Topic: Another SOHC/4 project... 1973 CB750

[ChevelleSSLS6]

Hello again,
I used to post here back in 07 about a cb550f, but I sold that to a collector, bought a new kawasaki ninja 650 (it's basically a standard bike with sportbike fairing) and was happy with that, visiting back occasionally.

Then, my brother is home from the Navy for three weeks on leave.  He has (it's really dad's but he says my bro can have it) a 1973 Honda CB750.  Here's some pics.  Tell us what to do and how to do it....  The carbs are different than on the 550 and the small engines I've wrenched on, so this is a whole new world for me.

Enjoy the pics.



















...one of the pics is of my humble collection of tools and the other is a lift kit destined for my Jeep... those will come soon hopefully as well.
-Matt, 23 and brother Tom, 26

[HondaMan]

Looks like the tank is toast.
Does the engine turn over?

[ChevelleSSLS6]

engine: good compression... it did run a few years ago, so I'm thinking it doesn't need much.  I'm not sure how to remove the carbs and stuff as they linkage is different and all from the 550 I had, and my ninja has FI so I never touched that yet.

Where is the line drawn from 'viable project' and 'rolling parts bin'?

Any ideas on the tool kit (especially the tag reading 'cb 1000 c')... I wonder if this is not the correct tool kit....

Off topic and all, but personally, I feel bad about the high revving SOHC being forced into Goldwing-esque duty on this 'touring-ized' motorcycle...  Restore it (maybe some mods) or cafe it!

[Toxic]

Go to Inspiration Galery thread, pick a style you like,then access 5 grand for stuff you'll need to create one of those beuaties.  Then read this fourm about ten times a day. 

You'll pick up alot of info here.

Good to see  a bike like that being brought back to life.

Make it special and make it "yours".

[Alan F.]

First off, it's far from a pile of parts, Have No Fear!

That tank may not be toast if it doesn't leak.  Run a search for 'the works' tank cleaning rust, and the practice of using a baking soda solution to neutralize the acid and prevent flash rust.

The wiring is almost certainly compromised from stock, but if it works and seems reliable go with it at least for the short term.

Did your Dad build the bike?

What you do to the bike should be dictated by what king of riding you do, or plan to do with it.  Save those bags, someone here or on eBay will go for them.

The possibilities are endless at this point, limitted mostly by imagination and cash on hand. 

I'd recommend being sure it'll ride safely, if you strip it down look at all of the frame welds for cracks or repairs, Install a tapered roller steering bearing kit, Have the swingarm bushings done by Hondaman, replace all of the wheel bearings and seals, spokes, tubes and tires. Rebuild the forks, and get some new rear shocks.

Replacing and upgrading these things will give a good safe and solid base for whatever you can imagine to build it into.
Cheers, and good luck.
-A

[USN20]

A good start for your K3 would be to have:

1. Owners manual - familiarize yourself with the bike and basic adjustments.

2. Parts book - Honda part numbers and exploded views.

3. Shop manual - How to disassemble / re-assemble components and torque specs.

4. Tool kit - Replace your missing tools ones as the kit does come in handy.

Resource from the SOHC forums: http://www.sohc4.net/index.php?q=content/cb750

[Old Scrambler]

Yes to all above about getting manuals and gaining knowledge already posted on this site...........My first mechanical move would be to remove all of the bags, windscreen, and associated brackets.  Then try to source the original tail and head lights that your Dad probably stashed in a box.  It appears that the typical mild oil leak is present at the head. Many owners just clean this up and live with it. Your Dad did for many years.  Otherwise, it will require the removal of the complete motor before you can remove the head and install new o-rings, cam holder pucks, and the head gasket.

If the bike was running a few years ago, the carbs are probably at or very near the required settings. Following the instructions in the manual and from this site about the complete fuel system.  Then get a new sealed battery and a new (or clean) air-filter, and give the motor a try.  Before riding, remember to check all of the other systems for safety. If you get it running, don't expect it to run as new.  It may take a few hundred miles to push enough fuel through the system to bring it truely back to life as it was in 1973.  Also, be aware, a lot of the K3s came with 105 main jets and did not perform as well for overall speed and power.   Your Dad has a 4-1 exhaust and may have changed the jets to 120s. 

I have a K3 that I bought new.  It has been modified for many years but is now returned to stock.  Good Luck

[ChevelleSSLS6]

I'm not sure what my dad did to this... besides the wood dash.  He says it has no second gear and 'needs a shop to look at it for it to run right'.  He did buy it from a friend of his who was more of a modify-it guy (dad is a 'its stock and good enough' type who is not a fan of the neighbor's screamin' eagle muffled HD), so I'm thinking this friend did a lot of the mods before selling it to my dad.  He might have the original lights.  I'll have to see if I can get a hold of him.

It'd be a comfortable 'vintage sport tourer' with the stock forks and lights on it though.  Those trunks have a lot of room too!

