SF frame fix

chrisk

chrisk

Hero member
Location
Brisbane, Australia
I have an SF frame that has snapped the top rear engine mount. It has snapped right through the middle of the hole.
Is there a preferred way of fixing it? There isn't a lot of meat left on the 'crescent piece' that has snapped off.

I was thinking of cutting off the remaining half hole, making up a new section (complete with hole) and welding in the new section. Thoughts?
 
Without seeing it, it's hard to judge. My approach with broken brackets if I can't replace the whole piece, is to make an overlapping piece which goes back to the closest frame tube. Weld it in as a double thickness.
In your case, You'd have to add material to the original to accomodate the hole.

My experience has been gained in prepping well aged Japanese frames for post classic racing. Not fun, but interesting.
 
I will take a picture tomorrow and post it here.

Meanwhile, I bought a nice Martin box section swingarm for this frame today. Pretty chuffed, it is 4mm narrower than the SF frame at the pivot. And uses a 16mm pivot axle, the SF is 14mm. Easy fix and fitment coming up, if it clears the rear peg mounts that is.
 
You won't have any probs clearing the rear pegs I don't reckon. My Honda alloy swinger is VERY wide and it has workable clearance to the muffler bracket I've fitted to the pillion peg mount - not a lot, but enough. Don't think I could fit the 10mm nut ands std pillion peg tho.
I made a thick metal plate as Greg suggested and had it welded on top of my cracked originals - looks very strong. Excuse the mess - wiring in progress and frame not yet painted!
 

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Guessing the Bike was dropped hard at one time ?

Don't get me wrong all Breganzies fall over like a sheep with Dropsy - Even when when Parked.

I eventually took pride in the Gas Tank Dent from the Bars ;o)

You will need rulers to ensure to Frame is not warped.
 
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I would be worried about not getting a new bit in the exact same spot if you cut it off and started again. But I tend to overthink stuff.
 
Not dropped, not a loose bolt - eventually vibration and km has caused mine to crack (maybe the 270 crank altered the frequency and zone of vibes too?). The originals are pretty (too) thin and the bend to profile it has obviously weakened it. For the extra 50 grams i'm happy to live in the knowledge it's rigid! And it is an integral part of the whole swingarm support structure. Had a mate whose SF2 broke all four lower mounts off near Ceduna!! Motor was hanging by the two top studs. Onto a truck to Melbourne and he onto the back of my trusty SF1.

I made a jig that holds all mounts in place on the frame. But you can fit the motor (empty cases, barrels, head, top cover) and use this as your jig for tacking. Not a tricky job.

Thought you were making an Egli type backbone frame for the new spesh, Chris?
 
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