Author Topic: My First CB 750 and rebuild (Read 4381 times)

royinla1 · « **on:** April 30, 2016, 02:46:44 PM »

I bought this 1978 CB 750K last July and it has sat in my shed since. Here's my introduction on the forum:
http://forums.sohc4.net/index.php/topic,149766.msg1732732.html#msg1732732

So, here we are almost a year later (and 3 kitchen projects, 1 bathroom project, two lawn projects, and one very wet winter later) and I've finally gotten started on my bike. During this winter I have read over some of the rebuild threads and the projects threads. I bought "the book" and this spring started cleaning up the bike and parts. So now I'm finally ready to get started with the building process. I just received my gasket set and have pulled the piston to clean them up. I'm going to try to upload some photos here soon.

One thing I have found interesting is that to me after seeing photos and write ups of other bikes (like Mouse) and what Mark recorded in his book, mine doesn't look as bad as I'd thought.

so maybe after some more "knowledgeable eyes" view my photos I'll have a better idea where to move on to. I'll get those pictures up here soon and look forward to the replies.

bender01 · « **Reply #1 on:** April 30, 2016, 04:54:03 PM »

Cool! Ive just started to put an engine back together! I have revived a few but my current project came i plastic tubs!

royinla1 · « **Reply #2 on:** April 30, 2016, 06:42:20 PM »

It's been a while since I posted my introduction, so I don't remember how to post pictures on here. This is a trial to see if I remember.

OK, I figured out I needed to reduce the photographs' sizes, but how do I post the pics in the message so I can write about each one, like I see others do in their threads?

Lets see if this works. OK, I don't know if this is right, but above is engine from the right, rear.

mystic_1 · « **Reply #3 on:** April 30, 2016, 07:26:17 PM »

In order to post the pictures in-line with text, you'll need to post them on photobucket or flickr or wherever and then use the IMG and /IMG tags to insert the images into your text.

For example:

Code: [Select]

[img]https://farm2.staticflickr.com/1612/25728016921_62bb4d0c6a_b.jpg[/img]
Becomes:

mystic_1

royinla1 · « **Reply #4 on:** April 30, 2016, 07:50:35 PM »

Thanks! It's getting late and I'm tired, so tomorrow I'll create an account on one of these.

royinla1 · « **Reply #5 on:** May 01, 2016, 07:45:34 AM »

Created a flickr account, so let's try out this image posting.

Here is another view of the engine casing.

Looking into crankcase for pistons 1 and 2.

royinla1 · « **Reply #6 on:** May 01, 2016, 07:56:22 AM »

Yes! got it working. Thanks, Mystic_1.

So here are some more pictures and my noobie comments.

Well, this looks to be in good shape.

Cleaned these up a bit, then oiled them.

Looking into the gas tank. And here is a close-up. Yes, that's rust inside. Any thoughts?

I'll try to load some more photos later today. Any comments, suggestions are welcome.

I will say this, I'm not looking to return this bike to showroom finish. I want it to run and get me from point A-B. I'm kind of like a couple other members on here who rebuilt their bikes and didn't really mind the "used" look. The two BMW airheads I owned were like that - but they ran like clocks and never left me stranded anywhere. I'm looking to use this for a commuter to work when the weather is right (about 13 miles one way) and for fun on the weekends, maybe short trips an hour away.

mystic_1 · « **Reply #7 on:** May 01, 2016, 08:11:06 AM »

BTW, now that you've got that working, you no longer need to resize your photos before posting. If you post very large images, the board automatically reduces their size for display but allows you to click for a bigger image.

You can see this behavior in the image i posted above.

mystic_1

royinla1 · « **Reply #8 on:** May 01, 2016, 08:11:49 AM »

A view of the pistons.

Pistons 3 and 4.

Inside of piston 3.

The rings look to be in good shape. I haven't gotten to check them in the block yet, but using Mark's method, I hope to do that over the next couple of days.

The top of piston 1. It's the only one that looks like this. According to Mark's book (if I'm reading right) there was water in there at some time, causing the pitting.

Ok, give me your thoughts, opinions, ideas. I'm ready to start putting the heads back on with the gaskets I received. Then I can turn the engine as required and change out the other gaskets and check the inside of each section. Thanks for any input you have to give me.

royinla1 · « **Reply #9 on:** May 01, 2016, 03:33:55 PM »

Sorry for the double posting, but I am still getting used to using this forum.

This afternoon I spent time cleaning under the rings and checking the ring gaps in the bores. If I did it right they all seemed to be in range. I also honed the bores - thanks to AutoZone tool loans. I cleaned out the oil holes on the piston and started planning my next step. I opened my gasket set and began planning to put the pistons back on. I read through Mark's sections on that and got my ring compressors ready (3 inch hose clamps) and 1/2 inch blocks prepared. Now mingling to re-read the reassembly section of the book and make my notes. My biggest fear is I will forget to put in an o-ring or something.

