Shortening forks by modifying the internals is usually done to long travel dirt forks to adapt for street use, and the travel is decreased by the amount the forks are shortened. If it is done to a street fork as much as half its travel will be removed, leaving too little travel for proper suspension action. More properly the stantion tubes can be shortened by cutting the tops down and remachining for the top caps. The spring will have to be cut down as well which will increase the rate, so hopefully that will not be a problem.
Why so much shorter? Your ground and cornering clearances will be decreased, and unless you lower the the rear by the same amount the rake and trail will be decreased which can adversely effect stability.
I take it you slid the forks down to get the look you are shooting for, which explains why they "look fine" in the picture. One more thing you need to do to the springs: the original top of the spring has the last coil shorted to get a flat surface to bear against the top cap. If the spring is left as you see it in the picture when it compresses it will bend, causing a bind against the insides of the station tubes. To prevent this heat the top coil and bend it down until it contacts the coil below it, then grind it flat preferably with a disc sanding wheel. It must present a surface as exactly perpendicular to the spring as possible to prevent deflection.I need it shorter only because the stock clip-ons were ABOVE the triple-clamp, and the new Woodcraft clip-ons I am installing are going BELOW the triple-clamp. This is a cafe-racer FJ1200 I am putting together, and the original bar position was really high and relaxed.
The tubes sticking up past the triple clamp didn't look right at all. I have to keep this under a budget of $500 and I am cutting every corner that is still safe. I have no problem with cutting the fork springs.
Here's the build thread http://www.fjowners.com/index.php?topic=11779.0
I hope you can find a machine shop that can handle single pointing threads on the inside of the tubes for the caps without charging an arm and a leg. At least I think it will have to be threaded from the picture.
Shortening a fork by cutting the spring only is a common custom builder method when working on a show bike that will not see much street use -- it gives the right look, but creates several problems. First, cutting the spring effectively eliminates two inches of travel of the fork right from the git go. Sit down on the bike, and another 1" to 1 1/4" is used up, leaving only 1 1/2" to 1 1/4" of travel to deal with bumps, braking, landing from wheelies, and all sorts of unpredictable happenings while riding. The forks will be bottoming out a lot, and that can be a very bad thing, resulting in damaged bearings and fork seals. All that may be bad enough, but pales to insignificance when compared to the badness that can happen when cornering: with the suspension already down to its last inch of travel, unless the corner is billiard table smooth the slightest bump midcorner will bottom the fork, slide the tire, and cause a goodly crash.Can you explain further what you are referring to here? I did grind the spring ends flat before final assembly yesterday.
Not sure what you thnk might need machining - Everything is back together as it should be. I appreciate your info, though.