78 Cb750K - First build

tmtrebor

Active Member
I've been meaning to post this for a while, but just never got around to it, so here it goes.
Gallery here : http://imgur.com/a/K7Jvy

Lost all my pictures from the build, so I'm going to start with what I have and going forward.
I bought this bike 2.5 years ago as a project, and finally have it all together and running again. Initially it worked, but leaked oil and smoked like crazy, so I decided I could just tear it down and rebuild from there, probably a huge mistake, but it's what I did. The build took so long for 3 reasons, I got my MBA during this period, my actual car engine blew up and needed to be replaced, and I found out I had absolutely no idea how electricity worked.

Bike now :
G6WtsST.jpg


The teardown included a full replacement of gaskets, rings, etc. I couldnt find the correct rings for the bike, so I had to get a lightly larger set and used a honing tool on the cylinder for it to fit. According to the redneck in the garage I spoke with, this was fine to do. After checking the compression in the cylinders he proved to be correct, and I'm running at 140-148 in each. I think this is slightly out of spec, but for phase 2 I plan on talking with a shop and the pistons and whatnot anyway. Oil leakage is gone, and the bike no longer smokes!

Other things were the replacement of the chain and sprockets, as the bike sat in this dude's garage for 3 years, and I know my bike chains get rusty from a week of no cleaning, so I figured it was pretty much done. Other things were clubman bars (mistake), some cafe seat from some guy (mistake, as it's too big... I'm selling if anyone wants), some gauges and new lighting. Apparently the bike also had lowering blocks, which I did not know, so I took those off in the pictures below.

Electrical was done with an entirely new harness created by me. This took forever as I kept getting confused with how the lighting system on the gauges worked, and how the blinkers worked. I realized I needed diodes for the blinkers, and how to connect the gauge lighting, and it all works great now. The neutral light does not work, which I guess I have to replace the switch. Any input on how to do this would be awesome.
I "upgraded" upgraded to a solid state regulator/rectifier, built a little electrical box for under the seat (pics coming in next update) and cut the rear end off to prepare for my "cafe hoop" (which I have some questions about).

Anyway, now on to "phase 2" of the build, which includes getting this bike to a rideable state again, and then making it "pretty" during the next year. I'm currently trying to figure out how far I want this cafe hoop to go out. I've read things saying you dont want to extend too far past the center of the rear wheel, so that's what I'm trying to stay at. I have 3 lengths below which I'm hoping one of you guys could say "that's it." If not, maybe let me know to move it in or out :

1)
9jIwBen.jpg


2)
QOv3zTq.jpg


3)
cyjfFCj.jpg


After this I guess I will weld it on then extend the box out to find a place for my battery. Any other suggestions would be great!
 
I am certain you will find a ton of great help here in regards the CB750. There are some great builds on here.
 
Ok, it has been a bit, but ive worked some things out and actually had the first ride since tear down last night (not very far due to no front brake).

It feels so cool to ride something youve built, even if its a little ugly now.

So, what has been done since last post?

I added a rear hoop with a hidden battery tray. Make fun of the welds if you want, first time welding and i know they are ass.


After realizing i sucked at welding i decided to practice on some scrap from the chop up.... i feel like they were a little better... tips would be great.

Next step was getting the seat on, which was fine since i had fit it before.

Then, maiden voyage time!! But ran into an issue. I had replaced the clutch wrong. I found some incorrect info telling me to use one less friction plate in the clutch pack, so i did and experienced clutch problems. Luckily tunafish here corrected my ways, and im now rolling!

Next day... tried to go, having issues starting and fearing its electrical... turned out to be a crimped fuel line. Fixed it and it started to rain.

Fast forward to yesterday and its go time. Maiden voyage! Here she is, dont get on me about wiring please, cleaning that up this weekend. Was too hyped to get a window to ride before the rain.

Suggestions/comments/criticisms welcome as always!

Next step is new/cleaned up seat, pistons, engined cleaned, etc. And front end from an r9 or gsxr.... havent decided.



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Kamn said:
I take it you solved the clutch problem??
Oh yes. I learned ignore all things you search for unless you ask on dtt (or know what you're looking for) So many people dont put model or year. I think the bike info i looked at was for a 76 or something, as the double metal clutch plate wasn't in those from the factory.

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