May not get to work on her until next weekend, but I will keep posting as work is done. I'm not a real good mechanic but I do enjoy working on old bikes!

royinla1 · « **Reply #10 on:** May 07, 2016, 08:35:41 AM »

I was able to take some time today and get a little work accomplished on the engine.

I put the base gasket on and then took it off and turned it over, as it seemed to be rubbing on the tension chain.
I added the o-rings to the two center studs after this photo.

I sorted the gasket set I'd received, but now I have some questions. Looking at this photo, I'm not sure what the two gaskets are in this photo on top left? (nothing was labeled in the set when it arrived, just all packaged together).

According to the parts listing I have from the downloaded manuals, I should have two "knock pin 12x15" on the two outer edge, front studs. Part number 11 in drawing.

Is one of the gaskets above those knock pins? Or are those the metal flanges that are sticking out of the bottom of the cylinder base? Man, it would have been great if this engine had not been disassembled when I bought it. That's why I'm having so much trouble identifying pieces and parts. So I could really use some help on this.
Thanks in advance for any assistance or guidance.

royinla1 · « **Reply #11 on:** May 07, 2016, 02:33:58 PM »

After reading through two more threads I just found out the green gaskets are for the valves. But I'm still not sure about the black ones and if two of them go on the studs, against the case under the cylinder head?

royinla1 · « **Reply #12 on:** May 10, 2016, 06:39:29 PM »

I finally had the time last night to read through a few other threads on here, something I'm not getting much time to do lately. But when I did, I found out what these are:

Yes, those are the knock pins! Now I'm ready to start putting on the cylinder head. I'll have to re-read that section of the book again. Maybe this weekend I can get it done.

I also received my two JIS screwdrivers from Japan this week and this evening took a few minutes to try out the largest one on trying to remove some screws from the clutch cover. YES! It worked like a charm. It's one of the impact screwdrivers made by Vessel. Of course, I sprayed these with a super strength rust removal I picked up in AutoZone about a week ago. That might have helped too. I'll be spraying the other screws the next couple of days and then try to loosen them this weekend.

I'm feeling better about all this now that I'm getting some work done and picking up the right tools. School will be over soon and I can have more time to read through postings and threads. More to come on my rebuild of ...? (haven't named my bike yet like others have on the forum, but I'm thinking on it)

royinla1 · « **Reply #13 on:** June 02, 2016, 02:57:07 PM »

School is out and I'm finally getting back into rebuilding my bike.
Today, I was trying to put the cylinder over the pistons. I'd come up with the "great" idea of trying to wrap a piece of cut/folded aluminum can instead of using Mark's idea of hose clamps. So, I cut out and bent strips of an aluminum soda can and then put cable ties around those. I had brushed oil on the cylinder edges and the rings prior to this and had the gasket rubber banded to the cylinder (as I'd seen in other project reports).

But, this did not work as I'd hoped. The aluminum was too thin (even folded over) to keep from getting caught in between the piston and the cylinder. So then it occurred to me to use a couple of very large cable ties that were wide enough to cover both rings on the cylinders.

Sorry I forgot to take pictures of this set-up, but it worked!

Now I'm ready to start putting in the o-rings and getting ready for the next step. I've been reading more of the project builds and trying to determine exactly were the rings and knock pins go. Thanks to SKTP and brandEn for their projects and write-ups.

bender01 · « **Reply #14 on:** June 02, 2016, 05:29:44 PM »

Knock pins! Im missing one so far.

koendd · « **Reply #15 on:** June 02, 2016, 10:36:12 PM »

you should have cleaned the head first...
Is can see residu of an old head gasket... New one won't sit flush now.
Why didn't you repaint the engine while you were there?

good luck with the project though!

rickmoore24 · « **Reply #16 on:** June 02, 2016, 11:22:13 PM »

Hi, Nice work so far! Did you replace the rings on the pistons with new ones? I didn't see how many miles were on the engine but I'd probably do a hone and re-ring since she's all apart now and the pistons are in spec. Just my 2 cents, if you did I must have missed it reading through the thread. Cheers!

Rick.

royinla1 · « **Reply #17 on:** June 27, 2016, 03:55:22 PM »

Quote from: koendd on June 02, 2016, 10:36:12 PM

you should have cleaned the head first...
Is can see residu of an old head gasket... New one won't sit flush now.
Why didn't you repaint the engine while you were there?

I did clean off more of the old gasket with what I could get at my local Autozone. (Small town in south LA and on a budget. After finding and watching Hackaweek's videos (Thank you!!!!!!) I did the best I could and forged on. You're surely right - I'll probably be pulling this thing apart and redoing it.
No painting for now. My objective is to put it back together and see if she even runs, since it came to me in parts already dismantled.

royinla1 · « **Reply #18 on:** June 27, 2016, 03:59:54 PM »

Quote from: rickmoore24 on June 02, 2016, 11:22:13 PM

Hi, Nice work so far! Did you replace the rings on the pistons with new ones? I didn't see how many miles were on the engine but I'd probably do a hone and re-ring since she's all apart now and the pistons are in spec. Just my 2 cents, if you did I must have missed it reading through the thread. Cheers! Rick.

