1982 CB750F...Better Devil

Re: 1982 CB750F Resto-mod. At least that's the current plan.

Got into work a couple hours early yesterday - now that I know my way around the tire changing machine, slinging on my own rubber was certainly a first. Big Red takes a bit of getting used to, but with the benefit of time on my hands the job's a good'un...

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Not sure what looks better, the new-look wheels or the startlingly red hydrant -

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Love me some new rubber. Definitely a wider rear tire than Rhonda, dig the look and looking forward to getting the wheels back on the bike. Hopefully got a long ride planned on Sunday but Saturdays plans are up in the air - need to do some work on Rhonda but also hoping to get this CB closer to her inspection. Carbs need a vacuum synch and brakes need bleeding, but hoping everything else will be ok enough to squeak through the safety exam. Then it's gloves-off time.

Avanté.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Got the wheels back on and started cleaning out the crud from the tank. On first inspection it looked clean as a whistle but there is in fact some old gas and varnish (no rust though) so got the old nemesis MEK in there overnight doing its thing. Plugged up the petcock hole with a rubber cork-type-thingy. Hoping it's held, otherwise, well, bad things are happening in the garage as I write.

Once the wheels were back on I actuated both front and rear brakes - the front is working just fine but the rear caliper seems to have seized completely on the disc - I can barely move the wheel. I'm thinking the best course of action is to crack the bleed valve, pry the caliper off and dismantle the thing for a proper clean. It looks a little toasty.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

MEK is used to add patches, or bond, damaged urethane rubber by breaking down the outer layer and making it tacky. A significant amount of MEK coming in contact with urethane rubber will completely dissolve it
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Once I’ve got breakfast down me I’ll find out one way or another...


Sent from my iPhone using DO THE TON
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Ha, it also melts ABS to make a slurry for repairs. Used it on the camper, going to do it again. Makes you dizzy if you forget the mask too.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Maritime said:
Makes you dizzy if you forget the mask too.
Click to expand...
If by dizzy you mean total cranial meltdown then yeah, dizzy :o
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Wheels, on -

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MEK, marinating -

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Rubber bung held up nicely, giving it another hour then draining the stuff. Damn that stuff does not fuck around in any way whatsoever.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Looking good. Good thing on that MEK.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Got the MEK out without any characteristic mishaps, so that was a first. Man that stuff makes quick work of varnish. Dumped 4 litres of gas in the tank to see if the petcock I salvaged was in decent shape - turns out it isn't, and I'm pretty sure these model petcocks aren't rebuildable. So on the hunt for a replacement - remember this being a ball ache with the other CB so hoping not for a repeat of that.

Pretty happy with the state of the tank's insides - apart from a bit of rust and Montreal's unhappiest wasp very little else came out.

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Re: 1982 CB750F Resto-mod. At least that's the current plan.

The return hole in the master cylinders on these bikes is small and can get blocked with crunge if the brake fluid is not changed regularly. You can use a high E guitar string to clean it out. This could be why your rear brake is seized but it could also be that the slave piston is seized. Can you remove the rear wheel, if so you can use a grease gun to move the piston out if it is seized.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Got the carbs vacuum synched and have to say the engine is humming along pretty sweetly. There's what sounds like a chain rattle from inside which I'm hoping some cam chain tensioning will address, but other than that I'm pretty chirpy.

Big mistake I made was not installing an in-line fuel filter - the carbs (which have only been given a rudimentary clean at this point) are leaking like a sieve. Gonna have to pull them again and give them a decent clean now that I've installed the filter and hope that'll do the job until I can get this thing through its safety exam.

Freed up the rear brake caliper a little but it's still clamping hard on the rotor - I think one of both of the pistons is sticking. Gonna pull the caliper, free out the pistons and give the thing a decent clean, see if that'll do it.

