Topic: My first bike. Amateur CB750 rebuild.

[nitsua93]

I picked up a cb750 k7 on Craigslist last week. Never really heard of them before, but I'm also very new to the motorcycle scene. I'm trying to do a mostly stock restoration with the exceptions of, drag pipes, drag bars, and probably a big bore. I've never restored anything. I've also never torn down an engine with the intent of putting it back together in running order. I'll have some question at the end of this post! Please help with them!

A little bike history: It's been sitting in a barn for 30 years. That's all I know. Was purchased new in 77 and the last time it was registered was 80.

Here she is the day I picked her up after removing a jerry-rigged cargo box and a 77-80 Honda shadow faring.


Used a winch to lift up the frame to I could drop the motor out. Took much longer than it should have.


Bad news: That engine also sat for 30 years, somehow exposed to weather. The pistons took in a lot of moisture and were all absolutely frozen. Tried for a couple days to get them moving and no luck

Oh well! That means I get to buy another!
Picked up this one which has so far been in pretty good shape. Except for a sheared bolt holding the case together I'm having trouble with that.


Got these pipes with the new motor!


This weekend I should have the frame blasting done. Ill blast the bottom of the seat and blast whatever else I can.


Now for my questions!

There's a sheared bolt holding the case together and I'm not sure how to get it out, should I just drill it out and then re-tap the hole? I'd really like to inspect the innards of this sucker.

Is a 83xCC kit worth it compared to the stock 756cc?

What jets should I use with the open drag pipes? I have the original k7 carbs.

This is my first bike, and my first project. I'm an automotive tech student in college right now, so sadly all my funds can't go to the bike

I live in Central Indiana, just north of Indy. If anyone near me can help on this bike that would be awesome! Also, beer is not a tool with this bike :p I always see beer in everyone's builds!
Here's my rice burner.

[rusty2078]

for the bolt: start with a center punch and mark the top of the stud, then start with small bits, working progressively larger in diameter, being very careful not to get off center/off vertical with your hole (or you risk messing the threads up.....ask me how I know). Get an "easy out"/stud extractor (square and edged tapered punch that bites when you set it with a hammer and turn it counter-clockwise. Take your time with it, if you get in a rush, you'll probably mess up threads. If you're really not in a hurry, what I've done before (varying success) is drill out as much as possible and then heat with a small propane torch/let it cool/penetrating fluid...repeat/repeat/repeat. The cycles of heating/cooling sometimes are enough to "break" the threads loose. I do this because I really hate tapping/heli-coiling.

[Free Booter]

I dunno. I always found Pilsner Urquell or Stella Artois extremely useful tools...?

[70CB750]

I dunno. I always found Pilsner Urquell 

Yes!

[SOHC4 Cafe Racer Fan]

Interesting engine removal method.

[nitsua93]

I bought a new.engine case. That one had some issues.

Question: Would it be beneficial to put my K7 cam into my K2? What about putting the valves and springs in there too?

Sent from my HTC One X using Tapatalk 2

[nitsua93]

I've now got a couple questions.

I cant seem to find a carb rebuild kit specifically for a k7. Is it the same as a K6?

Also, would there be benefits of using a k7 camshaft and all the valve stuff on a k2?

[ampsrampstramps]

Don't take my word for it but from what I could find the K7 (not knowing year) used Keihin PD41A carbs. Check the side of the carb for a number and search for a rebuild kit based on that. Cool looking bike. Good luck!

[nitsua93]

Will do, thanks! I finished putting the transmission back together. I've got to to order my gaskets and slap this sucker all together!

Sent from my HTC One X using Tapatalk 2

[nitsua93]

Update! I just ordered everything I'll probably need to finish the bike, except I forgot to ever check the clutch :p

I put the bottom end back together! I then decided I'd soda blast the case so some of this may come back out. I had a freakin heck of a time putting the transmission back together, it really sucked. It probably took me 20 minutes to get that stupid neutral switch to squeeze in, but after the first time it went in and out pretty easy.



This is the cleanest plate on the bike.



The other plates



Right now I'm trying to clean up the chrome. I'm soaking a bunch of it in vinegar overnight, and if that doesn't work I'll try a couple of the recommended aerosol treatments.

[nitsua93]

Another question, I have the stock k7 carbs. Which of these rebuilds will work? They all skip '77, except for the F model.
http://www.newmotorcycleparts.com/fuel_system_parts/carb_kit_hon.html

Edit: I've read about people hating these carbs, should I just replace them with something more popular?

[Stev-o]

The K7/8 carbs are diff than the earlier models. I have a K8 and have no issues with the carbs.

[nitsua93]

I'm trying to get the motor running on a test bench. Having a little trouble of course. I can get the starter to turn. I'm not sure if I'm getting spark or not, I have to use a test light and check. I can't find any info on how other people did it. I can only find videos of them running, not the setup.

Sent from my HTC One X using Tapatalk 2