750 Katana Resurrection

[Hayabuser]

I have a soft spot for orange Kats after owning the Wilton 1260 for three years.



Keep up the amazing work!

[Suzukian]

Nice thing is, from reading this thread, you're going to document your results, and that is excellent!!

[Nessism]

I don't think the head and base gaskets crush that much. I have never had a gasket crush that much on any engine I have rebuilt, car, motorcycle, or aircraft.

There is a first time for everything...

IMG_1930 by nessism, on Flickr

[Suzukian]

I don't think the head and base gaskets crush that much. I have never had a gasket crush that much on any engine I have rebuilt, car, motorcycle, or aircraft. You could always make a test jig, and using a torque wrench, use a piece of gasket material, replicating a gasket seal, and two equal size flat plates, with the gasket material around the perimeter, then torque them together. I don't think they will crush that much. I knew a guy who rebuilt Rolls Royce engines, they actually use a special thread with a very thin Rolls Royce goop to hold the thread in place, The thread is applied in the middle of the surface contact areas around the perimeter, and cut to meet right at the end. The cases are then torqued together. You are doing a fantastic job on this bike. I have read the whole thread and am quite amazed. That first ride you do will be quite thrilling for you, and rightly so.

[Suzukian]

A labor of love!!! You could glass bead blast the tops of the pistons, then polish with Jewelers Rouge, they would shine like chrome and you would get better air flow. Impressive thread to read. This is one of the few bike that will always be remembered and be a collectible. IMHO

[KiwiAlfa156]

Torqued the head down on the old head gasket and new aftermarket base gasket. Squish clearance measurements were too tight.


There was some variation from cylinder 1 to 4 with 1 being the tightest at 0.65mm (0.025") and 4 being at 0.70mm (0.027") so a 2 thou variation... So it seems that the barrels aren't perfectly parallel to the base. The 2 thou variation is over a distance of about 400mm.... So...

The aftermarket base gasket used to check the squish prior to final assembly measures 0.5mm (0.020) crushed. The old head gasket used to check (which is a MLS type) was 1.1mm (0.043) crushed. I have no idea what the thickness of the original base gasket was, and upon which I took my original squish clearance measurements. The virgin aftermarket head gasket has an uncrushed thickness of 1.3mm. This gasket is made from NI-2098 which has a compression factor of 15-30% at 5000 psi clamping pressure (ASTM F 36).



I have some 0.8mm fibre oil jointing gasket sheet, so proceeded to make a thicker base gasket.



I don't know the compression percentage of fibre but this is usually around the 20% mark. The new head gasket should crush out to +/- 1.0mm so I'll re-torque the head down on the new base gasket and recheck the squish. My target is 0.75mm (0.030).

I'm hoping the sum of the gasket compression will get me close.

[KiwiAlfa156]

Progress. Head painted after new valve stem seals and liquid leak test






Spent half a day scrubbing the pistons. Especially cleaning crap out of the top ring groove. Checked end gaps and fitted the new rings to the pistons.



Pistons back on the rods. Barrels thoroughly cleaned after honing. Barrels back on the crankcase



Next squish clearance check (barrels were planed 0.15mm), fresh head gasket and completion of engine assembly.

[KiwiAlfa156]

Update.

Clutch in.

Valve seats recut



Cylinders honed



And painted



Next, head assembly and valve leak testing

[KiwiAlfa156]

Progress. Had to helicoil one of the front engine mounts. But apart from that all good.

[KiwiAlfa156]

I've been hearing lots of good things about this anaerobic sealer lately. Is it new? I'm gonna have to look into it and put some on the shelf.

I don't know how new it is. Loctite do one as well. It's solvent resistant and is all good temperature range-wise. Blurb says it's ideal for sealing gearboxes. Looks ideal for engine cases.

[slayer61]

I've been hearing lots of good things about this anaerobic sealer lately. Is it new? I'm gonna have to look into it and put some on the shelf.

[KiwiAlfa156]

Finally got some garage time. Time to reassemble the bottom bottom end.


Assembly lube (moly) for the crank bearings.


Shortened an 126 link cam chain down to 122

Upper case loaded. I'm using an anaerobic sealer on the case joint. This stuff stays liquid until its clamped down and starved of oxygen and then it cures between the mating surfaces. Excess is easy to wipe away and internally the engine oil washes uncured sealer away.


I applied it with an artist's brush. It is evenly applied, but the glare from the lights makes it look patchy.


All torqued up. Not too much excess.


Next step is get the crankcase into the chassis (before it gets too heavy) and then clutch, piston, barrels and head.

[KiwiAlfa156]

Will start loading the cases shortly

[KiwiAlfa156]

Some progress while recovering from Covid. The inside of the engine was pretty dirty with firm sludge remaining where the particulates have settled out of the oil as it sat cold for the last 10+ years.




So I spent a couple of days cleaning the cases inside and removing lose paint, oxide and residual dirt.





Reassembled the empty cases, masked up, grease and wax remover, primer grey and the semi-gloss black engine enamel.

[KiwiAlfa156]

Looks good. I was there a few weeks ago installing a new output shaft.

Yeah, it is looking good, Crank journals look pristine and lightest of wear marks on the shell bearings. Gear teeth show next to no wear, selector forks ditto. Looks like the cases have never been split. Given the ham-fisted work on the top-end, I needed to have a look to quell any doubts and I'm really pleased at the condition of the bottom-end and gearbox. I'll check all the bearings, give everything a clean and paint the cases, and start the reassembly. What was the issue with your output shaft BB?