Author Topic: 1970 CB750 Rebuild (Actually a K4 based on the VIN) (Read 8062 times)

Findlater · « **on:** October 28, 2008, 09:19:14 AM »

1970 CB750 Rebuild Day One.

Hey all this is the beginning for me and Ive never attempted it like so many people here. I don't even know what the bowl of a carb means for example of my newbie-ish-ness.

SO Ive done alot of work on cars so Im pretty sure I'll be able to handle most things but as a motorcycle Im sure there is a lot of other things Im going to look at and say to myself "What the f*@k is that?!"

This is the first of far more pictures to come, the first day working on the bike, it looks like Im most of the way through my tear down to start fixing and rebuilding but this is actually how I got the bike. So I get to start all over with whatever tank and seat I want without having to spend "extra" money because Im going to need them sooner or later lol. Im thinking about going Cafe style, but at the same time I want to give it the CR750 look... either way Ive got some time to decide which I will be doing.

First things Im looking for to start my rebuild are pretty simple and are going to be a requirment sooner than later.
New Gauges and exhaust. Since the gauges are shattered and the exhaust is non-existant this the easiest thing for me to see I will need lol.

my78k · « **Reply #1 on:** October 28, 2008, 09:30:00 AM »

I'd comment on here but I don't talk to the police!

Actually it looks like you have a fun little project there. Did you already remove the bars, fender etc or were they not there when you got it either?

Dennis

brady0706 · « **Reply #2 on:** October 28, 2008, 09:31:11 AM »

Make sure you take plenty of pictures for reference later on. Just my two cents. Gook luck!

kghost · « **Reply #3 on:** October 28, 2008, 09:34:57 AM »

No turning back now...

Good luck.

Findlater · « **Reply #4 on:** October 28, 2008, 09:37:07 AM »

Quote from: my78k on October 28, 2008, 09:30:00 AM

I'd comment on here but I don't talk to the police!

Actually it looks like you have a fun little project there. Did you already remove the bars, fender etc or were they not there when you got it either?

Dennis

Lol don't worry about the shirt its the only one I could find that I felt like getting dirty

Ive got the bars in a box and its hard to see in the photo because they aren't really in the right place but there is a set of clubman type bars on there now. As for the fender or anything else- what you see is what I got LOL.

moham · « **Reply #5 on:** October 28, 2008, 10:47:17 AM »

Don't know if you've gotten there yet, but the link below is a source to all the shop manuals, etc that will be indispensable to your project...

http://forums.sohc4.net/index.php?topic=17788.0

Good luck.

my78k · « **Reply #6 on:** October 28, 2008, 01:41:01 PM »

Hey I just noticed it shows you are in Ontario....where abouts? I live in Whitby about 30 mins east of Toronto

Dennis

Findlater · « **Reply #7 on:** October 29, 2008, 07:20:31 AM »

Im in London if there is anyone around with a little experiance who could help me out once in a while that would be awesome!

Thanks for the manual links aswell they will certainly by handy reference material.

my78k · « **Reply #8 on:** October 29, 2008, 10:31:53 AM »

It's a shame that I am so bad with names as I know there are a bunch of us up here and some much closer to you. I know we have guys in Kitchener, Hamilton, Dundas etc....I assume you can't be the only one in London. Lots of guys in the T.O. area though.

Dennis

Findlater · « **Reply #9 on:** November 01, 2008, 05:14:28 PM »

Hey my frame doesnt have a serial number but then engine has a serial of CB750E-2353(I or T)49 what year and model am I looking at here? I was told it was a 1970 this seems like 1974??

HavocTurbo · « **Reply #10 on:** November 01, 2008, 10:16:56 PM »

You don't have anything on the neck?

Findlater · « **Reply #11 on:** November 02, 2008, 08:36:39 AM »

nope

mystic_1 · « **Reply #12 on:** November 03, 2008, 04:50:50 AM »

The VIN should be stamped on the left side of the steering head. If the frame has been repainted it may have gotten covered up. I'd suggest stripping down that side of the neck to verify the VIN.

mystic_1

Findlater · « **Reply #13 on:** November 03, 2008, 07:11:11 AM »

yeah I might or might not sandblast the entire frame and repaint it. It doesn't look like anything has been deliberately filed off if you know what I mean. The frame is smooth and round with no flat spots. Also Im guessing the engine serial number doesnt help much in determining the actual year of the bike.

