Not unthinkable you have hardend spots where they´re best or bulged, can not be mended. They are made by cold forming.  When they crack they crack good, thats aluminiums downside. Steel gives fair warning. But it´s hard to give advice w o seeing parts live of course.

Attempts to straighten bent motorcycle forks were always regarded with a great deal of suspicion when I was riding back in the seventies. The general opinion was ” you can’t bend things straight”.

 

Now making new tubes should be possible, although it will depend what machinery you have. You might want to line bore the internal bore, with a between centres boring bar for instance. If your lathe is not big enough for that, you could use a setup like I used for my steam launch main bearings. I made a boring bar that ran in a pair of pedestal bearings, bolted to a flat table. The engine bedplate was bolted down between them, and by traversing the rotating bar through the bearings the bores were machined. In my case the bar was rotated by an ordinary electric drill. The fine feed for the traverse was arranged by using the table of my mill drill to mount the work, so that by winding the handle on the table the job and the pedestal bearings moved. The drill was held down on a nearby workbench and drove the boring bar via some rubber hose couplings. Very crude, but capable of doing a good job.

 

You would also have the problem  of making sure you had suitable material.

 

regards

John

Posted by John Olsen on 08/09/2010 22:30:29:

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John, if you are talking about the steel fork tubes we used to straighten these all the while and very successfully.

We used to push a piece of plastic waste pipe over them as close a fit as possible given the limited sizes to protect the chrome, then lob them into a big powered set of sheet metal rollers.

 

Start up and let them run giving a tweak at each end every so often until they couldn’t go no further.

Used to take about 10 minutes per leg and because of the rolling action they came out dead straight.

 

There used to be a big pile of them stood against the roller on a Monday morning !!

 

John S.