Topic: Is this frame bent?

[Stoli]

This is a CB750 '77 Super Sport.



Is this normal for this year/model? All my other bikes are Ks and the back doesn't slope down like this.

[goldarrow]

I don't have a 77 but that looks way off

[754]

Bent..

[Stoli]

That's what I thought but both sides are perfectly symmetrical. How does something like that happen?

Maybe the passenger weighed 500 lbs?

[disco]

Ouch! Likely been rear ended. Definitely bent.

[754]

Or an endo, check the front.
When you eyeball the front downtubes from the side, do they look parallel.

[Stoli]

If it was in an accident, it has been rebuilt since. The rest of the frame looks staight. It rides fine. Little shimmy at around 45 mph but smooth on both sides of that.

[Don R]

 I had a 75, it was similar but it was bent on one side. I put straight edges on it from side to side and had 3 different angles. If you could jig it up somehow that could be straightened, the question is what else is bent. It may have done an endo.

[Retro Rocket]

Or an endo, check the front.
When you eyeball the front downtubes from the side, do they look parallel.

I'm with you on the endo, I certainly wouldn't ride using that frame until it was put on a frame jig and straightened or replaced...

[MoMo]

If there was an endo most likely there would be damage around the steering neck too.  No signs of stress marks around the neck?...Larry

[Retro Rocket]

It would be a bit harder than that to straighten Cal, there is a bend in the rear down tube, the top bend is actually after the shock mount, in front of the rear  down tube, so its not quite that simple mate...

[Garage_guy_chris]

Id say bent too but were forgetting one thing:





Just plain too much weight on the rear extension part of the frame.....

As for fixing it I see the bend in the two rear down tubes too. I think it would require a tear down and some big heat and force to bend back. In the end it may be easier to find a virgin unbent frame, paint it and transfer everything to the new frame

[Retro Rocket]

Seeings though these frames have a weak spot at the swingarm pivot I would be worried about  alignment  there, racers put an X brace above the pivot for strength and to restrict movement, I also wouldn't be surprised if the back engine mount bolts are tight as well, that would have taken a pretty large amount  of force to have done that much damage...

[Stoli]

Thanks to all for the insight.

I just found a replacement frame on eBay. I'm rebuilding this bike for my son, so I'm not going to take any senseless chances. We can't prevent all accidents but it seems to me that riding around on a questionable frame is a risk that can be easily avoided for relatively short money.

[MoMo]

Don't let this guy ride as a passenger on the new frame or you will wind up with the same problem

[SOHC4 Cafe Racer Fan]

Thanks to all for the insight.

I just found a replacement frame on eBay. I'm rebuilding this bike for my son, so I'm not going to take any senseless chances. We can't prevent all accidents but it seems to me that riding around on a questionable frame is a risk that can be easily avoided for relatively short money.

Good call.

[Retro Rocket]

Thanks to all for the insight.

I just found a replacement frame on eBay. I'm rebuilding this bike for my son, so I'm not going to take any senseless chances. We can't prevent all accidents but it seems to me that riding around on a questionable frame is a risk that can be easily avoided for relatively short money.

Good call.

+1