Working on the bike a little harder now and pictures to come. before I drained the oil to prep the engine removal I gave the kick starter a few pushes. Everything moved smoothly (except the big crack sound the kick starter gave me) and compression sounded good.

Pulled the carbs off and from the outside it doesnt look like they will need much cleaning but I definately need to rebuild them with new seals. Problem Im having now is whoever had the bike before me stripped almost EVERY screw on the engine so Im having a hard time getting them off. Even if the internals of the engine are in good condtion I really want to replace all these crappy screws.

PICTURES SOON!!!

my78k · « **Reply #14 on:** November 03, 2008, 07:42:31 AM »

Definitely get an impact driver if you don't already have one. It will make breaking those stripped screw drivers so much easier. I got mine for like 6 bucks at Princess Auto. Also, those carbs WILL need cleaning. They are famous for blocked slow jets. Do yourself a favour and when you have them off clean them very very well....especially the slow jets. It sucks putting them back on and then realizng you didn't get the cleaned the first time (or in my case the second time either!!)

Dennis

Findlater · « **Reply #15 on:** November 04, 2008, 06:54:53 PM »

REBUILD DAY 2:
Hey guys new photos as promised!
Carbs are now out!

The carbs don't look too bad on the outside we'll see what they look like inside later this week!

Clutch Cable disconnected!

Just had a quick look at the points? Im not sure if its what they are or what anything under this cover is but it looks to be in great shape!

Looks like its been dropped on its side once in the past or rested up against a wall!

Ready for the engine pull, just need to get the chain off and pull her out. Probably on thusday.

Anyways the engine seems to turn over great before I drained the oil so Im not sure if I'll take it apart and rebuild it other than just cleaning the carbs and rebuilding them. If nothing is wrong how much can I expect to spend in just pulling apart cleaning and putting back together? Maybe just replacing gaskets? My plan was to pull everything give it a look-over replace what I need to and have the frame re-painted before putting her back together. Also if someone could tell me if Im correct in assuming that those thingys were my points. Im really not too sure about motorcycle electrics.

my78k · « **Reply #16 on:** November 05, 2008, 05:23:13 AM »

Yep those are your points.

As for the carb rebuild? It is kinda difficult to say...I am sure someone can tell you the high side number but to be honest when I was working on my 78 that had been parked outside year round in our ever so forgiving climate (in other words beaten badly!!) I was able to reuse everything and didn't have a single leak or problem. The only issue I had was a damaged diapragm on the accelerator pump (which was only on the 77 and 78 models). So basically it was like 5 bucks for carb cleaner at Canadian Tire. It took alot of cleaning etc that probably could have been much easier with rebuild kits and new jets but I had more time than money...

Dennis

Findlater · « **Reply #17 on:** November 13, 2008, 06:37:46 PM »

So I finally found my VIN number under a little too much paint turns out my job here is a CB750 K4 and I plan on getting it sanblasted and repainted. The engine is out (pictures to follow when Im not so oily) and everything is coming off the frame nicely. The issue Im having is the screws on the engine are just stripping themselves when I try and take them off. Did anyone else have this issue or did they just really use metal this soft when making screws back then?

Any suggestions would be great!

mystic_1 · « **Reply #18 on:** November 13, 2008, 09:39:15 PM »

Quote from: Findlater on November 13, 2008, 06:37:46 PM

So I finally found my VIN number under a little too much paint turns out my job here is a CB750 K4 and I plan on getting it sanblasted and repainted. The engine is out (pictures to follow when Im not so oily) and everything is coming off the frame nicely. The issue Im having is the screws on the engine are just stripping themselves when I try and take them off. Did anyone else have this issue or did they just really use metal this soft when making screws back then?

Any suggestions would be great!

The stock case screws weren't metal at all, but are actually made of clay.

Really though, first make sure to use the largest phillips that will fit the slots. A #3 phillips fits pretty good. The stock screws are actually JIT (?) screws so unless you have access to tools from Japan you're stuck with phillips.

Second, an "impact driver" is the weapon of choice. Search that up.

Third, some screws can be gripped with visegrips, that'll get them out.

