Topic: CB550 Frame bracing help needed!

[FunJimmy]

This little CB550F just rocks in the canyons since upgrading the suspension and brakes.  My new concern is that the additional cornering and braking forces are being transferred to the frame and since I’ll be pulling it apart for powder coating this winter, I thought it would be a good time to brace or gusset the frame. I can’t seem to find any suggestions or how-to’s for bracing the frame. Can anyone provide insight and/or pictures or diagrams for bracing a 550 frame?

Thanks
FJ 

[hymodyne]

the first suggestion I have read  on this site is to fill in all of the welds that connect the frame. The factory only tacked the ends of some of the seams, so Tig welded seam is a good first step.

hym

[Tim2005]

This article may be of some help to you

http://www.tonyfoale.com/Articles/Frame.mod/KawaMods.htm

cheers

[FunJimmy]

Thanks Tim

That's quite an article.

FJ

[MCRider]

This little CB550F just rocks in the canyons since upgrading the suspension and brakes.  My new concern is that the additional cornering and braking forces are being transferred to the frame and since I’ll be pulling it apart for powder coating this winter, I thought it would be a good time to brace or gusset the frame. I can’t seem to find any suggestions or how-to’s for bracing the frame. Can anyone provide insight and/or pictures or diagrams for bracing a 550 frame?

Thanks
FJ 

Basically, as a lay person, I have gathered that the steering head, backbone to those attached to the backbone, and the swingarm area are the places. Any triangulation you can add provides stiffness. Stiffness usually a good thing, but may expose the next weak link.
here's the swingarm area of my CB750:
The rear backbone to downtube, machinist got carried away. This gusset is larger than intended, the swingarm area gusset is smaller than intended :
The front backbone to downtube area: Since I have a tube removal kit, this gusset will be a bolt on affair straddling the seam between the frame and the removable tube, and triangling down to the downtube.
Nothing on my steering stem as with the CB750 that hasn't been recognized as a priority. On some Kawasakis I remember this being an important spot.

I think HondaMan and Voxonda have made the point that the engine mounts need to be firm and torqued. I hope to use harder bolts and some of Voxonda's reinforced mount plates.

A more comprehensive shot of gussets and gusset area to be.

[bwaller]

Jimmy,

I've deleted a bunch of pics sorry but where the front downtubes are joined and have the three spot welds each is a place that should be welded solid. Any triangulation in the vicinity of the swingarm pivot supports doesn't hurt. The absolute best idea I ever read about was in Gordon Jennings "Gentleman's Express" article in which he suggests a reamed-fit oversize engine mounting bolts to allow the engine to act as a stressed member and help stiffen that swingarm area. I'll be doing this on my race bike.

Check Paulages pics of the race bike he acquired too, it showed some extra frame bracing.

I suppose the truth be known there isn't a huge need for a whole lot of extra help with these frames unless they're roadraced. This was a pretty good offering and especially so if any amount of weight has been removed as in your bikes case.

[MCRider]

Jimmy,

I've deleted a bunch of pics sorry but where the front downtubes are joined and have the three spot welds each is a place that should be welded solid. Any triangulation in the vicinity of the swingarm pivot supports doesn't hurt. The absolute best idea I ever read about was in Gordon Jennings "Gentleman's Express" article in which he suggests a reamed-fit oversize engine mounting bolts to allow the engine to act as a stressed member and help stiffen that swingarm area. I'll be doing this on my race bike.

Check Paulages pics of the race bike he acquired too, it showed some extra frame bracing.

I suppose the truth be known there isn't a huge need for a whole lot of extra help with these frames unless they're roadraced. This was a pretty good offering and especially so if any amount of weight has been removed as in your bikes case.

Got a link or key word to Paulages thread?

[bwaller]

I don't even know how to attach a link......bloody misfit but search "rebirth of a cb550 road racer". I'm sure Paul won't mind. There are a couple pix of steering head gussets.

