Honda CB750 Restoration (Not sure of the year, I think '79 or '80)

[RideThis]

This bike belongs to dear old 'pa... The poor beast was sitting behind his shop exposed to the elements for 10+ years... My guess is closer to 15 years... He was gonna toss it but offered me a project... Hells yeah! So, I figure I'll update the progress here, I'm 100% going to need advice at some point!

This is with the ugly passenger seat back and storage rack removed.

The next day, moved it to its new home until scrapped or completed. Much better lighting in these pics.

I also managed to get 3 of 4 seized spark plugs out of the engine, and excessivly sprayed penetrating fluid into those cylinders... Unfortunately one plug snapped and is stuck in the head...

 

[RideThis]

So, a few days later I got a chance to work on it... And here's what happened...

Removed fuel tank and drained out 15 year old nasty fuel...

Tested my chrome cleaning skills, any advice on getting the fine pitting out?

My buddy Leo, applying leather treatment to the seat!

This healight housing is a total loss... Possibly the guage housing too...

Done draining out the junk...

Inside the tank after draining... Gross...

After varsol + hot water rinse...

Mixture of muriatic acid (2l) and full tank of hot water... (3 hour soak)

And once the acid bath was done, rinse with water followed by a rinse with gasoline... It's now filled to the cap with clean gasoline...

Also removed: rear wheel, swing arm, chain... And ensured that I could hand turn the engine before moving forward with this project... As I was hand turning, my stuck spark plug shot out! Still need to remove the seized threads though... Only the core shot out...

 

[RideThis]

Re: Honda CB750 Restoration (I think '79 or '80) Work In Progross

Advice needed:

The key wont turn in the ignition, no doubt all moving ignition parts are seized, anyone deal with this before?

Chrome cleaining, any way to remove the fine pitting? Wire wool + penetrating oil works well for the surface rust but need help with the deep pits...

That's all for now! Thanks for looking....

 

[polak]

Hi ,
have you tried this great forum for DOHC bikes ?
Guys there are great and they have a lot of experience with these bikes .
You can find manuals to download , suppliers , pictures , mods almost anything you can come across on these beautiful bikes.

http://www.cb750c.com/

 

[RideThis]

Cheers man! I'll check it out!

 

[RideThis]

So, I just got back from my buds house where this bike is being stored / worked on... I def need to learn about carburetors... Todays goal was to make her run... Fail... But had her cranking and trying to start! Cheated with some cleaner through the air box to try... Too early to be doing that... After today, I think the next step is airbox + carb removal...

First was to fix this busted fusible link type fuse... No one sells these apparently...

So I bought this instead...

To make this... I will make it cleaner later... This was just to get started...

Next, I still can't turn the ignition... That had to come out...

And this is the mess behind that giant headlight....

Got it out, going for an oil soak... More on this guy later...

No more light, no more guages, only wires...

Removed the air filter, found a rodent nest inside the air box... Super...

And took off the tops of the carbs and took a peek, here's what I saw...

I don't know what's good or bad... This looks ok to me, but I think the mess is in the lower half of the carbs... Right?...

 

[RideThis]

I was back on the biek briefly today...

1) I tried a few cheat methods off the net to get the bike to run without a proper carb cleaning... No dice... Carbs gotta come off...

2) Spark plug issues... No 4 plug, the one that snapped... The one where the core shot out when I was hand turning the engine... The one that now has seized threads in said cylinder... I tried to get that out with an extractor bit set from CT... Broke one bit that was too small for the job... And got the larger bit to bite hard but it won't turn...

That's all I did today... No pics... Today the bike won lol....

 

[Kokla]

The headlight encasing looks superb, what the nuts were you saying

 

[RideThis]

Soooooo, another evening with the CB750... Had a productive work session this time... With one downer... And still trying to figure out the busted spark plug removal...

So, like I said, carbs had to come out... To do that, needed to remove the battery housing...

(Right Side)

(Left Side)

Rear fender had to come off to get the battery housing out...

Still trying to ID this component, looks like an alarm to me...

Got the battery housing out!

Now the air box had to come out... Took me a while to figure out to take the carbs out after loosening the air box before trying to get the air box out...

So, carbs out...

Then the air box can be removed...

Now it looks like this...

Keeping in mind I don't know carbs very well, I opened up the bowels and took a look...

#1 Carb

#2 Carb

#3 Carb

#4 Carb

Still need to figure out the spark plug thread romoval for #4 Cyl...

And the downer, I had the choke cable out, and it was working well enough, but as I was working some ATF into the cable, I busted the plactic collar with my brute, monster like strength... So I ruined a good part... BOOO!

