CB750 K0/K1 Hybrid

[Jonesz]

Good to hear that the replacement part is not "unobtainium". While expensive looks to me like the Yamiya part will provide peace of mind rather than welding the cracked oem one. At least you found the crack before proceeding too far into the rebuild.

[Lucien Harpress]

Three things that make this annoying:

-I had the D-washer in place. It cracked anyway. Maybe it was a bit thin, but best I could tell I had the stock part.

-It's not cracked all the way through, but at the same time it was NOT cracked when I painted it a couple years ago.

- I had a spare back when I parted most of my '71 roller out. I didn't think I needed it because mine was good (see above) and I got a good price for it.

It's annoying more than anything. I'm eager to get it back together. Thankfully it looks like the Yamiya part is made of better metal than the old ones, so the peace of mind will help. And one less part to paint.

EDIT: Went ahead and grabbed a Yamiya unicorn triple tree. I had someone over on the SOHC site offer me theirs, and the price was more than reasonable. But with shipping it would've only been about $20 less than the replica, and maybe I'm a bit gun-shy about the whole endeavor, but an intact 50 year old part prone to breakage is still a 50 year old part prone to breakage. Twenty bucks more is worth brand new (and made of better materials) to me.

Swingarm bushings and steering head bearings arrived as well, so those are ready to go. I ordered the paint for my last couple parts that need it (side and center stands, various brackets and hangers), so once that arrives things should start moving again.

[Lucien Harpress]

Work continues. I'm getting super-close to a lot of big progress. The only thing holding me back is getting a couple critical parts painted (center stand and triple tree), then I can start swapping parts in earnest. Unfortunately, because I'm using a two-part spray can, you only get 24 hours use out of a can, so I have to collect as many parts as I can and do them all at once.

Adding to the fun, I started the day attempting to clean my center stand for paint. But paint starting coming off with the dirt, so now I've got to get primer as well.

In any case, I started breaking down my roller frame some more.

[pidjones]

For such parts, I've settled on etching primer (the olive drab from Rustoleum or Duplicolor) and Black Appliance Epoxy (which is NOT epoxy) from Rustoleum. Not quite as tough as 2K, but either will scratch in these applications. The Rustoleum nozzles are a biotch to press, so be prepared for sore fingers. I broke one of the plastic add-on triggers on them. But, it is one of the toughest 1K paints and lays down nice. Two day easy handling cure in warm dry garage. After a month or do is fairly fuel-proof (sorry, not brake fluid proof). Available from Walmart, Big Box stores. I save the Spraymax for tins.

[Rednaxs60]

Spray can nozzles need to be considered as pidjones mentions. There are easy spray can nozzles that give a good spray pattern, and there are the inexpensive, not so easy to use that do not give a good spray pattern. here's a picture of three spray nozzles:

Spray Can Nozzles.jpg (344.43 KiB) Viewed 1209 times

I found the one in the middle gives the best spray pattern and was the easiest on the fingers. It can be adjusted for horizontal/vertical spray pattern. I used the Rustoleum product when I did my '85 Limited Edition. It works well on the switch housings as well. The standard spray nozzle on the left can leave "tiger stripes" (all can but this one especially) I believe they call them, and the one on the right is better than the left one, but not as good as the centre one.

[pidjones]

True, but the one in the center only fits cans with a male protrusion (and recently have too short operator shaft in them, but that can be replaced). The kind on the right can be purchased on Amazon as well as others. The "taggers" (graffiti artists) have driven quite an industry in this it seems.

[Lucien Harpress]

I'll be the first to admit, the paint on some of these parts may be a bit overkill. The center stand comes to mind- it's technically a wear item, so two part paint might be a waste. On the other hand, I've gotten bitten by the "Well, since I've got it apart...." bug REALLY hard, so the stuff that's a pain to get apart (frame, triple tree, engine hangers, etc.) is getting the good stuff. While I've got it out, though, I may as well get some extra bits done as well.

The paint strip on the center stand was a bit of setback though- otherwise I'd hit everything I had this weekend, and potentially get the wheels on by next week. Primer and weather sets that back a couple days, but....

Listen, I'm just antsy to start putting on parts that aren't black or silver, okay?

[Rednaxs60]

I hear you. You get to a point where you tell yourself "enough is enough". It feels good when parts start to go back on.

[Lucien Harpress]

Primer arrived early. Let's go.

[Lucien Harpress]

I have done 4 sets of steering head bearings. I still absolutely hate doing them.



That said, obviously parts are starting to go back on. New roller bearings are installed, and now every bike I own is set apart from the small ones (Solex, CT90) or disassembled ones (Dream).

