74 CB750 USD and Mono build

[chowpay]

With the suggestion of a edneeves decided to post my 750 build progress.

I see a lot of great builds on this site so hopefully this one wont bore you guys too much.

I bough this 74 last year with the idea that I could use it to putt around town. But its kind of a pig and I didnt like how it handled so one thing led to another and I pulled it all apart:

I bought the benji set a a while ago, kinda regret it now because my taste have changed but you use what you have

I didnt like how long it is so I decided to shorten it... wont be the most comfortable thing but I'm small and I like the look better. I ended up taking off 4 inches off the end too.

I'll weld up the hoop later

The swing arm seemed so short on the 74 , for the mono shock setup I wanted to do, I decided to swap in a later model .. i think its a 79
Swap was pretty easy I just had to mill the long end to fit the frame and lathe off the inner race:

On to the mono shock!

I noticed not many people post up how to make the top link ... its kinda important. After checking out a few bikes I went with this. Its DOM milled with a 3deg angle to fit into the CB750 frame

I'm using a donor shock from a 96 CBR1000. Which I know has a linkage. Now I can't replicate the linkage with the stock swing arm but talking with one of the RnD guys at honda he suggested as long as I keep the correct ratio it should work fine. To get this ratio down I made a mock strut:

Match the eye-to-eye

Match the travel length

Add a couple of 10mm lines and tada we have mock strut

Figure this will take the guess work from when I get to welding the upper swing arm support

Now I can't get the right height without the right forks.
here's the doner 2005 GSXR fork.

Got to use my new 20 ton .. that was fun. the "pop" when the stem finally pops out will scare your balls (scared mine)

*Be sure to support the closest point of where you're actually pressing it out. I got lucky, probably because I was going so slow, that nothing got distorted (bent or cracked). if you're gonna do this support the triple.*

The stem is half an inch too short so I made this plug this I made a plug out of 6061 alloy :

V-grooved both the plug and the stem pieces, tig'd it up filling the V and rough lathed off the excess

This was all kosher according to an engineer i've been bouncing Ideas off of.

But one thing I didn't consider.. What is the alloy type of the stock steering stem? does anyone know?

Still lots of work to do!

 

[neevo]

There you go! Looks like you've got some ideas and the thought process is fascinating. Keen to see more updates.

 

[chowpay]

Thanks!

Thinking of moving the electrics into the frame now that I found a super small battery I can use. With that, this leaves my rear seat open. Anything thoughts? I was thinking about making a hidden oil tank to go under the seat

 

[ILoveThumpers]

Got use my new 20 ton .. that was fun. the "pop" when the stem finally pops out will scare your balls (scared mine)

The stem "popped" because you were deforming the tree by supporting it that way. It should press out smoothly, but you have to support the tree around the stem, not just on the sides. I'm surprised you didn't crack it.

Double-check when you put it back together that it didn't warp. If your forks don't go back in smoothly, it's likely the top and bottom are no longer aligned properly.

What battery did you choose? I just found the anti-gravity battery company offerings; way cool stuff!

-Deek

 

[chowpay]

Yoyo,

As for the pop I don't know if its deformity.. Good news is they came back together pretty well with no binding or anything. Maybe I lucked out good to know though thanks!

We looked at the lower and didn't find any stress marks. We're guessing the pop was due to the corrosion, found a lot of alumium oxide (white stuff) around the hole.

Here's the battery:

https://www.pegasusautoracing.com/bigpicture.asp?RecID=9401

They have a bunch of models

 

[ILoveThumpers]

Good news! A tip for the future; I keep several short lengths of different diameter black iron pipe around the press just for these occasions. It's always best to support the piece as close to the point of force as possible. Corrosion does cause parts to freeze so I'm sure at least some of that sudden release was due to that!

Pegasus has some nice products... I forgot about them, actually. Thanks for reminding me they are out there!

-Deek

 

[chowpay]

Looking for one powerful enough to run the starter too. Relocating the battery under the tank, one option someone proposed to me is that I can use a CRF150 battery w/good cables and a short distance to the starter I should get enough to turn over the motor.