 

[skip]

On the bright side, none of the bolts holding the float bowl covers was seized! I end up replacing those with cap head screws normally.

 

[RideThis]

Delete

 

[RideThis]

On the bright side, none of the bolts holding the float bowl covers was seized! I end up replacing those with cap head screws normally.

This is true, + I figure the choke cable can't cost much more than $20 bucks... But I know OEM Honda can get rediculous...

 

[Cat13]

If you need help with vintage parts etc or how to handle a vintage bike (though it seems like you hardly need help) check out dotheton.com
Mostly vintage bike riders, I am sure someone has rebuilt a CB750. I am currently working on a CB360 myself and they have been extremely helpful in all aspects especially with the electrical issues I have had. As for good place to get parts call Glen at fsmotorcycle.com tell him Cat sent you his way. He has been very helpful in getting me parts and sometimes a better price when he know of it elsewhere. Also I know a few websites to check out for parts just msg me what you need.

 

[RideThis]

Cheers Cat!

 

[Cat13]

Cheers Cat!

Cheers back. Look like shes gonna be awesome when your done Keep posting pics!

 

[Gryphon]

Ahah....
I see the problem(s).
Makes me want to smack yer dad!
No offense - I bet you have felt the same once or twice in your life...
(But if he did give the bike to you, he's a good guy I s'pose.)
That spark-plug thing is nasty huh?
It's your biggest problem right now.
I have every size Keihin main jet, and a shop manual, if I can help you.
Good luck (it's noble work),
Regards

 

[Cat13]

Ahah....
I see the problem(s).
Makes me want to smack yer dad!
No offense - I bet you have felt the same once or twice in your life...
(But if he did give the bike to you, he's a good guy I s'pose.)
That spark-plug thing is nasty huh?
It's your biggest problem right now.
I have every size Keihin main jet, and a shop manual, if I can help you.
Good luck (it's noble work),
Regards

Keihin jets. I have a 360 I need to tune with the jets and am looking to get my hands on a variety of sizes close to stock sizes. Can find pilot and main but not slow jets do you know where I can find slow jets?

 

[RideThis]

And I wasn't going to do pics today... But why not...

Here's a pic the the bike's condition when I finished my last session on it... I would have put it with my last post but it didn't fit...

Today is a clean carbs day... Keep in mind I've never done this before, I'm working with the internet and mechanical aptitude...

So... I took the bowls off again, removed the pin that holds the float in place, then the jets... Also removed the gaskets... Then used the bowls as, well, as bowls to hold carb cleaner to allow the removed parts to soak... (not soaking the gasket or floats mind you...)

Notice #2 is in a tilted tupperware container... I broke a bolt (damn) so it's soaking in penetrating oil overnight... Extraction tomorrow hopefully...

A little closer...

And close up of said #2 bowl with the broken bolt in the penetrating fluid...

After setting up the carb cleaner soak... I removed the top ends of the carbs and cleaned things out with carb cleaner / wiping with a rag... Then did the same to the bottom end... Here's what the bottom end of the carbs look like...

Since everything on the internet is true, and someone said to boil carb parts in water to help break down deposits, then I figure I should boil some carb parts in water...

So I'm trying to learn the names of these carb parts here... So far I think what I have in this pic are: Front and centre are both jets, one main and one slow jet... Right of that is the float arm pin, and behind... Main nozzle? Anyone, anyone?

Here are the jets after boiling them and poking a small sewing needle through them...

Oh! And good news... I think I know why no fuel was getting into the carbs... The main fuel line from the tank goes into a vacuum activated diaphragm type device... Vacuum pulls down on a rubber diaphragm and allows fuel to flow...
(please correct me if I'm wrong someone, I'm just saying my thoughts)
So I took that bastard apart today and the diaphragm was sticking even with vacuum... So I cleaned it up and did a butchered bench test and seems ok now...

Next will be carb rebuilding, then head removal I think for the damn spark plug issue... Then after that, rebuild and start?

 

[Syphen]

Looking fantastic. Keep up the good work! Hope you get it running soon.

 

[skip]

So I'm trying to learn the names of these carb parts here... So far I think what I have in this pic are: Front and centre are both jets, one main and one slow jet... Right of that is the float arm pin, and behind... Main nozzle? Anyone, anyone?

Main, Pilot and needle jet holder.

Next will be carb rebuilding, then head removal I think for the damn spark plug issue... Then after that, rebuild and start

The start is always the moment of truth! Keep up the work, its looking good.