750 Katana Resurrection

[KiwiAlfa156]

Engine torqued into place. Next step correcting the steering head twist. Had to hammer the front engine mounting plates flat as they were bent. Was really pleased that all the engine mounts aligned which means my internal box jig worked as intended

[KiwiAlfa156]

Squish clearance measured at 1.00 mm exactly. At least the stud will be easy to remove....



This one has obvious necking. I'll have to measure the others. The head had only one locating dowel fitted to position it on the barrels. I guess the tons of tension stopped anything from shifting. I can't tell you how many times I've cursed whoever butchered this bike. Then for the price I really shouldn't complain. I've been looking for evidence that the cases have split. So far no witness marks to suggest that the PO got that far. Hopefully no fresh horrors await.

[KiwiAlfa156]

Not perfect, but good enough.

[KiwiAlfa156]

So.... I thought I might measure the squish clearance before the head and barrels go (eventually) to the auto engineer for a skim. So I placed some some solder strips in the front and rear squish areas on top of the piston, put the head back on -as best I could- and turned the crank to squash the solder. It seemed to spin too easily and I noticed the cam chain wasn't moving. Took off the ATU and found this.



Seems the drive pin was replaced with a small wood screw and a load of crappy epoxy.



Looks like the remnants of the pin are still there as a drill doesn't cut it, so I'm thinking it's tool steel, which the wood screw wouldn't be. So out with the diamond burs I used to get a broken ezi-out out of an outboard motor.



I think I might make a pin out of an old drill bit. The slot in the back of the ATU is 4mm. It should be plenty strong enough as the pin isn't subjected to shock loads.

[KiwiAlfa156]

Seems that the torque wrench comment was truer than I'd hoped for. All the other head nuts where so tight I had to use the half meter+ power bar to get them loose, while basically standing on the gearbox. All good until I found two of the 'dry' head nuts had been to rounded probably by being over-torqued with the wrong sized socket. It took tapping in a 9/16" impact socket and and using my gruntiest 1/2" rattle gun. Even then it took a good 20 seconds of hammering to get them to move. The last one came out with the stud attached... I'm going to have to check the remaining studs for necking.

[KiwiAlfa156]

I thought the screw that goes into the top of the nut was stripped, but it was the entire stud spinning. At least the PO left it in there.

Looks like the existence of the torque wrench was unknown to the PO....

[KiwiAlfa156]

Did some research and the 1100EZ inlet cam has the same part number as the 750. The sprockets are different. I thought I might have one in a parts box, and found a match. I also found a matching exhaust cam. Both hare in better condition on the lobes and journals.
Just need to swap the sprockets.

Thought I could use a spare 1100 rocker arm, but of course the 1100 and 750 differ in valve stem spacing. So I'll have to source some of those...

[KiwiAlfa156]

Jig pretty much finished. I have a crossbar to fit to which the ram will push at 90° to the centre beam.


Final checking will be front axle centreline alignment. The defection is approximately 15mm at the axle.


I've begun pulling down the top end -which was always part of the plan- to make fitting and removing the engine easier for the straightening process.


Already a few issues have become evident


Inlet on number 2, is number twos

[KiwiAlfa156]

Frame jig 2 is coming along nicely. Used a plumb bob and spirit levels to centrepunch some centreline reference marks on the frame and swing arm. The datum was string lines off the sides of the rear rim -checked square against the swing arm piovt- and pleasingly this mapped the exact centre of the swing arm pivot and frame cross tube. Did some diagonal measurements between front engine mounts and the swing arm and they were identical I have confidence that apart from the tweaked steering head, the frame backward from there is straight.



So after some more sitting, staring, and imagining the forces I'll be applying and paths of transmission, I cut some steel and did some arc welding. The chassis with engine bolted in forms the rigid mass for the jig frame.



I'm going use my push ram as I can't get a pull ram under NZs lockdown. There will be an arm for the ram to sit on and push a heavy tube dropped through the steering head. The idea is have the ram operating as close to the horizontal plane of the jig in order to increase leverage on the steering head and minimize leverage and torsion directed through the jig. There will be some triangulation to resist the main jig beam bending.

[KiwiAlfa156]

Straight forks fitted and tweaked steering head confirmed. Next steps degrease the engine, build straightening jig, refit engine and reset the steering head.

[KiwiAlfa156]

Wheels cleaned up better than expected. Tyres were a bitch to get off. Ended cutting the front one off. Hard old rubber and cool temperatures. Next step to get the wheels and frame bolted together and run some strings to check alignment and then decide whether to build the straightening jig.

[KiwiAlfa156]

Reassembled the forks. Replaced the worn bush. It needed a little filing of the end gap of the bush, as the insufficient gap meant the bush sat proud and the fork tube couldn't be inserted. Set up the cartridge emulators with blue springs and 3 turns reload, which is baseline for the Katana. Fresh seals and 10wt synthetic oil, emulators and springs in and the fork caps won't go in deep enough to bite the thread....

Upon inspection the alloy sealing buttons are binding in the top of the fork tube which has an internal taper up the top starting below the threads. Measurements with internal and external calipers revealed the difference was around 0.1mm so the aftermarket tubes have slightly thicker wall thickness.

The easiest fix was to reduce the diameter of the button by 0.1mm, but I don't have a lathe. So I came up with a solution with what I had to hand: plastic pipe, some wooden dowel, tiny panel pins, hand files and emery paper. The buttons are essentially static, when fitted, so while roundness and clearance is important, precision tolerances aren't required.







Kept taking off fractions until they fitted the tubes and the caps could be screwed on without resistance. Reused the standard orings as they were in good nick and had enough give not to jam or twist. A little rubber grease for assembly. Tested action of preload adjuster, and all good.


Done

[KiwiAlfa156]

Clean enough for street use.

[KiwiAlfa156]

Damping tubes drilled


Legs prepped for polishing. Hopefully forks will be finished tomorrow.

[KiwiAlfa156]

Fork disassembled and cleaned


Out of the parts washer


Worn bush next to one from the spares box that dates back to the late 80s...


Comparison with replacement aftermarket part. Some minor differences, but correct where it matters.


Bend apparent on the glass plate.

Next step to polish the lower tubes. Drill the damping tube orifices - I have a set of fork cartridge emulators I was going to fit to the 1100, but I think I'll keeping her as standard as possible. So into the 750 they go.