1981 CB750F DOHC - Solid Stamped Subframe?

[jcharny]

I'm just starting on a 81 CB750F brat build and had a quick question. I'm looking to weld on a seat hoop but have heard from a gentleman at dimecity that my year F model may have had a solid stamped subframe. This would prevent me from using slugs to join the frame to the hoop and would make the whole process significantly more complicated for an amateur welder like myself. If this question has been answered before, my apologies- i tried searching and found very little on F models.

Thanks,

JMC

 

[jcharny]

Maybe I should have put more effort into my post... here's exactly what I'm looking at and what I'm trying to achieve. Bellow are two photos of what my frame currently looks like. Following those photos are two I've been using for inspiration- the first a build by Debolex Engineering and the second a build by Steel Bent Customs. Ideally, I'd like the subframe to be the shape in the Debolex build, with a totally flat line leading to a mildly upswept rear. The SBC build appears to maintain the existing subframe structure with the only apparent modification being a tail hoop. I also believe the suspension mount has been moved in the Debolex build while it hasn't in the SBC build. In fact, I think the Debolex build uses a completely new subframe, with enhanced gusseting and new tubing throughout.

Would love to hear some input from y'all on the varying levels of complexity and technical challenges associated with both subframe styles. Is the Debolex style out of the question for a first-time builder? Is the extra work simply not worth it?

JMC

 

[CALfeRacer]

It looks like if you cut the ends off you would have tubes that a slug could be put in. Be aware that with stock suspension the wheel will travel close to the cross bar on the frame, so a flat seat like the second bike would have tire clearance issues. I'd assume that they're talking about the stamped frame design like this:

As far as moving suspension mounts and subframe fabrication, I'd try to leave that to a professional welder if you aren't so great. I know that I wouldn't trust my welds in a high stress application like that. But, if that's really the route you want to take then it can be done, just be aware of the consequences (positive or negative) of altering the suspension geometry.

 

[Bert Jan]

JeeZz.. Thats just regular tubing. Cut the stamped areas witv a grinder and weld the hoop in.

 

[Bert Jan]

Btw, solid stamped does not exist. Its either machined, cast or forged. You cant stamp solid into a perfect round tube. Btw, it would be heavy as f@&ck..