How to tell you have a straight frame.

[Gcraay]

I bought a 75 and while i have had luck with the engine, the frame has a bend off the ass end. I did plan to cut off the extended seat bars and shorten the seat anyway, but now I'm concerned about the rest of the bike. I see a slight bend in the shock mount area, but that could be cut out as if I were doing a bobber. But, what I am looking for is a way to check for...square. The bike itself is not exactly squared off like a car frame, so...how would you do it? Since the frame may not even be designed off exact degree angels do to clearance for mounting brackets and other things, are there any bends that should be there? The book shows perfect lines, but I know that isn't an exact reference.

I hope this frame isn't a lost cause.

 

[Royboy]

Here is a place to start: http://www.xs650.com/forum/showthread.php?t=64&highlight=frame+dimensions

Search frame dimensions on this forum for other references.

roy

 

[TwoManyXS1Bs]

We had a frame cage, a stiff contraption that you would fit a frame into. Using spacer blocks and clamps, would snug it down so that offending bends could be pryed back into reasonable position. We weren't laser-accurate, just eyeball and tape-measure good enuff to return to service.

Still, not a job to be taken lightly...

 

[XSLeo]

I might measure from fixed points on the frame, like the grease fittings on the swing arm to points on the steering neck. Should be the same from side to side.
Leo

 

[angus67]

could go from spark plug tip to axle plates. That's how I do my chop. I don't have hash marks on my axle plates so that's how I tension my chain, and straighten the wheel. might work here.

 

[fredintoon]

Hi Gcraay,
you could try a road test. Take it for a ride and see how it handles.
Get it up to ~30mph and take your hands off the 'bars.
If it steers straight you have no worries.
If it dives for the ditch or across the road, you got 2 options if you are honest and 3 if you are not.
1) Measure, cut & re-weld the frame.
2) Hang a sidecar on it.
3) Sell it off.

 

[chizler62]

If the frame is naked, then you can put it on a flat surface with swing arm and shocks on. Tie a string from rear axle plate on one side up around middle of the head tube area and back down to the same spot on the other axle plate. You can then install rear wheel and check to see if it runs in the center of the strings.

To check twist lay the frame on its side. Clamp, strap etc so the head tube is parallel to flat surface, ground etc. That Make sure swing arm pivot, rear axle etc is perpendicular to the ground, flat surface.
Once you start doing this you'll notice quickly where its whether its bent, twist or not.

 

[Gcraay]

well, thanks for the tip, but its all apart now. I'm figuring that since all the long pins go in for things like the swing arm and the motor mounts it may be only the tail end where the seat goes. The lower rear set mounts look a bit wonky, but I'll be slicing them of anyway.

I think i'm gonna just cut and rebuild the U at the back.

thanks again.

 

[Gcraay]

Cool thanks, it is just frame right now. I'll try that.