 

[chowpay]

Though backwards and flipfloped they mounted on with the new bearings with ease. (they are backwards because they got in the way when I had it set on the floor):

 

[GB400 fan]

watching!

 

[chowpay]

Finished the oil tank

 

[zshulk56]

That oil tank really does it for me. No homo...... but seriously I am jealous of your fab skills. Keep it up excited to see how this turns out. You planning on any engine mods and for the monoshock are you just using the original swingarm and wheel or using a modern swingarm to match your front end?

 

[vbtravisd]

Yeah man... that oil tank is killer! I will be watching this one close... I want to go monoshock on mine, but I am using a GSXR swingarm... or at least thinking about it.

 

[chowpay]

Thanks guys,

@zhulk Not sure about the motor yet. But since its out of the bike it is tempting to just drop in an 800kit but we'll see. I would like to do the 2carb setup instead of the 4. I think thats a lot cleaner.


As for the swing arm, it seemed so short on the 74 so I decided to swap in a later model .. i think its a 79
Swap was pretty easy I just had to mill the long end to fit the frame and lathe off the inner race:

I have since replaced the inner plastic race with machined copper ones. I plan to put a mount on the swing arm with a U brace for the shock once I work out the ratio. The ratio is important because the shock is off of a 96 CBR, which uses a linkage. So I have to find the ratio that accurately emulates the linkage.

I was going to use a modern swingarm in the rear but They're all too "thick" looking. Which isn't necessary unless you're using aluminum. The steel (to me) gives it a more classic look. This is a restomod.

 

[Finnigan]

I'll be watching, great work!

What kind of welder do you have?

 

[zshulk56]

If you got the time and $$ I would say go for it your gonna have a sweet looking bike might as well make it faster while you're at it. The two carb set up does look pretty slick. I like the idea of the keeping the "original" swingarm and the restomod got to keep it classy.

 

[chowpay]

I'll be watching, great work!

What kind of welder do you have?

Htp 221 inver tig. It's awesome.

If you got the time and $$ I would say go for it your gonna have a sweet looking bike might as well make it faster while you're at it. The two carb set up does look pretty slick. I like the idea of the keeping the "original" swingarm and the restomod got to keep it classy.

Hmmm maybe when I get to that point I'll find a good deal somewhere

 

[50gary]

When I saw the way you pressed the stem I was worried about bending or even cracking the lower Triple clamp. I've pressed out many of these, the last one being a 2007 GSXR 750/600 and I recommend what "ILove Thumpers"said. Support the underside of the T-clamp with heavy walled tubing as close to the diameter as you can. I would check your T-clamp for straightness before installation. Not trying to beat you up here just a suggestion.
Cheers, 50gary

 

[chowpay]

When I saw the way you pressed the stem I was worried about bending or even cracking the lower Triple clamp. I've pressed out many of these, the last one being a 2007 GSXR 750/600 and I recommend what "Suzuki"said. Support the underside of the T-clamp with heavy walled tubing as close to the diameter as you can. I would check your T-clamp for straightness before installation. Not trying to beat you up here just a suggestion.
Cheers, 50gary

You're correct. I ended up getting a piece of black piping for the 2nd pair I pressed out. Luckily nothing went out of plum when I re-assembled the front end. I think its due to the fact I pressed it out really slowly.

I actually picked up another triple lower just incase since I found it super cheap on flebay but found that my original was not distorted and bolted up without binding.

 

[50gary]

Cool, glad everything worked out, BTW I'll also add my kudos to your oil tank, super job. I have a Miller Syncrowave 250 TIG water cooled. I like the idea of the newer inverter jigs.
Cheers, 50gary

 

[chowpay]

Cool, glad everything worked out, BTW I'll also add my kudos to your oil tank, super job. I have a Miller Syncrowave 250 TIG water cooled. I like the idea of the newer inverter jigs.
Cheers, 50gary

Thanks, the syncrowave is the workhorse of transformer tigs. I was very very close to going that route before I started to research inverter tigs.
Its crazy at 220 Amps it doesn't even kill by 40amp switch