Seven Fifty cafe-racer. Frame.

In my previous post about Honda CB750 cafe-racer project I mentioned  that I had to do some works with frame, therefore  this part of the story is about these works.

Sure, all that was done might be mentioned very briefly: cutting, welding, grinding, sandpapering. But some key points  may be of interest so let’s take a close look at them.

Firstly, all brackets and mounts that I made earlier and which were welded to frame only point-wise, were welded properly.

Tail tube was welded to the frame and I had a round of cutting, grinding and sandpapering.  By the way I removed remains of all that was earlier attached to sub-frame by  Honda, but found no use in my project.

As one may notice from my earlier posts, I had intention to use old tank mounting points as a mounts for  wiring and cables holders.  For this purpose I converted a couple of nuts into thread sleeves and modified old mounts to fit them.

After welding, grinding and sandpapering they looked quite OEM:-)

I also made a couple of new brackets, like this one for battery box mounting.

Or this one to which, according to my design, intake pipes should be mounted.

As you may see from photos above, nuts were welded in places that are  difficult for wrench operating.

My last task in frame works was design of the plate for tail mounting. I cut it form 2mm plate and then it was welded from both sides on its place and then I drilled it.

I like how that welding looks.

And it could be the end of story if I didn’t find yet another interesting feature of CB750 Seven Fifty frame, which was unnoticed before. The whole frame of RC42 is an example of total asymmetry, and while bike is assembled it is hard to detect that the left shock absorber is set to the left for 5mm farther than the right shock – to right. But on bare frame it became obvious. To be honest, I detected this mischief of Honda engineers some time ago and  took it to mind to check later may it do any harm when non-original swingarm installed. But I had so lot to think about that this curios fact slept out of my mind.

On photo below you may see difference,  the only thing: when I shot this photos frame was turned upside down.

  But now was time to check and fix this issue. Simple measurement showed that yes, it might  cause a problem as left shock turned out to stand askew in relation to right shock. Thus, there was no other way but to shorten left shock mount.

It was a work requiring some precision and accuracy, but I used to apply both, so it was only the matter of time cause in rush one may easily inflict unnecessary harm to part and spent more time to fix it. After some time I found result of my work sufficient and as a final touch completely replicated original design of shock mount. That how untouched right mount looks:

And this is shortened left shock mount:

Thus work on frame was mostly finished.

And in final touch for all these frame works I made the cross-plate in central part of frame also symmetrical. You may call it a kind of engineer protest:-)

Now frame is ready to be prepared for sandblasting and give to paint-shop.

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