Topic: Mac's 1972 CB 750k Build

[mac_48]

Hey Guys,  this will be a slow build but I thought I should keep a record cause I really regretted not doing it for my last project.  Anyways, I picked up a '72 CB 750k off of craigslist because it was the right deal at the right time.  It hasn't been registered since 1990 and was last started up in 2007.  It doesn't seem to shift right, the throttle won't twist, it squeaks when it's rolled, it needs new spokes, rims need to be either painted or replaced and much more.  But for $660 I feel like I got a decent price.  Enough of me yammering though; here are some pics:

Day it got home:



Side fairings and backrest removed:



Fairing Removed:

[mac_48]

That shed a ton of weight and made the bike actually manageable.  I was worried after I got the bike that it was going to be a huge flying brick but now it doesn't seem that bad.  I'll be shaving some weight as the build moves forward but right now I just need to focus on starting it.  I will be trying to find the oil drain plugs as well as how to drain the gas today to replace them and see if it starts up.  The engine seems a bit sticky but it is free so that will probably clear up after running for a bit.  It also needs a new battery so idk if I can just kick start it or if I need a new battery too.  The fact that the throttle won't freely twist also bugs me but I'll work on fixing that later.  I'm not planing on riding it yet, just checking to see if it can still run after sitting for so long.

[seanbarney41]

Probably won't run any good, if at all, if your sticky throttle is caused by gummed up carbs.  The carb's float bowls will come off with a gentle pry on the retaining wire and you can take a peek inside...chances are your gonna be clearing a big, clear spot on your favorite workbench and then heading out for carb cleaner...and yes. you will need some sort of battery to try and start it...jumpered car battery is ok, just don't attach the bike to a running car...

[mac_48]

Well I went to take off the tank and realized that there was fuel in it.  I don't know how I missed that, I think that it was all the excitement about the bike...so anyways I drained it and it took a while, so I started thinking about the throttle and thought about rebuilding the carbs while I was at it and on and on... well at least I was planning on starting it lol... I did take out the spark plugs and kicked it to see how smooth it cycled and it was like butter so that is good.  I got the carbs off tonight as well which was cool, but I ran out of time so I wasn't able to make it much farther than that.  Now I just need to decide which carb rebuild kit to go with....

[Garystratos201]

Sticky throttle might be the cables. Try some wd40 down ther cable housings. Might help.......Gary

[Killer Canary]

It' astounding how many old bikes had barn doors bolted to them. At this rate, the world will be cleaned out of buckets and rings in no time

[mac_48]

haha, yea they are in the oddest places too    I checked the throttle after I took out the carbs and it rotated really smoothly so I figure that they good.  I might replace them later after I check for rust though.  One thing I noticed was a snapped bolt head when I was taking off the carbs and linkage. (red) Should I use an extractor to get it out and replace it?  And does someone have a closeup pic of the throttle cable assembly on the linkage so that I can figure out what way that spring that wraps around the linkage is supposed to go? (green)

[Tews19]

How did I miss this one! Subscribed!

[mac_48]

Well, I haven't done much to the bike so far.  I did change the oil and while I was at it dropped the oil pan and cleaned it up.  There was some sand like gunk in it so I am not sure what I am to make of that.  Unfortunately I forgot to grab some pics.  I am thinking about doing an engine rebuild later, but right now I am just concerned about seeing if it can even run.

I also took off the exhaust and noticed a black powder that poured out of it I'll try to grab a pic of it when I can but it was weird.  The PO said that this was kerker exhaust so I don't know if that is relevant.  I've been thinking about going with shorty exhaust anyways so I might either chop down the current muffler or get a new one.  I also see what looks like chrome so I'm going to use some paint stripper to check out what's under that flat black paint.

so the short term goals include:
-Strip exhaust paint
-rebuild & reinstall carbs
-electrolytic rust removal in tank
-strip coil wire end and reattach spark plug boot on one of the cylinders
-change spark plugs

some things I am not sure which direction I am going to go on: 
-I might run dual disks and emulators on the stock forks or replace with some sport bike forks
-The rims need to either be cleaned and pc'd or replaced (not sure about the rust level and I do want black rims with stainless spokes anyways)
-Cable replacement (it feels smooth but takes slightly more effort than newer bikes I've ridden)

