Topic: '73 CB750 Restoration

[RHCP]

I picked this '73 CB750 (F I think?) up for free from family. It was my uncles prized motorcycle until he was in an unfortunate accident and is now unable to ride. I can't figure out exactly how long its been sitting, but I'm told its been about 30 years since it ran. It was well maintained when it ran, but once my uncle could no longer take care of it, the bike just sat. Someone in the fam did put a nice thick wax coat over the paint and the chrome, so the paint is in pretty good shape. The chrome, especially the front fender, needs some work. I do have the side panels too, but unfortunately I was too eager to start breaking it down. The engine doesn't turn over but, as you can see, I'm trying to free the cylinders up with Mystery Oil before I pull the motor for cleaning. We'll see how that works.

I think I'm going to keep it mostly stock but remove the sissy bar. Its badass as is.

(Note: The dates on the pictures aren't right. I took them today)

[RHCP]

Oh and I forgot to introduce myself. Off to a good start. I am 19 year old college kid living in central Massachusetts. I've been browsing the forum since I committed to the restoration. Being a college kid, funds are tight, while time (especial during the summer) is plentiful. I will be looking to put most of the money into re-chromeing and powder coating the frame. I also hope to rebuild the engine at some point (which may be necessary to just get it started) to really complete the project.

[Shane72]

Welcome from Iowa!

That looks like a nice start for a project bike.  Just FYI, it's a K bike if it's a 73--notwithstanding that someone put a 4-1 exhaust on it as some point.

All the best,

Shane

[RHCP]

Yeah your right. Should of just went on wikipedia real quick. I was seeing F's after certain numbers on the bike so I wasn't sure. But the VIN plate says it was made in '73 so your definitely right. Thanks for the heads up.

[RHCP]

So I have the carbs off (which was a pain in itself), but man are they gummed up. A 5 hour sit in simple green got most of the exterior dirt and oil of, but there was a ton of varnish built up. Carb dip and spray helped a lot with this, but I cannot get the float pins out. I don't want to break a post so I am being super careful.  The floats were seized to the pin and the pin seized to the posts, so the float was moving nowhere. When I hit them with the torc to try and pop the pins out with a finishing nail, I could see the varnish melting and bubbling. During the heating, the floats would move due to the varnish liquifying. However, as soon as the heat came off they would freeze up again. So back into the carb dip they go.......

[harisuluv]

Those float pins can get really nasty.  You are doing the right thing though, heat and solvents will help to loosen it up.  It might take a few attempts but usually you can get them out.  I would suggest getting a punch that is the correct size for the pin.  A nail will have less surface area at the point of contact, and will just be easier.  You can get one like this at sears, it is sized 3/32 and is pretty much a perfect fit.



I squirt some pb blaster or wd40 on it while I'm punching them out.  It can also help if you can get it going one way to turn it over and punch it the other way.  Then the wd40 will help to lube it and you can coax it out easier.  Also be aware that on some of the floats you will get up and down movement and at first you will say to yourself "it's free" and then try to get the pin out, but then it still won't come out.  This is because sometimes the pin is actually still attached to the float and they are moving in unison.  Anyways hope that helps, I just did a set with some serious lacquer problems.  Look familiar?

[RHCP]

Thanks for the tips and that picture is all too familiar. You are right about the float moving and the pin remaining seized. Once the pin was freed from the posts, I hit it with the torch again, melted the varnish that had the float seized to the pin, and quickly pulled it out with some pliers. Minimal damage to the pins and, more importantly, no broken posts. Next step: soda blast. I'll be sure to post some picture before I blast them though.

[harisuluv]

Cool!  As far as the minimal damage to the float pins if you have a dremel you can just put the pin in there and spin it along with some 600 grit sandpaper. It isn't coarse enough to take off significant metal but it will debur the ends where they might be a little misshaped from getting tapped on.

[d9canada]

Very cool project bike!  I just got a 73 CB750 to add to the herd.  I really encourage you to keep thing stock as you can. 

In only a couple years these bikes are going to double in value.  As you can see in my sig, I have a growing collection.  Here in western Canada, guys routinely advertise year-round to buy complete 750 SOHC or parts.  It's very tough to find any 70s or 80s Honda SOHC at all except for a few nice clean ones for big bucks.  And then comes the inevitable situation, you find a good bike but it's got no title..  But, every state in the US and province has differing regs but all have some sort of process for title recovery or reissue.

Re:carbs, I do mine with PineSol soak and soda blasting.  One thing, soda really promotes rust.  If you get it on steel parts like carb throttle pieces, do not rely on rinsing with water or even PineSol and then water.  Use a toothbrush and warm soapy water or a petroleum solvent if the situation allows. 

I also use electrolysis (posted a thing about doing this last year) which uses Arm & Hammer washing soda, very similar to baking soda, so again make sure you get the soda residue off the piece.

Oh, you may already have a good carb rebuild guide but here's one I think is good - http://www.salocal.com/sohc/tech/carb/carb.htm   also that site also has a good guide for fixing speedos and other helpful stuff.

I'll track your project thread, hope you have fun.  Please do PM if you want to discuss anything.

[Denotslaer]

Glad you are aware of the post issues with these carbs ! But also keep in mind that when you are re installing ... they have a tendency to become even weaker . I would highly suggest getting some new floats and pins ; 30 year old pot metal is weak , you don't want this to happen ......







DENO

[d9canada]

Another thing you can do on carbs, if you find the white oxide growing on things, soak them in white vinegar.  Vinegar will not damage metal or plastic if you soak it for a few days, but it eats the oxide.  It's not a perfect fix, but it's another thing that does work in some situations.

[RHCP]

So I've been really busy with work and school, so much so that I've neglected to get much done besides clean the carbs fully and pull the bike apart. I do have some pictures of the make-shift rig I worked up a while back using a swing set to get the front end off and hold the bike together. It also acted as protection from rain and the like while I was pulling it apart. Probably should have used a stand or a lift, but we use what we have. I'll post some pics. Sorry in advance about the lighting.








Anyway, I have since taken everything off and I am down to the bare frame (no pics unfortunately). My biggest problem now is the seized engine. There was no way I was going to get it to turn while on the bike. Even with ATF and acetone, I still can't get anywhere. I pulled the points cover and put a 23 mm ratchet on there. The shaft (?) now spins but the cam and the timing chain are still not budging. Did I break something? I didn't force it and everything was smooth. I had to use a little persuasion (all muscle and regular ratchet, no cheater bar) and I didn't even pull that hard. This engine is really starting to get at me.

[Vinhead1957]

I would say you did ! That is the delicate end of the crank. That motor needs disassembly. If It is that frozen. Pull the motor pull the head and really see how bad it is