Author Topic: 1981 Honda CB750C Custom  (Read 20931 times)

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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #25 on: August 23, 2008, 12:21:09 AM »
One last picture



The bike is 99% done.  The brakes get done tomorrow morning.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #26 on: August 26, 2008, 12:01:25 AM »
HELP!!    :bawl:


Both bleeder valves (regular screw-in types) on the front brake calipers are rusted, busted, and broken.  One of them is mostly intact but the previous owner used a freaking wood screw to close it.  The rusty screw broke off at the top of the bleeder valve.  The other bleeder valve is rusted and mostly crushed from where I tried to loosen it using a pair of vise grips.

Do gas torches work?  I can get one for ten bucks.  I don't want to damage the caliper or the piston since OEM calipers are $300 each.  I could probably replace them with generic brake calipers since they're mounted to brackets that bolt to the front forks. 

I was considering using a high-wattage soldering iron to do spot-heating because it could fit inside the bleeder valve (well, the one that doesn't have a screw stuck in it).  I'm concerned it wouldn't be hot enough to loosen the valve.

I could just drill out the bleeder valve, but I don't know where to find over-sized bleeder valves for this bike.
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Offline RobJohnson

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Re: 1981 Honda CB750C Custom
« Reply #27 on: August 26, 2008, 12:10:09 AM »
Okay, I'm glad I took a picture of that because I just dropped the whole thing on the floor. :rofl:

 :-)

Offline LC EFA

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Re: 1981 Honda CB750C Custom
« Reply #28 on: August 26, 2008, 10:27:27 PM »
HELP!!    :bawl:


Both bleeder valves (regular screw-in types) on the front brake calipers are rusted, busted, and broken.  One of them is mostly intact but the previous owner used a freaking wood screw to close it.  The rusty screw broke off at the top of the bleeder valve.  The other bleeder valve is rusted and mostly crushed from where I tried to loosen it using a pair of vise grips.

Do gas torches work?  I can get one for ten bucks.  I don't want to damage the caliper or the piston since OEM calipers are $300 each.  I could probably replace them with generic brake calipers since they're mounted to brackets that bolt to the front forks. 

I was considering using a high-wattage soldering iron to do spot-heating because it could fit inside the bleeder valve (well, the one that doesn't have a screw stuck in it).  I'm concerned it wouldn't be hot enough to loosen the valve.

I could just drill out the bleeder valve, but I don't know where to find over-sized bleeder valves for this bike.

All it really needs it to be hot enough to help get whatever is gluing it shut to soften , I use a combination of a MAPP gas or acetylene torch and a spray lubricant / dewatering product like CRC / WD40 to loosen bolts and the like that are stuck. Ideally the heat softens ,then WD40 assists in washing out the goop that has locked the thread on.

Never know, the previous owner might have used loctite on the thing as well.

Giving them a light tap can help as well. Clearly the smaller the thread and fittings the lighter you tap it.

The one with the screw in it will present a problem and is probably best if you just replace the valve if that's possible, I'd have to think on how to actually remove the screw without doing more damage than is easily repairable.


Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #29 on: September 14, 2008, 03:18:49 PM »
Some progress, none of it good.  Tried to remove the rusted bleeder valve with a screw extractor.  The extractor broke off into the bleeder hole.  Got the caliper seperated into two parts and found that the piston is welded in place and will not come out.  More rust.  So I'm looking at $200 to replace one upper caliper, piston, and gasket (if they're even available) or I can try to find something that will bolt into place from another bike.  And I still haven't touched the brakes on the other side of the wheel.  Those are in even worse shape.

Old vehicles are fun.  Yay.  :p
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #30 on: September 14, 2008, 10:39:22 PM »
I can't do anything with them, they're going to have to be thrown away.  The pistons are fused to the caliper.  And it's not surface rust... they look rotten.  No wonder I couldn't bleed them.

I found a place that has a pair for $100.  Good deal, but I need to know if they can be rebuilt.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #31 on: September 14, 2008, 10:40:20 PM »
Found a single caliper (left side) for $25 on ebay, but it doesn't have a 'Buy Now' option.  I hate eBay.  With my luck, it would be $75 before the bidding was done.
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Offline Wineslob

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Re: 1981 Honda CB750C Custom
« Reply #32 on: September 15, 2008, 02:50:31 PM »
Well, I was going to scream.............STOP!!!! but..............too late. A machine shop could have removed the bleeders or re-machined the bleeds to fit a larger size. The frozen pistons can also be removed, but probably destroyed in the process. I'm not sure if a rebuild kit would contain pistons.
You might want to find out what models shared the same calipers, might help with the search. Also, if you have a "U-Pull It" wrecking yard you could find what you need.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #33 on: September 15, 2008, 05:45:49 PM »
You might want to find out what models shared the same calipers, might help with the search. Also, if you have a "U-Pull It" wrecking yard you could find what you need.

I scoured the internets... the only thing I've seen that fits are calipers from the same series bike over a two-year period.  Pretty slim pickings. 

Someone has to have done a brake upgrade on a CB-series bike, but I haven't found one. 
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #34 on: September 15, 2008, 08:10:24 PM »
SOLD!

http://cgi.ebay.com/ebaymotors/1980-Honda-CB750-F-Used-Front-Brake-Calipers_W0QQcmdZViewItemQQcategoryZ35581QQihZ006QQitemZ160167405535QQtcZphoto

The bleeder valves look relatively new and clean.  At least they don't have a wood screw jammed into it to keep it closed.  :whatever:
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #35 on: September 18, 2008, 05:26:05 PM »
Wooo!! :hyper:

Finally got the carbs set up right.  Had to re-set the pilot screws to the correct position (3 turns from seat) and correct the idle screw.  Now I don't get that funky high-RPM racing after giving it a little gas.  Smooth, even throttle... runs like a dream.

