ArBrnSnpr
Been Around the Block
Hello all,
I'm in the process of reworking the rear subframe on a 81' CB750f to remove the "DOHC" hump. I've already removed the factory tubing, bent a new top tube and partial "legs" I guess you could call them. I have it all sitting on the bike now and I'm tossing around ideas to replace the factory rear shock mounts.
I intend to leave the mounts in the OEM location so as to not mess with the geometry of the bike too much while still accomplishing my goal.
I've considered a few options so far:
1: Re-angle the factory mounts I cut off, then re weld them as gussets/mounts back into my new frame.
Pros: It's quick, easy, cheap.
Cons: The mounts feel weak, the threaded portions are old and could potentially strip, I dislike the acorn nut
2: Box in a new angled mount as a "gusset", drill a hole through it and run a section of M10x1.25 internally threaded rod though both sides, sleeve the middle, then run a bolt through the back that is short enough to allow a bolt to not bottom out that would be coming from the outboard side and holding the shock on. The bolt from the back would be ground flat and welded into the threaded tube for added strength.
Pros: Cleaner than factory, ability to use new grade 8 hardware, should be stronger than stock with the right material thickness.
Cons: Time consuming, additional cost.
3: Same as above, but use a solid rod instead of threaded tube, then drill and tap and insert for the shock retaining bolt.
Pros: Possibly stronger than option 3 ...?
Cons: See above.
4: Use a solid piece of steel and cut a piece that will fit between where the tubing meets, weld that in. Drill a hold for either a threaded rod, or tapped solid tube.
Pros: Increased strength over boxed steel...?
Cons: HEAVY!
Here's a pic of what I'm working with
And zoomed out for context
Thanks!
I'm in the process of reworking the rear subframe on a 81' CB750f to remove the "DOHC" hump. I've already removed the factory tubing, bent a new top tube and partial "legs" I guess you could call them. I have it all sitting on the bike now and I'm tossing around ideas to replace the factory rear shock mounts.
I intend to leave the mounts in the OEM location so as to not mess with the geometry of the bike too much while still accomplishing my goal.
I've considered a few options so far:
1: Re-angle the factory mounts I cut off, then re weld them as gussets/mounts back into my new frame.
Pros: It's quick, easy, cheap.
Cons: The mounts feel weak, the threaded portions are old and could potentially strip, I dislike the acorn nut
2: Box in a new angled mount as a "gusset", drill a hole through it and run a section of M10x1.25 internally threaded rod though both sides, sleeve the middle, then run a bolt through the back that is short enough to allow a bolt to not bottom out that would be coming from the outboard side and holding the shock on. The bolt from the back would be ground flat and welded into the threaded tube for added strength.
Pros: Cleaner than factory, ability to use new grade 8 hardware, should be stronger than stock with the right material thickness.
Cons: Time consuming, additional cost.
3: Same as above, but use a solid rod instead of threaded tube, then drill and tap and insert for the shock retaining bolt.
Pros: Possibly stronger than option 3 ...?
Cons: See above.
4: Use a solid piece of steel and cut a piece that will fit between where the tubing meets, weld that in. Drill a hold for either a threaded rod, or tapped solid tube.
Pros: Increased strength over boxed steel...?
Cons: HEAVY!
Here's a pic of what I'm working with
And zoomed out for context
Thanks!
