New project, a bit less ambitious- 1975 CB750F Blue Angel

NoahAbs

New Member
Hey guys,

So after a massive FAIL with my RD250 project, where I got a bit too ambitious with the angle grinder and ended up with a bike with no shock mounts (please don't ask, I am truly stupid, the bike cost 100 bucks, chalk it up to a learning experience) I got a new project.

Kinda boring after a nichey bike like an RD, but I found a pretty decent CB750F for 500 bucks. I waffled a bit, but the Kerker exaust on the thing is worth a few hundred alone, and though it isn't running, the owner says it was just a few months back, and the whole bike looks pretty clean, unlike the last rusty beast I had. The PO said the battery is just juiced and that the shims on the exhaust are crappy, but he included new shims and a bunch of other parts too. Here 'tis.

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Since the bike should be able to run with not too much work, my plan isn't to do a full tear down...yet. The frame paint is pretty solid, so I am just going to shine everything up, and do all the mods I can without taking the engine out...mostly cause I don't trust myself to not super-F it again. I am still going to do a bunch of work, but I don't plan on polishing or painting the engine too much, I believe in a bit of "patina" and love how the wrenchmonkees guys' bikes look like theyve all been through world war 3.

The tank on the bike is off a different 750F, but is clean and the paint has inspired me to stay with a blue theme, which I don't see a lot of on the site. I think I am going to try and do something like the Navy Blue Angels color scheme, mostly blue with some white and yellow/gold striping.

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Ok guys, guide me, what are your thoughts? Anyone have experience with exhaust not mounting well, causing the bike to run crappy (I am thinking thats where this is going...) Suggestions?
 
Nice find. My first piece of advice is to not be timid just because of what happened with the other bike. Learn from your mistakes, but dont let your mistakes keep you from being ambitious. Second, get a clymers of haynes manual for this bike. In my cb350 clymers the first like 20 pages is all about testing for spark, fuel and air. If I had a bike which I thought had a chance of running without digging into the motor, this is where I would start.
 
The CB looks like a good place to start! 8)

Don't beat yourself up too much on the RD Project! Hang on to it! It's repairable!! It'll make a nice "compliment" to the CB! :D

You might want a smaller bike sometmes for blasting around the city! There's something about a 2 stroke too! Very anti-establishment! :D :D

Goot luck with both bikes! ;D
 
Thanks guys. Yeah, I probably "shouldn't" have bought the bike ,but the deal was just too good to pass up.

So I have run into my first issue. The PO said the exhaust shims were bad, and even a quick glance showed he was right, they were all out of wack and poorly aligned. So I was trying to remove the exhaust to put in new shims, get the rust off, and then wrap the headers. One of the bolts that holds the finned clamp off is totally rounded out, and in a super crappy position for getting any tool in to free it. Anyone have a trick for that?

Also, what do people suggest for getting the rust off the pipes? I don't want to scratch the ceramic coat too much. If I do, I have some semi-gloss black engine enamel I guess I could just repaint them.

Took the seat and rear light and signals off, definitely can see it better in my minds eye. The stock headlight arm is a BEAST, totally overbuilt and all of the wires into the headlight are threaded through it a million times. Cleaning up the front of the bike will go a long way cause right now its super busy.
 
try posting up a pic with the exhaust stud issue, Im having a hard time visualizing exactly whats going on. As for the rust on the headers, youre gonna have to scratch some of the surrounding area to be able to remove the rust. Youre going to have to repaint them. That being said, do not use engine enamel. It is rated for 500°F, while exhaust enamel is rated for something like 1200°F. The engine enamel may work, but why risk it?
 
Don't fret the RD. We all start with a clunker as a first project. I bought a '81 CX500 for $200 running. Spent $400 to get a title and about $300 in paint a parts to do a cafeish project. Bombed it by trying to rebuild and synchronize the carbs myself ending up ruining them. Sold the whole thing for $600.
 
Ok, a little more work done. Got the stock air box out, that thing is a beast, I think I will put a handle on it and use it as my lunch box, man its big. Also got the stock headlight/turn signal bracket off, which is also huge, with about 4 more bars than it needs. Weird.

The bolt on the header flange is still not coming off. Here are some pictures, as requested. Its just at such an awkward angle I can't figure out how to get it out since the trusty ol socket wrench is just sliding around on it like two chicks mud wrestling (that was my ridiculous Carpy analogy for the day...)