Another good point. After reading "The Book" and going by the measurements Mark mentions, they all seemed to be in range. So I pushed on to get the engine back together and see if it runs. But I may be breaking it back down later and redoing it all. Fingers crossed.

bender01 · « **Reply #19 on:** July 05, 2016, 08:52:26 PM »

This piston rings have been worrying me.I still havent gotten it to the shop to axe it out to 836/65mm. But would lightly seated zip ties on the rings work? Surely they are thinner than hose clamps. But once the juggs are coming down is there that much room to use hose clamps? Probably since its posted many times. Also my new pistons are scalloped on top? For the valves! They go to the exhaust side?

Davez134 · « **Reply #20 on:** July 06, 2016, 12:39:54 AM »

Quote from: bender01 on July 05, 2016, 08:52:26 PM

This piston rings have been worrying me.I still havent gotten it to the shop to axe it out to 836/65mm. But would lightly seated zip ties on the rings work? Surely they are thinner than hose clamps. But once the juggs are coming down is there that much room to use hose clamps? Probably since its posted many times. Also my new pistons are scalloped on top? For the valves! They go to the exhaust side?

Make sure the bottoms of the cylinders have a taper and just compress the rings manually with your fingers, letting the weight of the jugs fall over each ring one at a time. I've tried clamps, ties etc... This way works just fine and easier than you may think.

blackbike · « **Reply #21 on:** July 06, 2016, 01:36:39 AM »

To get rid of the rust in your tank: put a handfull of ball bearings in your tank and spend an hour rotating it in all directions. Take out the balls and rinse with petrol...repeat if necesarry.....

Verstuurd vanaf mijn GT-I9195 met Tapatalk

SOHC4 Cafe Racer Fan · « **Reply #22 on:** July 06, 2016, 07:05:34 AM »

Quote from: blackbike on July 06, 2016, 01:36:39 AM

To get rid of the rust in your tank: put a handfull of ball bearings in your tank and spend an hour rotating it in all directions. Take out the balls and rinse with petrol...repeat if necesarry.....

Verstuurd vanaf mijn GT-I9195 met Tapatalk

You will need more than dry ball bearings to eliminate the rust. Many have used solutions such as vinegar or The Works (toilet cleaner). Another solution is to simply take the tank to a radiator shop and have them clean the inside of the tank (costs about $20).

royinla1 · « **Reply #23 on:** July 20, 2016, 05:20:49 PM »

Summer has passed by way too fast. Now here I am almost a moth later and just getting back to this forum. With my wife's surgery and then her hurting her knee, it's been a busy month. So, here is where I'm at:
1. I am ready to put the cylinder head cover on, but am waiting to get some replacement screws as two of them were bent slightly.
2. I ordered seals for the clutch cover and kick starter shaft to finish putting that back together.
3. Carburetors! With the heat here being so bad and my big metal shed being like an oven, I pulled my carburetors (which were assembled on the rack) inside and slowly I've taken them apart, cleaned them in Simple Green and gas and carburetor cleaner. I ordered kits to rebuild these as well and am now waiting on them to come in. So, I've watched Hackaweek's carburetor videos, but his were not the '78 model. So I have found only one other video on taking these apart and going over each piece.

Is there a thread or any videos someone knows of that could guide me in building these back? Yes, I took lots of photos as I did my disassembly work, but having visuals always helps.

Here are some pics:

These are of course prior to my disassembly of them and before they were cleaned. I'll have to take some pics of the parts now.
Sorry I've been off this so long, but life has seen my busy elsewhere.
Thanks for any assistance or guidance on the carburetors.

royinla1 · « **Reply #24 on:** July 20, 2016, 05:53:52 PM »

More pics of the carbs as I disassembled and before I cleaned them:

royinla1 · « **Reply #25 on:** July 29, 2016, 01:01:00 PM »

Help! I am putting my 78 carbs back together and even though I took good photos of the parts as I worked on removing them, The carb choke lever arm that connects the 2nd and 3rd carbs was bent up and not rotating together when I disassembled it. Can anyone provide me a photo of your choke lever assembled - maybe two or three photos in different positions? I've been going through the carb section and projects but haven't found any good pics yet.
Thanks.

Ericcb750 · « **Reply #26 on:** July 29, 2016, 01:48:01 PM »

Hey Buddy, send me your e-mail or cell and I'll send you some photos. I've re-built those darn carbs many times and provided another member the same exact photos.... That choke linkage can be a REAL PAIN. the key ist that dinky little spring that bends if the wind blows too hard.... Let me know buddy. I have a 78K also and if you need any help... just ask

You're in the right place. There's also a member, flybox and harisuluv (re-builds these professionally) and they are a huge wealth of knowledge on getting these PD's nice and clean.

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Author Topic: My First CB 750 and rebuild (Read 4381 times)