Help with GSXR fork swap.

Hi there. Recently I have taken on the task of swapping a set of 2003 GSXR 750 forks onto my 1982 KZ 750 E3. I got lucky with the GSXR fork because the steering stem bearings are the same for both my KZ and the GSXR. But when I tried to simply bolt up the GSXR triple trees I found that the GSXR steering stem is about ½” short.
After doing some research on KZR I found the most common method for swapping on modern forks was to have a bushing made that will weld on to the old KZ stem and still press into the modern triple. But my KZ 750 steering stem is only 2 or 3 tenths of a mm smaller than the GSXR stem. Too small to press into the GSXR triple, and I imagine it is way to big to have a bushing welded on.
So after doing some more research I came upon something that might work. Simply get a machine shop to make me spacer that I can get welded in the GSXR stem that will increase its length exactly ½”. Here is a picture for reference.

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My question would be, how safe do you guys think this would be and is there anyone here willing to help me out that has access to a machine shop and a welder, I think the stem is made of aluminum. I would be willing to pay someone what ever they think would be a fair price for their services.

I wouldn't do that mod. There's too much at risk - your life, if it fails.

I've designed some aluminum weldments and performed structural analysis in some positions that I've been in over the years, so I know a little bit about what you're playing around with there.

Loading in the area that you propose to cut may be low enough for what your thinking about doing, but your wall thickness in the stem may be problematic with welding there. Welding steel, where if the weld is done properly, results in a joint that is just as strong as the parent material. No so with aluminum. Its strength is lower, and can be one half to a third of the parent material. It's called the heat-affected zone(HAZ). Another problem for you.

Is it possible to take the KZ stem, chuck it in a lathe then turn down the step on the bottom to the same diameter as the stem above it? After that you could have a bushing cut and machined that could be slipped over the end of the stem that was just turned down, then properly welded (a full-penetration weld advised) to the KZ's stem. The outside diameter of the bushing could then be turned down to the correct diameter to provide a proper interference (press) fit between it and the receiving hole on the lower triple clamp. It's not that hard of a mod for a competent machine shop with a good welder on staff. Your best bet would be to take the pieces to a shop that I described and get there opinion on the matter too. And of course, it's your choice and risk no matter what you do. This isn't a bracket that you're playing around with, but a critical component whose failure could be catastrophic. Good luck.

First off I would like to thank you for you fast response. Second I have absolutely zero experience working with aluminum, so you opinion is greatly appreciated. Based on what you said I don’t think I will be having the GSXR stem cut and welded, my safety may be jeopardized by the quality of that weld. Having the KZ stem machined down and a bushing made was my second choice and obviously will be the route I take. It just seemed much easier and cleaner to simply reuse the GSXR stem.

Another option is to make a new stem, it's a common solution.

The stem is/should be steel. The problem you would have with that solution is that the GSXR stem presses in from the bottom, preventing you from simply extending it. A better solution would likely be swapping the Kz stem or making a new stem as steell suggested.

i have done/can do the machine work to convert these trees for you.if you need some help let me know.

leon