Managed to get the thing out into the alley last night for its maiden voyage. Best feeling ever, getting a non-starter to roll for the first time. No seat, tank lifted from the other CB...ugly as a blind cobbler's thumb but sounds pretty good, even if it was spraying 91 octane all over Montreal's finest.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Just in the final stages of reassembly on my '79 750F carbs. You're in for some fun! Inline filter is a must. There is a great manual in pdf form online to guide you through the rebuild - lots of photos and details. I think rev G is the latest. Still cleaning the inside of the tank on mine - been rolling it for a week with Evapo-rust in it. Begore that it sat with acetone for a couple weeks to remove the varnish left by over 15 year-old gas. Not really that much rust, however. It took a couple cans of spray carb cleaner and some guitar string in a pin vice to clear out all the varnish from carb passages and jets. The accelerator spray nozzles were real fun!
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

Man I love carbs. Working on them is one of my favourite parts of the (re)build - I've worked on the the Keihin carbs before on my other '81 CB750 so I've got an idea of what to expect. I closely followed Mike Nixon's really helpful booklet on how to clean and rebuild them which proved invaluable, and will follow it to a t again when I tear the bike down for a proper resto this winter. Right now just kinda bodging it to squeak the thing through its safety.

For de-rusting my tank I used Metal Rescue - just dump a few litres of that stuff in the tank and I was amazed at how well it worked. It needs to be warmed to work well. I knocked off all the big stuff with a length of coarse chain too. Good luck with the rest of your build mate, post a link to your build so I can have a look at what you're working on. Go the F's!
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

The Jimbonaut said:
Man I love carbs. Working on them is one of my favourite parts of the (re)build -
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Im with ya bud, Carbs are just little miracles of engineering and design.
To do what they do w nothing more than vacuum pressure is amazing.
The amount of education-math-R&D-trial and error over the generations all added up together, would probably be astounding.
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

trek97 said:
Im with ya bud, Carbs are just little miracles of engineering and design.
To do what they do w nothing more than vacuum pressure is amazing.
The amount of education-math-R&D-trial and error over the generations all added up together, would probably be astounding.
Click to expand...

Genius. I'm still wrapping my head around the minutiae of the things but the more I dig into them the more I'm fascinated. Much appreciation.

You wouldn't think it however if you saw the state of them right now - pissing octane all over my garage floor, arterial spray all over the ceiling. Looks like a mechanical nightmare version of The Shining. Need to get me some decent float bowl gaskets and clean up the float needles and jets again. Teach me for rushing and not installing an inline fuel filter. Lesson learned.

Finally got the rear brake caliper loose from the rotor - closer inspection revealed the rubber piston seals were all chewed up and preventing the pistons from moving. Tried blowing them out with compressed air but that got me absolutely nowhere, so hooked the caliper back up to the brake line and forced the pistons out by actuating the brake lever. One anyway, the other piston was jammed in there tight - took a wrassle with some pliers to get the thing out. Got a rebuild kit on order.

Need me some float bowl gaskets but don't want to spend the earth on them - any ideas?
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

The Jimbonaut said:
pissing octane all over my garage floor, arterial spray all over the ceiling. Looks like a mechanical nightmare version of The Shining.

Need me some float bowl gaskets but don't want to spend the earth on them - any ideas?
Click to expand...

Hahaha ;D

Yeah 4into1 is your best bet. My local Honda dealer has the complete o-ring set for your carbs...at $42.40 each. ::)
 
Re: 1982 CB750F Resto-mod. At least that's the current plan.

https://www.nbc.com/saturday-night-live/video/the-french-chef/n8667


Oh and carb kits....$46 for all four not bad compared to $42 a piece.
https://4into1.com/carburetor-rebuild-kit-set-of-4-honda-cb750f-super-sport-1980-1982/

If you're hoping the factory brass make sure to compare new w the originals to make sure new o-rings will properly fit the old stuff.

For mine, (400four) the float valve seats and the main jets were different diameters...had to go w the new parts so O-rings fit correctly.
 
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