use it as a commuter scooter for days that it doesn't rain (which in Auckland is a lot). The traffic here has got crap as apparently at peak 9000 cars a month are added to the already choked streets and motorways. Riding the bike almost halves commuting times.

I've been starting the 'Patina Katana' every month or so and running it for 10-15 minutes. But with buggered brakes, tyres from last century, pogo sticks for shocks, and a little surface rust on the forks, riding it has been out of the question. I've been collecting bits and pieces and last week pulled of the brakes to pull them apart and start rebuilding them. In the process of dropping the rear wheel, I noticed play in the swing arm. so dropped that out too. The bearings were shot, and having never owned a shaft-drive, got to wondering how to get the bearing races out of the swing arm as the shaft tube means that the races can't be knocked though from the other side. The answer from the internet was to shrink the race with a welder. So after consuming some YouTube tutorials, out came the MIG.



About to shrink some bearing races



Great success.


Will post more as more gets done.


My plan is to get her as a daily runner and may be tart her up as i get the urge.

[KiwiAlfa156]

My plan was to leave the 650 in its original patina, but the truth is that it isn’t original. Under the ‘casually sprayed’ black of the frame and swing arm is a coat of orange paint that becomes visible when the black is scratched back with a fingernail. The orange paint appears to have been applied to the bare steel without an etch-primer, or any primer at all for that matter. I’ve lived with myself long enough to know that the paint on the frame will bug me. The thought of pressing new bearing races into a cruddy swing arm also gives me no joy

So out with the paint stripper.



There were ‘tin-worm’ tracks on the bare steel.


180 Grit and a stiff wire brush on the air die.


Rust converter and then etch-primed.


Once it’s cured properly I’ll spray the arm in satin sub-frame black. Which I’ve had some success with in the past. So, it looks like I’ll end up stripping her back to the frame and then stripping the frame…. At least the engine doesn’t need to be opened.


I can see one thing leading to another….er….

[KiwiAlfa156]

This game again...




This is pretty much how the loom came of the bike. Apart from about the coil leads north to the headlight, that was wrapped with duct tape from last century. Have already seen an earth wire that has lost a bit of insulation. Testing the wires terminal to terminal with the multi-meter for continuity and then will re-wrap properly, I do have some Nitto self -amalgamating tape and may use this, or get some loom cloth tape (may be a combination of both?). Have cleaned a couple of the connectors using a circuit board degreaser aerosol and the results were startling. After a few seconds and a little agitation, it dissolved corrosion and left bright brass behind with no damage to anything else.


Once the main loom is done, I'll check all the switches, bulbs, etc.


Seriously considering lifting the motor out of the frame..... one thing leads to another....

[KiwiAlfa156]

Loom finished. Continuity tested. A section of earth wire replaced that had lost a fair bit of insulation.

[KiwiAlfa156]

And one thing leads to another. Disassembled, cleaned, tested and reassembled. Frame number identifies it as a Z model, and the tacho, speedo and the 'you naughty, naughty boy' 80 kph+ warning light also ID's it as a JDM. I have hazy recollections that a shipment of cheap JDM 650's being sold in NZ in 83' as they didn't shift in Japan as well as Suzuki had anticipated.





Used Google translate for the sticker on the tacho.


"People touch", they just do Pete. You've been warned!


I quite like how the other warnings are in reality polite suggestions. "Let's wear a helmet", could easily be followed with '...and why don't we do lunch?'

[KiwiAlfa156]

...and one thing leads to another...








Looks like the engine is gonna come out for painting, which means the frame can be repainted





Pulled the starter motor apart as it was a bit sluggish. Found the usual carbonisation on the commutator, so cleaned it and the brushes up. Also discovered that one of the permanent magnets was no longer permanently attached to the casing of the starter motor, had shimmied across to be closer to its neighbour and was being 'gently shaved' by the rotor when the starter was activated. Was an absolute *@%^$*@%^$*@%^$*@%^$ getting magnet filings out off the 4 magnets, but god bless the air compressor. Sanded the back of the magnet and the inside of the case and stuck the sucker back in using Ados F38 high temp glue.

[KiwiAlfa156]

A little more progress. Decided to rub back the frame by hand as there is no rust to be seen. The black appears to have been sprayed over the orange without any surface preparation at all, it was probably cheap rattle-can paint and isn't particularly hard and has variable adherence to the orange. It comes off very easily with 180 grit wetted with meths. The orange seems to have been sprayed onto bare metal but has adhered well. So, I'll remove all the black, spray an undercoat over the orange and satin black subframe paint over that.


Don't really want to disassemble the engine to paint it. Might soda blast it in one piece.... mask and spray. I say that, but this project was supposed to be just get it road worthy, forget the cosmetics and ride it. Then again there is a gasket set for sale...

[KiwiAlfa156]

Progress has been slow due to every other thing seeming to be so bloody important. But managed to get into man-shed for some man-time, completed my hand-sanding of the frame and put a layer of under-coat on.





Next will be some satin sub-frame black.

[KiwiAlfa156]

Sub-frame Black

[KiwiAlfa156]

And a step backwards. Discovered that the sub-frame black wasn't particularly solvent resistant..... In fact, you could pretty much wash it off with turps.... So I did. And after a couple of hours with rags and an old toothbrush we are back to this.



I decided to revert the swing arm back to the original silver





So, I have some satin black epoxy enamel for the frame. Haven't decided on the colour for the bodywork yet

[KiwiAlfa156]

Front tyre fitted and balanced.

[KiwiAlfa156]

A little port alignment might in order.