In the end, it's up to Tom, as it's 'his' motorcycle.  I'll have to show him this, as he thinks I can just jump into it and get it firing on all four.

[fmctm1sw]

Where is the line drawn from 'viable project' and 'rolling parts bin'?

I've called much worse looking a "viable project."  Call it optimism!

[Johnie]

Agree with all the above, especially get yourself a Honda service manual.  You can find one on eBay or try www.helminc.com  I agree with scrambler and would remove those bags, trunk and shield.  Along with all the other aftermarket stuff.  But before you go to far you have to decide what you want?  I am a stocker guy and like to restore these to the way they looked in the showroom.  Maybe you are a cafe guy, etc.  So first decide what look you want and what you can afford.  Do not be in a hurry to fire it up until it is ready.  My KO sat 17 years and it took me 3 weeks of steady work to get it ready to put fire to it.  But I wanted to give it the best chance to come back to life and it paid off.  I changed the oil, filter, points, plugs, timing, valve adjustment, cleaned the carbs, etc. before I even tried to light it up.  I also cleaned and sealed the tank.  You do not want to run the crap in your tank into your carbs.  I have seen guys set up a temporary clean gas tank when they were ready to start it and the OEM tank was crap.  Congrats on your new project and keep us informed on how it goes.

[ChevelleSSLS6]

Tom has side covers off (shiny side down on the concrete floor! ) and some cans of general and harsh (carb) cleaners... I guess he'll try to shoot some in the carbs and hope it works.  It just seems safer to tear down the carbs and get new gaskets and o-rings, and clean out any crap that could have made its way in there.

*update* he just told me that he cleaned up the chrome and stuff on it.  I have no idea if it has oil in it, but hopefully he doesn't try starting it before making sure!  Tom did determine that he'll just buy a new tank.  I figure I'll adopt the old one, clean it up, and if it doesn't leak I could sell it.  Any ideas (besides ebay) as to where to get a replacement?

I'm personally a cafe/stock/mildly modified guy when it comes to sporty motorcycles with revvy engines like the CBs and my Kawasaki 650.  Motorcycles with heavier frames, low revving engines, and stuff like that (goldwing, harley, indian) is best left to cruisers in my opinion, as the sporting attitude of these bikes shouldn't be wasted.  It's tom's bike, and right now he just wants to get it cleaned up, and maybe running before he goes back.  Time will tell.  I suggested the service manual and such, but he seems to not be hearing me...

[ChevelleSSLS6]

update....
mod- please move this to the project section of the forum... this being a more technical section I started this thread in the wrong place.  Thanks! -matt

Tom has not yet to my knowledge created an account here.  Let's see... he borrowed some wrenches from the neighbor, probably mixed some of mine in with his...

He basically took the seat, air cleaner, and carbs off.  Then 'polished' the chrome (it looks sanded to me, as it's more dull, but any rust is gone), and scuffed up the paint on the engine and transmission, masked the bike (it looked kind of like a bright green michelin man motorcycle with all that masking tape) and shot some rattlecan, at about 6-8 inches away, and minimizing overspray (starting and stopping over metal).  It resulted in lots of drips and runs, and I told him to hold it a foot/foot and a half away and spray PAST the edge of what he's painting... but he doesn't listen.  He did rebuild the carbs, full of gunk as I told him they would be.  I am no Honda SOHC motorcycle expert, but I'm not stupid, either.  I grew up reading old auto/truck service manuals and hotrodding magazines and dragging old lawnmowers home from people's trash, not in front of the tv and video games like the brothers.

I think he changed the oil/filter, and added brake fluid, but I wonder if he has the slightest idea how to bleed brakes.  Let's hope he doesn't get it running and try going for a test ride!

Today as Tom will be shipping back to Cali to resume his work for the Navy as an aviation electrician tomorrow, he and dad were over putting it back together.  I told dad I re-oiled the KN filter, and he told me its not supposed to be oiled, and he never oiled it ever.  Looking at the bottom, it says KN and a little while later it says OIL TYPE.  He didn't say anything, rather changing the subject and wanting me to clean the garage (it's mostly the 750, and wrenches of mine he has scattered around.  I do have some out from wrenching on my Jeep though, so I'm not perfect, but it's a fricken garage, not a pebble beach concours winning rolls royce or anything).

So, I have retreated indoors and am waiting to go to work...

[steam-powered man]

not entirely sure what your skill level is, but not having a second gear would be a project-killer for me.  good luck, tho and keep us posted.
bp

[HondaMan]

A missing 2nd gear is usually either a bent shift fork or the tip of the groove broke off in the shift drum that moves the fork. On just one occasion, I have seen the shift fork's pin chipped (the pin follows the shifter drum groove), which mimiced a broken shift drum groove.

Any of the above requires splitting the cases to repair.

[ChevelleSSLS6]

It's my brothers... he would like to have $$ to have it fixed.  I'd have it cyrogenically treated for durability before reassembly.