There is a huge amount of stuff that is running though my head that is way down the road like what torque wrench to buy for the engine rebuild.  It's hard to focus on a single thing to fix for me because as soon as I start to do something I find something else I want to do.  That's why I have decided the first thing I need to do is to focus on starting the bike.  Sorry for all the babble, it's just hard to pin down all my thoughts 

[dhall57]

Mac you would be amazed how many of these 40 year old sohc4 bikes that have set for years will start up and run good after some TLC. Don't think just because its a old bike that a engine rebuild is mandatory. Most the time its not. Bike looks 100% better minus the fairing and back rest.
Good deal at $660. Good luck with it and keeps us posted. I have a 750KO and a 750K6 and love both of them. Im sure you will yours to.

dhall

[Shane72]

Nice find!

I'd never seen the lower fairings of this design before--pretty neat.

Keep at it, you'll get it.  I love my '72, bought it last Fall and spent the Winter doing all the necessary rehabbing.  It ran when I got it, but only just.  Leaky tank, dirty carbs, cables and levers past useable, master cylinder and caliper in need of rebuilds, tires shot, suspension sacked, lighting sketchy, rubber lines, gaskets and hoses hosed, petcock junk, battery flat, and a few other projects I can't remember.

Loads of fun now, super glad I stuck to it--betting you will too!

When I ride the 40-year old K-bike to the local bike nights here, it stops more people to look at it and talk than most bikes do.  Seems these things are irresistible.

All the best,

Shane

[mac_48]

dhall57 - Thanks for the tip.  I am sort of on the edge of whether or not I want to rebuild because I noticed some fresh oil on the engine when I was looking at it after the oil change.  It would make it so that I knew the status of the engine and give me the opportunity to change out the studs with HD ones.  I'm still not sure what I am going to do about that yet tho. I completely agree about the fairing too, that extra stuff made it a lot heavier.

Shane72 - Thanks! I definitely have a lot of work to do on this bike but it really is half the fun of these old bikes.  I am not looking forward to fix the rats nest in the headlight bucket cause it was rewired to a plug that hooks up to the fairing. Plus I need to be on the lookout for all the hardware and besel to mount the headlight in the bucket.  All I have is the light and the bucket.

Here are the pic's I mentioned earlier:

Wheel rust, to PC or replace...


Stuff that came out of my muffler:

[bjbuchanan]

The black stuff coming out of that exhaust is rust. Maybe a rotted baffle or something like packing.

Keep up the good work the bike is bice

[Duanob]

Here are the pic's I mentioned earlier:

Wheel rust, to PC or replace...

Hey Mac welcome from another Seattlite. As far as the rust you can try steel wool 0000 and see if the pitting isn't too bad. If it is then you might be able to find a front wheel on CL, EBAY, or even Bent Bike for not much money. How is the rear wheel? All in all rust sucks. If its just surface rust then you can deal with it but if its deep then you just end up replacing or painting parts. My 550 came from Idaho and one of the things that made me buy it was my chrome was in exceptional shape. Good luck.

edit to add:
Just saw this today. I don't know what your plans are with the bike but if you're restoring it these might be the ticket: Nice original 4x4 pipes. New they are around $1200

http://seattle.craigslist.org/see/mcy/3347018640.html

[mac_48]

Thanks for the tip, I'll see if that gets the rust situation under control.  I am thinking about eventually going for a brat style build so I am not sure what I am going to do with the exhaust yet.  I sort of want to run a gloss black shorty reverse cone megaphone on it but idk if I am going to go down that road or not (something like this: http://coneeng.com/pdf/motorcycle/MC%20finsihed%20Mufflers%20PDF.pdf).  Some of the black paint has been scraped off the exhaust and it seems like it might be chrome underneath it all.  That pic showed the only really bad part of both rims, the rest are just covered in specs of surface rust so hopefully that steel wool will fix that.  Black PC  rims and ss spokes are growing on me and I have been toying with the idea of doing it myself.