Topic: Ugly CB750K4 Rat Resto

[Stev-o]

My wife and I had our first baby yesterday. A girl!

Congrats!   

Coincidently, my nephew [and wife] in Florida had their first baby yesterday too, a boy named Ziggy!!

BTW - the head cover is on the way to you.

[SOHC4 Cafe Racer Fan]

Congratulations!  I hope she grows up to ride it!

[Jake88]

Thanks, guys!  First one, so pretty excited.

BTW - the head cover is on the way to you.

Big thanks to Stev-o for helping me out with a valve cover!  It arrived today.  Thanks for throwing in the sweet shirt! Set it in place without a gasket same as the other And problem solved!  Someone definitely took a lot of material off of the original.  I may have been able to make do with the old one, but this replacement makes me feel a lot better.   

Also, got those fork seals out by warming up the top part of the fork lower and pried applying steady pressure with a screwdriver. 

[Jake88]

Managed to sneak out to the garage for a few minutes And have a little update.  I've been thinking about the swing arm a bit lately. After I got the bike stripped down a while back, I was testing the swing arm for any play. It had some side to side wiggle. I put a grease gun on it and with a little effort got it to take some. After that, things tightened up and there was no play.  Definitely some wear has taken place.

So I went out and removed the swing arm. The bolt and the collar came out pretty easily. Bolt is in great shape, zerks at both ends. Coller has some visible wear and pitting.  Other parts I came up with include two metal caps, in which sit a plastic ring. Between this ring and the bushing there was a felt washer on one side. The other one must have bit the dust at some point. 

With my digital calipers, I measured best I could. Starting with the bushings which I measured on both horizontal and vertical plane. 
Right horizontal - 21.53mm
Right vertical - 21.53 mm
Left horizontal dash 21.55 mm
Left vertical dash 21.48 mm

And the collar. I measured both ends and tried to find the largest and smallest readings.
Large - 21.35 mm
Small-21.32 mm

Large - 21.36 mm
Small - 21.33 mm

It sounds like the collar OD should be 21.392 mm and the bushing ID should be 21.422 mm according to my readings on another thread.

I've included some pictures of the collar ends. One shot of the best looking view, and one shot of the worst looking view on each end. 

I guess I could buy some brass bushings and clean up my collar And keep it full of grease. That would close the tolerance some but would by no means be perfect. 
Or try to find a new collar. My initial search leads me to believe that that could be tricky. The used ones I saw on eBay looked about like mine or worse. 

Just throwing this out there, I'm trying to keep from spending gobs of money on this bike and it's mostly going to be for evening joy rides and shorter excursions.  I do, however realize that this is a fairly important component.

Anyone have any thoughts or recommendations?

[Jake88]

Pics

[Jake88]

Other end

[Kelly E]

I bought a swingarm needle bearing conversion kit for my 74'  CB550 K0 and it solved all of those problems. It was about $110 and now it's really smooth action and no play at all.
I think there was 750 kits as well.

[seanbarney41]

Kelly, how many miles you got on that needle bearing swingarm so far?

[Kelly E]

Not that many yet, too many bikes, so little time.

[seanbarney41]

I have a set of those I was gonna use, but got scared they would not be durable.  Sourced bronze and nos collar instead.

[Kelly E]

I have a set of those I was gonna use, but got scared they would not be durable.  Sourced bronze and nos collar instead.

Why wouldn't it be durable? We have several bikes with needle bearing swingarms stock. The 82' CB900 F, the 84' Interceptor 1000, the 84' Sabre 700 and the 80' Suzuki GS1100 E.

[MauiK3]

I'd say new bushings and collar, looks pretty worn

[desertrefugee]

Brass bushes that went into my '79 cbx made a noticeable improvement over the plastic ones that Honda installed.  For the life of me, I cannot fathom why they chose plastic in that application.  I don't recall if the 750 came from the factory in plastic. Did they?

[BenelliSEI]

Knock the high spots off, so they don’t rip onto the new bushings. Put ittogether and grab the end of the swing arm. If it’s reasonably tight, with NO side to side play, save your money for another part.

[Jake88]

Knock the high spots off, so they don’t rip onto the new bushings. Put ittogether and grab the end of the swing arm. If it’s reasonably tight, with NO side to side play, save your money for another part

I think I will go ahead and buy the bronze bushings, bolt it up and see what I’m working with. Then I can always try to source a new collar if I don’t like what I find. I am interested in that needle bearing setup, too.

I did a little assessment of my fork situation last night.  Again, I’ve got the 74 lowers and innards with longer than stock tubes and also have a pair of K8 lowers and tubes.  Here’s how some of the parts compare between years

K4 Spring- 18-11/16”

K8 spring- 19-5/8”

K4 damper pipe- 9-1/16”

K8 damper pipe- 8-9/16”

The oil locks are different design but I think either could work in the K4 lowers as the bottom of the inside is just flat. On the 78 lowers, there is a recess on the bottom that the oil lock sits down in.

