750 Katana Resurrection

[Forden]

this build thread is a real education in itself, thanks for sharing your work in such detail--you say it's therapy, well, I thank you for sharing your time on the professor's couch.

I could never quantify the time I have spent fishing, either... probably best not to think about it too hard.

[KiwiAlfa156]

Thanks Forden, that's very flattering. Just sharing the journey and posting what I think is interesting. Hopefully others, such a yourself, find it interesting too.

[KiwiAlfa156]

Pretty much finished the inlet ports. Got some valves coming to replace some that need to be swapped out.


Tried to take minimal material out as I'd like to maintain as much port velocity as possible. Also left the throat area as undisturbed as possible apart from cutting out the casting flaws on the long side and blending a gentle radius back into the bowl. On the short side I radiused it as best as possible, removing the sharp step which is ringed in red below. Again removing minimal metal.



Cleaned up the casting core flashings in the turn of the ports and blended then into the throat area. The bottom pic above is one done, and one to be done. Surface finished in 80 grit.



Fitted new roller bearing on the clutch release shaft. Never regretted buying a hydraulic press..

[KiwiAlfa156]

Exhaust ports cleaned up. A couple of the inlet valves are badly cupped on the sealing face. It looks like the valves have been heavily lapped on using an electric drill. Replacements on the way. A serviceable inlet is shown for comparison.



I'm using a marker pen as a substitute for engineers blue to reveal and measure the seat contact width. The inlets appear to be over the 1.1mm limit. As do the exhausts.

[KiwiAlfa156]

Ugh: These days someone has always been there before you.

Ain't that the truth

[KiwiAlfa156]

Got a spare 17" Eneki rear for the 750. It's marked "MT" which as far as I know is 'motorcycle tubeless' Of course being early 80s and not being specifically marked as tubeless it has the right rim profile but won't take a tubeless valve stem.



Counterbored a face for the valve stem seal. And used the metal valve stem face with some grinding paste to remove the cutter chatter marks.

[KiwiAlfa156]

Cases split. The rotor/fly wheel wasn't coming off with heat and some pretty heavy slams with a slide hammer. As there's no oil seal or anything to replace, I'll just leave it in place.

So clean, measure, paint and reassemble.

[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?

[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]

Will start loading the cases shortly

[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.

[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]

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.

[KiwiAlfa156]

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

[KiwiAlfa156]

Update.

Clutch in.

Valve seats recut



Cylinders honed



And painted



Next, head assembly and valve leak testing