As an added little bonus of fun, I managed to find an early seat latch for surprisingly cheap. I was fully prepared to keep the 1972-and-onward locking seat latch, but while the K0 sidecovers DO fit, they were worrying close to the latch. I could just see myself scratching the left sidecover eventually. Of course this meant I had to replace the seat as well. Which I have- but pics of THAT can wait.



I actually prefer the old style latch. It's a bit cruder, but more subtle as well.

Next goal? I've gotta plate some bolts tomorrow, then it's getting that center stand on.

[Lucien Harpress]

Lot of progress, a majority of it good. I am happy to report that not only is the 750 finally standing on it's own legs again, we have our first official install of blue parts!





I've also made what I'm hoping is the final large purchase of this build. I was going to wait on updating the gauges, because I can literally swap those out whenever. But I had the money, and once again I figured "while I got it apart, I may as well..". So, I've got new housings, face plates, neutral/blinker/etc. light jewels, and rear plates headed my way. The only part I'd need to built from scratch are the light tubes for the idiot lights, but that shouldn't be hard.

But, of course, there always needs to be a downside. In this instance, I figured I'd pop the bands that hold the gauges on, as a fun little last detail for the day. They're held on to the top triple tree with three screws, and because my (new) top was powdercoated, I'd need to tap the holes. No problem. Well, one must of had some gunk still in it (even after blowing it out), because the screw did that thing where it started tightening up AS I was unscrewing it. I ended up full worst-case scenario- snapping it flush.

Through some minor miracle I manage to drill out and remove what was left of the screw without damaging anything that would be visible with the gauges in place. The BAD news is that I've got this big goober of a hole I've got to somehow make usable again. Helicoil is the reflex answer, but I'm not dealing with that today.

(Note- the edge of the hole looks light it has a lot of garbage that needs cleanup. That's just the light. The edge of the hole is flush. That's just all the chipped powedercoat. It's not great, but not as bad as it looks.)

[Lucien Harpress]

Parts are starting to roll in, so progress has been rather swift lately. First up, new swingarm bushings.



Shockingly enough, this went better than I was expecting. The old bushings didn't look too bad, and even drove out relatively cleanly. The center pivot shaft, unfortunately, was TOAST. Patches of what looked like REALLY bad water damage. It was definitely my problem. Thankfully, I had a spare in better shape, and everything went back together painlessly.

The plan was so get the wheels on and roll the frame out of the barn and into the garage, but a bunch of holdups on the rear wheel (polishing the brake side, getting a proper replacement rear sprocket) led me to fill time by tackling other areas. Most of which are now... done.





Electrical is in and (apart from gauges and connecting everything in the headlight bucket) done. Since taking these photos I've also got the headlight on the oil tank installed. I may not have all the detail parts I need in time for Gilmore, but assuming I have no running issues it should at least be ridable by then.

[Lucien Harpress]

After wasting WAY too much time waiting on a new rear sprocket (twice!), I finally managed to wheel what I have out of the barn and into the garage where I've got a bit more space.





Best I can tell, I'm out of things to order. I could probably get the carbs on right now as well, but I'm confirming a couple things before I do. (Because this bike has always been bits, I'm trying to see what the best jetting would be for newer carbs with older exhausts and airbox) Gauge parts are set to arrive this week, so hopefully I can get those rocked out. June 11 is still going to be tight, but still possibly doable.

Just for fun I decided to throw the tank on. I like it.

[Rednaxs60]

Looking very good.

[Lucien Harpress]

Some good news, followed by some really, REALLY bad news.

First up- we got 'er done enough for a shakedown run! I'm still missing details here and there (proper bolts, an oil switch), but it was complete enough to get it started, and run about 15 miles.

https://youtu.be/5FpZhi5wC7Q





But, of course, now for the bad news. About 12 miles in (after running great all that time), it started to not want to idle. Engine speed would gradually slow, until it started cutting out. My last couple stop lights consisted of me keeping the throttle cracked to keep the bike running. Once I got it home I noticed it was an absolute pain to kick at all, like I was fighting more than just compression. And to top it off, fishing around in my oil tank netted me about a tablespoon of non-magnetic metal shavings.

Long story short, 6 months of work got me an engine that's eating itself.

So yeah. I'm planning on draining the oil to get a look at it tomorrow, but I've got a feeling at least one of the main bearing shells was too tight. I plasti-gauged it before buttoning up the bottom end, but I would bet money my crank wasn't round, so it messed the results. And I simply don't have the tools to measure this stuff accurately enough.

Ah well. I'm not happy, but there isn't much I can do about it. I'll probably do what I should've done in the first place and find a good donor motor (even if it's just a workable bottom end). But that can wait for a bit.