[FunJimmy]

Thanks Bwaller

I found some of your frame bracing posts from a couple of years ago and you posted photos of the welded front tubes there.
Great photos and advise.

Here is Paulages race bike: http://forums.sohc4.net/index.php?topic=28620.0

[MCRider]

Thanks Bwaller

I found some of your frame bracing posts from a couple of years ago and you posted photos of the welded front tubes there.
Great photos and advise.

Here is Paulages race bike: http://forums.sohc4.net/index.php?topic=28620.0

Thanks!

[SoyBoySigh]

I don't understand the logic behind making all of these changes to the frame without going the sensible route and dropping the engine out the bottom. Ideally, it would make more sense and look better at the same time, to drop out the whole bottom of the frame, and wrap a couple spars along the sides of the engine to compensate. Maybe the bottom hoops could still bolt back in, just to keep the same look. But if something's gotta come out, I sure don't understand making the backbone's the removeable element. That whole section replaced with a cylinder or oval tube section, ala Moko or Egli, maybe. But bolt-out the stock tubes? Seems bass-ackward. Just MY two bits.

-S.

[lucky]

the first suggestion I have read  on this site is to fill in all of the welds that connect the frame. The factory only tacked the ends of some of the seams, so Tig welded seam is a good first step.

hym

The factory knew what they were doing trust me.
The frames have lasted 33 years. No problems except corrosion.

When you weld over the welds, the HAZ (heat affected zones where the metal has been degraded is just further weakened by all the heat. Remember the frame is 1/16 thickness and 33 years old. The less welding you do on it the better off it will be.
That is why when it is welded together the amount of welding and the placement of the welds has been carefully considered.

[lucky]

I don't understand the logic behind making all of these changes to the frame without going the sensible route and dropping the engine out the bottom. Ideally, it would make more sense and look better at the same time, to drop out the whole bottom of the frame, and wrap a couple spars along the sides of the engine to compensate. Maybe the bottom hoops could still bolt back in, just to keep the same look. But if something's gotta come out, I sure don't understand making the backbone's the removeable element. That whole section replaced with a cylinder or oval tube section, ala Moko or Egli, maybe. But bolt-out the stock tubes? Seems bass-ackward. Just MY two bits.

-S.

You should study the history of motorcycle frames before making these kind of statements  The Honda CB750 was not designed or intended to use the engine as a stressed member of the frame.
Double loop cradle frames were a major advancement in motorcycle design.
They were also easy to work on. Very practical.

The modern sport bike frames have the frame all wrapped around the engine
making it very difficult to work on or see what is going on.

[Retro Rocket]

the first suggestion I have read  on this site is to fill in all of the welds that connect the frame. The factory only tacked the ends of some of the seams, so Tig welded seam is a good first step.

hym

The factory knew what they were doing trust me.
The frames have lasted 33 years. No problems except corrosion.

When you weld over the welds, the HAZ (heat affected zones where the metal has been degraded is just further weakened by all the heat. Remember the frame is 1/16 thickness and 33 years old. The less welding you do on it the better off it will be.
That is why when it is welded together the amount of welding and the placement of the welds has been carefully considered.

Lucky, its commonly known that these frames benefit from bracing mate, i have been bracing mine for 30 years with no problems and most if not all the guys that race these bikes brace the frames.

[Don R]

I don't understand the logic behind making all of these changes to the frame without going the sensible route and dropping the engine out the bottom. Ideally, it would make more sense and look better at the same time, to drop out the whole bottom of the frame, and wrap a couple spars along the sides of the engine to compensate. Maybe the bottom hoops could still bolt back in, just to keep the same look. But if something's gotta come out, I sure don't understand making the backbone's the removeable element. That whole section replaced with a cylinder or oval tube section, ala Moko or Egli, maybe. But bolt-out the stock tubes? Seems bass-ackward. Just MY two bits.

-S.

