frame cutting question

[modifiedamerican]

i have a kz750, and im thinking about cutting off some on the frame to make it short. my gut tells me to weld in a brace. but ive seen pictures of cafes, brats where they just cut it and leave like the rugged end look. my question is does it need a brace, or no. heres where i would be cutting it. thanks everyone

 

[rhavindog]

at the very least weld a brace in between and just behind the shock mounts, there is a lot of force transferred into those mounts and not all of it is linear. when youre turningl, especially in a panic turn or veering stop (like if someone pulls out in front of you). you can still leave it rough cut at the end, but put a cross tube in.

 

[AlphaDogChoppers]

As much frame flex as those things have without modification, if you were to chop off the back without substantially bracing it, you would be building a death trap.

 

[Frog]

The original piece has two braces, your back end will be under dangerous amounts of stress, if you do not want to weld you could run some tubing across the rear shockers with threaded rod running through the centre and shock mounts, although it would take five minutes to weld at your local engineers once you've made a brace up.

 

[AlphaDogChoppers]

A mechanical brace that is not welded would NOT be sufficiently rigid, IMO.

It isn't just a matter of mechanical strength. It is all about preventing frame flex under cornering conditions. The original frame before modification already handles like it has a hinge in the middle. If anything, the frame needs to be made stronger than stock.

 

[crazypj]

I would never cut it that far forward, slightly to the rear of vertical line through axle will give a better look.
Probably cut behind seat mounting point and use the welded stand offs as a temporary mount for brace (not good but better than nothing)
You will need to weld in some bracing.
Running anything directly across shock mounts will be even more dangerous, when the wheel hits it, it could stop turning rather quickly or slice up the tyre (or both ;D )
In my experience, a lot of the 70's Kawasaki frames flexed real bad at swing arm pivot and the swing arm itself (you can get a KH400 wheel to touch shock because back end is so flexible)

 

[AlphaDogChoppers]

I have a KZ750 which I acquired recently. I plan to do all kinds of reinforcement where ever I can detect flex.

 

[teazer]

I'd leave the back end stock and add a brace close to the shocks as well.

The stock frame has a place to hand fenders and seat and the tail light. needs the right seat to make it work though. How about a Z1 style with cut doen superbike looking foam.