So I think I’ll use K8 tubes, K4 lowers, K8 springs, K8 damper pipe and K4 oil lock. With that combo, the tops of the spring come about flush with the top opening of the tube.   Throw in a new seal and the circlip and I should be good to go.  Let me know if there is anything wrong with this combo of parts

[BenelliSEI]

There’s nothing wrong if it all stacks in nicely and works! Good luck and post your results.

[Jake88]

Hello. I wanted to give a quick update and let people know that this project is not died.  We had a kid and March And it turns out little babies require a lot of attention! I also had the opportunity to buy a three-wheeler that I've been wanting for a while and used what little free time I had to do a quick and light restoration on that so I could use it for yard work.

As for the CB750, I have slowly been cleaning and painting bits and pieces. I painted the frame a week ago and more or less got the motor button back up with the valve cover inside covers back in place.  I did not take the frame down to metal, instead just sanded the existing paint, hit it with a very light coat of primer And then some semi-gloss rustoleum.  I think my next move will be getting the motor back into the frame, probably using the "lay on it's side" method.  Hopefully I can accomplish this without dinging up the paint too bad.  I ground off the lip on the lower right side engine mount that should give me a bit more clearance. Tapered bearings are all ready to go in and forks are assembled and ready as well. 

I'm excited to get it back on its wheels and will be putting a set of super bike bars on it as well. I won't be rewiring anything if I can help it, but do want to clean up the wiring harness before reinstalling that.

I will try to keep this up today as I plug away.

[BenelliSEI]

Jake..... really like the trike! A neighbour has one that looks like it’s been left outside for +30 years, but every time he uses it, runs like a top! It has an enclosed chain case and a few years  ago it was making such a clatter I forced him to let me change the chain and sprockets (I don’t think they’d ever seen the light of day). Great machines, so long as you don’t turn in too suddenly......

[Jake88]

Jake..... really like the trike! A neighbour has one that looks like it’s been left outside for +30 years, but every time he uses it, runs like a top! It has an enclosed chain case and a few years  ago it was making such a clatter I forced him to let me change the chain and sprockets (I don’t think they’d ever seen the light of day). Great machines, so long as you don’t turn in too suddenly......

Thanks! It's a good time. This model is shaft driven, so no chain to worry about!  It seems like the majority of three wheelers out there have undergone years of abuse. But like you said, they take it well!

I made a little progress on the 750 today.   I had a few hours to mess around in the garage so decided to get the motor back in the frame. I was expecting it to be a bit of a PITA, but the frame slipped over the motor lickety split. I took the oil pan off to give me a little more clearance.  I popped a few engine mount bolts in and left it on its side. I need to reinstall the oil pump, gasket and oil pan before tipping her upright.   

Any recommendations to make my life easier while installing the front fork, swingarm and wheels? I feel like I'll need to set the whole frame and motor up on something to give it some height off the floor.

Thanks,

[Kelly E]

Put the centerstand back on so you'll only have to block up the front and get a buddy. You'll have it upright and ready to build in a few minutes. We hobble the centerstand to the frame with a strap so it can't fold back up.

[Jake88]

Put the centerstand back on so you'll only have to block up the front and get a buddy. You'll have it upright and ready to build in a few minutes. We hobble the centerstand to the frame with a strap so it can't fold back up.

Excellent idea! Thanks.

[Gurp]

Man, I understand the limited time you speak of. Lol
The good thing is the older they get the more time you get.
My 4 and 5 year old have been "helping me" in the shop for over a year now as long as I don't use power tools.

Really nice ATC you got there. Seems like you got it all going in the right direction buddy!

[Jake88]

Thanks, Gurp!

I think I ran into a snag and am looking for some advice.

The other day I installed the swing arm into the frame. I had replaced the old bushings with new brass ones. I polished up the collar and it fit into the bushings before they were installed. After the bushings were in the swing arm, the collar fit rather tight. I'm thinking maybe the bushings aren't precisely aligned or something. But what I'm more worried about is the following...

In my mind, the collar has to be proud of the outside of either bushing just a bit because it should be getting pinched between the frame (I've got the metal caps installed in the equation) when the swing arm bolt is installed and tightened. The collar stays stationary and the bushings rotate around it. Is this correct??  My swingarm collar did not appear to protrude at all outside the plane of the bushings. When I installed the bolt and tighten things up, the swing arm was very hard to move leading me to believe that The outside face of the bushings is what is contacting the inside of the metal caps and getting pinched. I can move it but it's pretty darn tight.

Can someone please shed some light on my situation?

Thanks!

[seanbarney41]

yup, your understanding is spot on, and probably your diagnosis of why it is tight.  I believe others have had to face down their bronze bushings slightly as well.

[Jake88]

yup, your understanding is spot on, and probably your diagnosis of why it is tight.  I believe others have had to face down their bronze bushings slightly as well.

.

Any recommendations on the best way to do that? The bushings are not coming back out of the swing arm. I've got a good mill file, I could carefully remove material trying to keep it as flat as possible but won't be perfect. I've got an angle Grindr and belt sander also but that sounds like asking for trouble.