CB750 monoshock frame mount

72texas350

72texas350

Been Around the Block
What is a good way to make a mount for the new monoshock on my SOHC CB750? I have already made the new pipes that will hold the mount. I just need to make, or buy, the clevis that goes down to the shock. How thick should the metal be on each side of the shock?
Would it be better to make my own mount, or is there someone who sells mounts that would be about the same price?

Here is a picture of the new part that I have already made and the bike so far.
 

Attachments

  • 10154055_10201416038077537_3694746824443426508_n.jpg
    10154055_10201416038077537_3694746824443426508_n.jpg
    89.4 KB · Views: 475
  • 604074_10201293884223767_1098565351_n.jpg
    604074_10201293884223767_1098565351_n.jpg
    87.5 KB · Views: 2,079
I just monoshocked my xs650... You'll need to double up that mount, and box it in preferably. Nothing worse than a 1000lb spring through the testicles at 100 MPH...

You'll benefit from moving the swingarm mount higher up. It will move the mount farther from the swingarm pivot, reducing the wheels leverage on the spring, and, if you like, it'll help you tuck the rear tire in farther.

What is the spring off of, and do you know the rate? A spring from a linkage bike will likely be too soft, you'll wanna look for one off of something like a 650 ninja that has a direct link between the swingarm and the frame.
 
mathil said:
I just monoshocked my xs650... You'll need to double up that mount, and box it in preferably. Nothing worse than a 1000lb spring through the testicles at 100 MPH...

You'll benefit from moving the swingarm mount higher up. It will move the mount farther from the swingarm pivot, reducing the wheels leverage on the spring, and, if you like, it'll help you tuck the rear tire in farther.

What is the spring off of, and do you know the rate? A spring from a linkage bike will likely be too soft, you'll wanna look for one off of something like a 650 ninja that has a direct link between the swingarm and the frame.
Click to expand...
I'm not sure I know what you mean when you say to box in the mount. And when you say double up, what direction are you talking about.
The spring is off of the same bike as the swing arm and wheel, a 1990 Honda NT650. The NT650 didn't use a linkage. It was mounted right from the swing arm to the frame.

I also have the mount as high as I can set it to still allow room for the rear wheel. I set the mount almost directly above the swing arm pivot point, as that is how it was mounted on the NT650.
 
I only see one tab on top that the spring mounts to, ideally it is tab - spring - tab. Also known as "double shear". A joining piece between the two tabs is a good idea to be extra sure the tabs don't bend to the side under extreme force.

I looked up some pictures of the honda, must be a really stiff spring, the wheel has a ton of leverage on it. If you keep the mounts in the same area and the bikes are around the same weight, and the spring is at the same angle it should work out close.

Looks cool! Single sided swingarms are neat.
 
mathil said:
I only see one tab on top that the spring mounts to, ideally it is tab - spring - tab. Also known as "double shear". A joining piece between the two tabs is a good idea to be extra sure the tabs don't bend to the side under extreme force.

I looked up some pictures of the honda, must be a really stiff spring, the wheel has a ton of leverage on it. If you keep the mounts in the same area and the bikes are around the same weight, and the spring is at the same angle it should work out close.

Looks cool! Single sided swingarms are neat.
Click to expand...

Oh I see what you're saying. I have tabs on both sides of the spring. That picture was taken while I was still trying to measure everything out before adding the second tab. I was planning to add a joint between the tabs, but haven't done it yet. I will add it when I can throw the frame on my bench after I take it all apart again.
 
I am always impressed with the ingenuity of the conversion, but (always a but), the longer wheelbase slows handling, and I can't figure out the real performance improvement of one shock over dual shocks.

So I can conclude the mono-shock, SSS is essentially for looks, even if handling is less crisp?

The unsprung weight isn't improved either. My understanding is SSS's are good for rapid tire changes (great for racing) at the compromise or increased weight.

So heavier bike = slower bike.

Slower, less handling, unique look....Is that the story?

Not ragging on the work....the work is impressive, and it will look unique. As a show piece of craftsmanship, it is very good. So I assume that is the goal? Rather than performance?
 
Midlife, he did switch to a lighter swinger that is single sided and has to take a mono shock, the longer wheelbase is too bad, but that hawk swinger is going to be way stiffer and should be lighter then the oe steel.
 
mydlyfkryzis said:
I am always impressed with the ingenuity of the conversion, but (always a but), the longer wheelbase slows handling, and I can't figure out the real performance improvement of one shock over dual shocks.

So I can conclude the mono-shock, SSS is essentially for looks, even if handling is less crisp?

The unsprung weight isn't improved either. My understanding is SSS's are good for rapid tire changes (great for racing) at the compromise or increased weight.

So heavier bike = slower bike.

Slower, less handling, unique look....Is that the story?

Not ragging on the work....the work is impressive, and it will look unique. As a show piece of craftsmanship, it is very good. So I assume that is the goal? Rather than performance?
Click to expand...

I know the longer wheel base isn't ideal, but like you said it's more about the looks. I'm not really making the bike to be raced. This project is more about trying pretty much anything that pops into my head and making it look nice in the mean time. The Hawk rear end is lighter than the CB750's mostly because of the wheel, I think. I don't know the exact weight difference, but holding the stock rear wheel in one hand and the Hawk's in the other there is quite a noticeable difference.
 
Is it lighter? He added a lot of steel, and the amount of aluminum is quite a bit. SSS have to be rigid, to handle torsional loads, so require a large cross section.

In addition, the frame should be strengthened at the SSS mount. the frame is not designed for the type of torsional loads at the pivot. Those were reduced because of the dual shocks.

I am not knocking it, and if looks are the goal, it is an interesting look and will get attention.
 
measured axle to axle?
1969-honda-cb750_600x0w.jpg

it looks way way longer than this (stock 57")

just coming from personal experience, the cb750 is VERY easy to turn into a tank. it starts off as a very stable bike and adding wheelbase or decreasing offset or switching to wider wheels only compounds that. I've found on my own 750 with stock wheelbase and stock trail but using a zzr1200 front end and rear wheel, it's actually slow to turn in and lacks the original maneuverability of the stock version, this is something I need to fix now, so before you get too far into the build, you might want to consider options to either decrease stock trail moderately or decrease wheelbase
 
You must log in or register to reply here.

DTT Light or Dark

  • DTT Light
    • www.jadusmotorcycleparts.com
    www.lostapostle.ca/
    www.sparckmoto.com

    Spread the Love

    Back
    Top Bottom