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You can see it on the right side, access to it is blocked by the frame, the other header, and the fact that its a tiny freakin bolt recessed into the flangey thang.

I know there is probably some simple solution I can't think of. Guess it shows that I'm simpler than simple.

Also, with the air box off, some pods on the way, and hopefully eventually getting the Kerker off, painted, possibly wrapped, and back on, how am I going to have to jet this beast? I am not even touching the carbs until I spend a good 10 hours reading everything I can get my hands on about how exactly they work, how to re jet, etc. I have done verrrry minor adjustments to other bikes before, but I have never done anything like this, and don't want to ruin the bike before I get started. Anyone have some concept of pod filters+kerker 4 into 1 for jetting? Thanks a ton guys.

I will get a pic up once the first parts I ordered start rolling in. Already it has a way better stance, and I can see where its going. It's like David waiting to get cut out of the block of granite. Well, if instead of Michelangelo as the artist it was, I dunno, R. Crumb or somebody.
 
so there are these sockets that are meant for rounded off nuts/bolt heads. They have clockwise spiraling teeth so that when you turn it to the left they grab the nut/bolt head. You should be able to find these at any autoparts store or home improvement store. As for the carbs I think its not a horrible idea to just start at stock and go from there. Jets are cheap, and any rebuild kit will already come with stock jets.
 
Everything I've read about the CB750's says they run like crap without the airbox. The saving grace with the carbs though is you can remove the float bowls without pulling the carb rack off, so jetting changes are (fairly) easy.

As for that exhaust stud, if you can get a smaller socket on there and try to hammer it on, you might be in luck. Otherwise, do you have a welder? You could weld a bolt onto the stud and try to unscrew it. The heat from the welding will help the stud loosen up as well.

Good luck with it ;)
 
Stuck bolt? No worries.

Buy a hacksaw blade and use it to cut a fairly deep slot in the head of the bolt. Then, after soaking the thread with penetrating lubricant (eg: WD40), use the blade or a screwdriver to undo the thing. Easy...in theory. I found it out after the PO of my GS sprayed the engine black without masking bolts and the like. Damn.

As for the airbox, everything is going to run crappily if you mod the intake and don't change the jetting or needle height. Seriously, once you sync the carbs and jet them properly there isn't any reason that it shouldn't run well with pods/stacks/bits of poly pipe. Airboxes are only beneficial if well designed. This usually means tapered inlets, big end closest to box. That makes air denser, a good thing. The box will ideally be divided by the filter media, with the carbs being on the side the air inlet isn't. This (again) makes for stiller, denser air. After all that, the carbs will ideally have stacks on them for smoothing the airflow. The height of the stack/s will give better characteristics at different rpm, longer being better for high rpm work and vice versa.

Stay tuned for more half-assed, hard-learnt tuning tutorials ;D

Cheers man, killer project - boingk

PS: Yellow frame w/blue bodywork & yellow stripes. Or vice versa.
 
Noah,

Hold on a minute. I have a CB750F as well and similar problems. First, the smaller socket idea might just work, sometimes shocking the not will loosen it up. If you haven't tried it, PB Blaster is a good penetrating lube, stinks like hell, but works pretty good. Did you also try a little heat, that works sometimes too.

Don't cut a slot in the stud and try to remove the stud and the nut at the same time, you'll lose that battle!!

If all else fails get a Dremel tool with a cutoff wheel and cut into the nut being careful not to score the threads on the stud. Cut as close to parallel to the stud and when you get more than halfway through, use a small chisel to crack the nut. You just have to expand it a little and it will come right off.

Let me know if you need pictures.

Scott
 
So, after taking some suggestions into account, heres the ongoing saga of the Rounded Nut...

There's no way a hacksaw blade would fit in that spot, and further, its a nut, so there is no head to make a slot on.

I went to Sears and bought this:

http://www.sears.com/shc/s/p_10153_12605_00952160000P?keyword=craftsman+bolt+out

Had the best rating I could find (that vs. GripTite sockets) and it seemed like it would do the trick. Basically the socket version of a stripped screw remover.

So I tried it, and it didn't work. At all. Just cut some more of the nut off. Soon its going to be just a very thick, threaded washer.

I think I am going to try the "whack it with a punch and hammer" route to see if I can at least move it a tiny bit. Then its Dremel time. I need to buy one eventually anyway. (Since everyone on this forum is so handy with one I think they could use it for open heart surgery.) Very frustrating. 1 nut out of 8 is messed up and the entire exhaust will not budge until its out.