Now all I need are brakes and I can go for a  ride.
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Offline Flame

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Re: 1981 Honda CB750C Custom
« Reply #36 on: September 19, 2008, 08:15:13 AM »
Now all I need are brakes and I can go for a  ride.


Yep, brakes are a good thing!

Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #37 on: September 20, 2008, 10:14:12 PM »
Anyone got any advice on growing a second wrist or an extra set of knuckles?  I missed one of the pilot screws on the carburetor and can NOT get my hand in there.

I obviously need more tools.  :p

Yep, brakes are a good thing!

They got mailed yesterday.  Hoping they'll be here by Wednesday.
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Offline Wineslob

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Re: 1981 Honda CB750C Custom
« Reply #38 on: September 23, 2008, 02:37:21 PM »
Anyone got any advice on growing a second wrist or an extra set of knuckles?  I missed one of the pilot screws on the carburetor and can NOT get my hand in there.
I obviously need more tools.  :p

Yep, brakes are a good thing!

They got mailed yesterday.  Hoping they'll be here by Wednesday.

Would removing the airbox help??
“The national budget must be balanced. The public debt must be reduced; the arrogance of the authorities must be moderated and controlled. Payments to foreign governments must be reduced, if the nation doesn't want to go bankrupt. People must again learn to work, instead of living on public assistance.”

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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #39 on: September 23, 2008, 05:26:01 PM »
Would removing the airbox help??

The pilot screws sit in front of the carburetor up against the motor -- the airbox is on the other side.  I can't get my figers past the first carb to get to the second one.  I think I can use one of those midget screwdrivers (short and fat) tomorrow.  Shouldn't be too much of a problem.

Did I mention UPS ground is slow as dirt?  My brakes have been sitting in Portland, OR since Friday.
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Offline lizard

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Re: 1981 Honda CB750C Custom
« Reply #40 on: September 29, 2008, 02:56:27 AM »
Nice bike.  I just (about 3 months ago)  gave away a matching pair of 1975 Honda 360 CBTs.   One red and one green.  I had ridden one some off and on for a few years and the other was just taking up space in the pack house, the red one was relegated there also after buying and getting my old Harley like I wanted it.
I may have been crazy for giving them away but, the dude (close friend) is already half way through the red one restoring it...says he is going to do them both for him and his wife to use.

I ended up with the Hondas after the elderly man that owned both broke his hip falling turning into his driveway.  His wife sold them both to me for a song.  I got my money's worth out of them with use and wanted to see good use come of these 2 stock bikes and nobody wanted them for that....so when I found someone interested in restoring them (they were actually in extremely good shape)...I gave him a deal he could not refuse.   :cheersmate:

Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #41 on: September 29, 2008, 06:34:29 PM »
The CB is a nice bike, but I don't think you could talk me into buying a 350. 

The new brake calipers showed up today.  :)
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #42 on: September 29, 2008, 09:40:31 PM »
I'm still dealing with electrical issues.  Namely, where the hell does that ONE green wire go?  I made a list of all the green wires last night... time to play the Elimination Game. 

Futzed with the rear brake drum over the weekend, so that is good to go.  Also need a new clutch cable.  I hope I don't need a new clutch to go with it. 
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Offline lizard

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Re: 1981 Honda CB750C Custom
« Reply #43 on: September 30, 2008, 08:46:24 AM »
If you are ever in NC and need parts for that bike, a town near us has a Honda dealership has a two story warehouse full of wrecks and parts bikes.  I had an old old Honda dirt bike that I needed a front rim and brake assembly for, well after half the morning crawling around the warehouse, jackpot - 2 just like mine with loads of good parts. 

It is Currie Chainsaw (weird name for a Honda Dealer) in Lumberton NC.  They are pretty weird about letting people go in there if they don't know you but, they will go and look for what you need and get back to you.

Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #44 on: September 30, 2008, 05:28:30 PM »
I'll check them out if I need something.  Thanks.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #45 on: October 02, 2008, 09:37:25 AM »
After much research, I found that the extra green wire is exactly that... an extra wire.  It's there as a ground for circuit testing or for accessories (some models came with a radio).  Which means there is something else causing my blinkers to act funny.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #46 on: October 02, 2008, 10:05:37 AM »
One side doesn't blink... turn it on, and it stays on.  I don't remember if the running lights are working either.  I know the tail light doesn't work.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #47 on: October 02, 2008, 10:06:20 AM »
And the piston on one of these new calipers seems to be stuck.  Damn.
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #48 on: October 08, 2008, 08:27:49 PM »
Pff.. not a biggie, you were going to take apart and clean 20+ year old calipers anyways right...  :uhsure:

Stop readin' my mind.   :lmao:

I'm online right now looking for a schrader valve with a metric thread on it that I can screw into one of the bolt holes.  I was going to try to use an air compressor to push the piston out.  Beyond that, I'm not really sure what I can do. 
« Last Edit: October 08, 2008, 08:33:55 PM by Chris »
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Offline Chris

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Re: 1981 Honda CB750C Custom
« Reply #49 on: October 11, 2008, 09:33:32 PM »
Woohoo!   :cheersmate:

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