The point is to remove the rocker cover without removing the engine. these tubes were routinely hacked out years ago and left out. Not saying it's a good idea but they didn't seem to fall apart and some of them were bad azz fast.

[scottly]

Remember the frame is 1/16 thickness

My Seeley frame is made from Reynolds 531, and is about 1/16" thick. The stock Honda frame was made out of much thicker, mild steel tubing, mig-welded in a mass production environment. It was designed more with regards to cost and ease of manufacture than rigidity, and can, indeed, be improved upon...   

[lucky]

Remember the frame is 1/16 thickness

My Seeley frame is made from Reynolds 531, and is about 1/16" thick. The stock Honda frame was made out of much thicker, mild steel tubing, mig-welded in a mass production environment. It was designed more with regards to cost and ease of manufacture than rigidity, and can, indeed, be improved upon...

I have measured the CB750 frame tubing and it is .063 thousandths.
They did not have MIG welding at that time. It did not exist yet.
The CB750 frame was welded with SMAW(stick welding).
You can see some of the welding spatter on some of the frames.
Consider those plug welds in those oval punched holes. just as if a bolt was in the hole.

I am a certified welder and a certified welding inspector.

[lucky]

the first suggestion I have read  on this site is to fill in all of the welds that connect the frame. The factory only tacked the ends of some of the seams, so Tig welded seam is a good first step.

hym

The factory knew what they were doing trust me.
The frames have lasted 33 years. No problems except corrosion.

When you weld over the welds, the HAZ (heat affected zones where the metal has been degraded is just further weakened by all the heat. Remember the frame is 1/16 thickness and 33 years old. The less welding you do on it the better off it will be.
That is why when it is welded together the amount of welding and the placement of the welds has been carefully considered.

Lucky, its commonly known that these frames benefit from bracing mate, i have been bracing mine for 30 years with no problems and most if not all the guys that race these bikes brace the frames.

I did not say that you cannot brace the frame, or that it would not benefit, but if it is not done properly by a qualified welder the overall result could be negative.

[dave500]

im still trying to fathom soyboysighs reply??i tried a few beers and it still didnt help,,,,,

[fastbroshi]

I have measured the CB750 frame tubing and it is .063 thousandths.
They did not have MIG welding at that time. It did not exist yet.
The CB750 frame was welded with SMAW(stick welding).
You can see some of the welding spatter on some of the frames.

I'm not so sure about that Lucky.  MIG welding was invented so far back, it's hard to believe Honda didn't have it at that time on their production lines, either in semi-robotic or human directed form.   I'm not a registered welder, but I've worked in an autobody shop and I've personally gotten spatter on me from a MIG.

[bwaller]

im still trying to fathom soyboysighs reply??i tried a few beers and it still didnt help,,,,,

  Well Dave some things are just difficult to comprehend, and if a few beers doesn't provide clarity, it's probably not worth losing sleep over. 

[Greggo]

im still trying to fathom soyboysighs reply??i tried a few beers and it still didnt help,,,,,

At least he didn't write us a novel this time

[scottly]

They did not have MIG welding at that time.

I am a certified welder and a certified welding inspector.

Well, I learned to MIG weld in 1969, in my high school metal shop, on an old Hobart machine (it was a HUGE monster!!).

http://en.wikipedia.org/wiki/Mig_welding

[Mtmooradian]

Mig welding has been around since the 30s, and if it's ok for my Ducati then it's probally ok for your cb. I would love to TIG everything.... But that would be stupid. The type of tubing in the cb won't benefit from TIG, hell I'll braze you a frame together with coat hangers and some hand soap if you want....... And if lucky wants to "inspect" it for me, I'll be glad to send it his way.

[Mtmooradian]

Honda didn't "finish" the welds on the head tube for good reason... All frames flex.... The area that are not welded are there to allow flex.... If they are welded 100% then you've given the frame no where to release the energy. Usually resulting in cracks at the weakest area(tubes)