Wish I had some more interesting news, but sadly, no. All I really want to sort before trying to get it started again is the exahust, carbs, and the new battery (in the mail) so fun stuff is soon to come, just have to square away this damned nut.

Nuts.
 
NoahAbs said:
...and further, its a nut...
Hahaha! ;D Nice, good to see I was paying attention. Sorry, mate.

If a nifty tool like that Bolt-Out didn't work I'd definitely try the punch-n-hammer routine before the dremel. The dremel will be a good investment, though. Must be pretty darn well stuck on there...geez...

Don't get disheartened! - boingk
 
That's a pretty nice F for a restore. I'd have a real hard time choppin, hackin', and hammering the shit out of her! Still looks like the stock tire on the front??? Get 'er running, and lookin nice. Sell her for a profit to an F lover. Take a portion of the money and by another bike that deserves to be hammered, then take the rest of the money and buy parts, and tools.
 
Ok, I was finally able to jimmy the shim out of the exhaust flange that has the stuck nut. That gave me enough room to get the exhaust out, so at least that is done. I am going to steel wool off all the rust (and probably some of the paint) and then repaint with flat black exhaust paint. Will probably wrap the headers with black wrap while im at it, I am trying to do as much work on each part I take off as I can before putting her back together.

That being said, the nut is still rounded and stuck and the flange is still on the engine block. I want to paint the flanges while im at it, so I definitely need to get it off. Has anyone ever used a nut splitter?

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_34573_34573

I guess it slips over the bad nut, and then you tighten it down with a ratchet, and the sharp end breaks the nut. Again, I think I am going to run into a clearance issue here where the splitter wont fit in the small space available within the flange.

Anyone ever just heat a nut up a bunch and then pound a smaller sized ratchet head onto it?

Parts should be getting here early this week, new pics should be up midweek, Friday at the latest.
 
NoahAbs said:
Anyone ever just heat a nut up a bunch and then pound a smaller sized ratchet head onto it?

Heat will definitely help.

Do you have enough room to get a pair of Vise Grips on the stud? If so, heat the stud with propane, grip it and unscrew. Or use a flat punch and give the stud a few solid hits, then unscrew.
 
Yeah I think heat is going to be the way to go. The is almost no room at all to use any tool other than a deep socket on the nut. It is recessed in the exhaust flange, and is really tough to get to. It's even a tough angle to get a good knock on it with a punch. What would people suggest for cheap, relatively safe, heat? Also, anyone have experience with a nut splitter? I might also just get a dremel.

Got some of the parts in, heres the rundown (pics soon):

-New headlight brackets, got em on ebay, and they suuuuck. Really cheap looking, not a fan, dont even bolt onto the fork especially well. I really like the way the WrenchMonkees guys use headlights that bolt on the bottom to the lower triple tree. During the winter, during the more extended teardown I will probably bring the headlight to a welder and get a bracket welded on for a light like that. It's a big of a Harley styling touch, but it is very minimalist, less clutter on the forks...

-Got pod filters from the same seller and actually like the quality, but they don't fit. They are being cool and letting me do an exchange. Should be a week or two.

-And i need less clutter, cause I put clip ons I got from PartsNMore on the beast, and they look awesome! 50 bucks shipped, nice angle, not too long, perfect. Got a nice pair of vintage white grips on them too and I'm really happy with the look. I might have to go with some different hand controls though, not a ton of space on the bars.

-Took the seat off, took off the rear cowl and put it back on. Looks fine for now. Once its running and I'm happy with it mechanically I will get a bumpstop seat and send the seat, tank, and side covers for paint.

-Screwed up the headlight, dropped it while removing it and it broke, plus I tried to strip the paint off the bucket without thinking that it is plastic (unlike my RD or CB350) and it got eaten up by ol Aircraft.

-Anyone have experience wiring a CB750F very simply? Ideally I am going to lose the big gauges and idiot lights and all the hand controls except for a simple turn signal switch and horn button on the clutch side. I am going to use a turn-key ignition from cycleexchange (http://www.cyclexchange.net/Elec%20System%20Comp%20Page.htm about halfway down the page) I've always felt a little lame pushing a button to start a bike, but don't always want to kick it to death.

Pics tomorrow. Still very rough, but I am beginning to feel the soul shining through.
 
careful heating the nut up then pounding on it as youre likely to bend the stud since the heat will transfer to it as well.
 
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