Drill out damaged screw heads to separate the heads from the screw, then once the cover is off the rest can be visegripped out.

Lastly, search these topics up, it's a common problem

http://forums.sohc4.net/index.php?action=search

cheers
mystic_1

BuffaloK3 · « **Reply #19 on:** November 14, 2008, 06:14:57 PM »

You have more pics of the bike in your avatar? Nice example. Shoot me a l ink or post them up.

Good project so far, will be starting mine this snow season!

mrbreeze · « **Reply #20 on:** November 14, 2008, 06:34:08 PM »

You can get allen head screw sets from members here......check the FAQ's.

Findlater · « **Reply #21 on:** November 29, 2008, 07:18:30 PM »

Just trying to finish my frame tear down and Im stuck on the front forks. How in the hell do I get them off? I've loosened the triple trees taken all bolts off I can see and Ive removed the wheel and front calipler. The forks are still on the bike cant get the triple tree off or the forks am I missing something? CB750 K4

problem solved... rubber mallet

Findlater · « **Reply #22 on:** December 02, 2008, 04:13:46 PM »

Got some new photos for you guys, the entire bike is apart now and the frame will be sent away for sandblasting and a new paintjob soon!

The wiring harness is pretty grimey!

The mess that is part of the wiring harness- to be honest I dont know what half the stuff is- other than my battery goes in this area lol.

The rest of the harness out of the bike!

All my crap sitting and waiting for its turn to be cleaned and rebuilt. The engine is coming up on that list!

Frame of my bike, Ive since gotten the entire front fork assembly off. If you look closely my upper triple tree is broken in 2 at the clamps. On both sides.... looks like I'll be needing one of those.

Instead of just cleaning it I decided to strip the paint off and start to polish the swing-arm. The black paint looked like garbage anyways.

Well Im off to take a shower I think the next photos coming out will either be of a newly painted frame or the start of my engine tear-down. Any advice so far always appreciated!

Thanks for the help so far everyone.

andy750 · « **Reply #23 on:** December 03, 2008, 05:23:59 AM »

Its hard to see in the photos but it looks like you have a head gasket leak -if thats the case I would spend the $$s to get that fixed (i.e. do it yourself - buy gasket etc) rather than spend money on painting the frame (which you could do yourself with some black rustoleum - looks just as good).

If you need a new harness (cant tell if its been hacked or not) then look at David Silver Spares website - they sell a K2 harness (and possibly a K1 - not sure there was a difference between the years - I did this and its so easy working with a new harness - remember its all colour matched i..e blue-blue, orange-orange...kind of hard to get it wrong ;-)).

Good job on the swingarm!

cheers
Andy

Soos · « **Reply #24 on:** December 03, 2008, 07:11:04 AM »

Is that a stock clutch cover?

l8r

Findlater · « **Reply #25 on:** December 21, 2008, 02:25:16 PM »

Time for an update with some new pictures!

Rocker Arms pulled and organized.

Valves look great! Little crud on the #3 but will easily scrape off.

Likewise on the pistons cylinders smooth and free moving

Cylinders in great condition

Everything looks good on this side

Sprocket is covered in old smelly crap- I'll be cleaning this soon

Clutch/Shifter looks good how do I tell if the gears are worn? gotta open the case still?

Engine as it stands today

Anyways so thats the engine currently. Im starting to wonder about cleaning what Ive pulled so far, painting the cooling fins like I want buying the new gaskets I'll need and put it back together. Everything internally is looking MUCH better than I had expected.

Thoughts from the group?

HavocTurbo · « **Reply #26 on:** December 21, 2008, 08:47:39 PM »

Mine looked about like that with 40k miles.

Only way to tell about the transmission is to split the cases and look.

Over all everything seems to be not half bad.

Industrial Cafe · « **Reply #27 on:** March 14, 2009, 05:59:41 PM »

Maybe I'm confused, you're polishing a steel swingarm?

dwmilton · « **Reply #28 on:** March 15, 2009, 04:04:57 PM »

Polish the pee outta it, and hit it with some clear hi-temp rustoleum...

Do they even MAKE clear hi-temp rustoleum?

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Author Topic: 1970 CB750 Rebuild (Actually a K4 based on the VIN) (Read 8062 times)

Findlater

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Findlater

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BuffaloK3

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dwmilton