I guess I could change the first post to say that if you have the money, have your forks done professionally. If not, here's a cheap way that will work. I dont work on bikes professionally and I dont know it all. I wrote this article with the help of a few others that have built forks for some pretty quick bikes.
There is a right way and a wrong way and any way that damages parts is the wrong way.
Pipe wrenches will scar up aluminium. It will not crush the pipes because pipe wreches dont work that way. They grip only enough to hold. Where you hold on to the rod will be under the lowering spacer and will not travel through the bushing.
I own and have used pipe wrenches (but not on fork internals). I have also disassembled the cartridges so I am very familiar with the amount of force required to remove the cartridge head from the cylinder. Kayaba uses some type of epoxy on them as residue on the threads is white. Trust me, if you were to run a bore gauge through the sections of the cylinder where you grabbed it with the pipe wrench you will see it is no longer round.
While you are correct that the marred up end of the damping rod will not come in contact with the bushing in the cartridge head while the spacer is there what happens if you have to put it back to stock?
It would be one thing if there was no other way to do it, but Race Tech sells a shaft holding tool for that purpose. They also sell a cartridge holding tool for cartridge disassembly so that you do not damage the cylinder.
I'm not %100 sure what you're talking about. The cut fork should bottom out the same as an uncut fork?
They bottom out the same but you have reduced the range of travel. About half the time that fork is moving it is much harsher than it needs to be. There a couple of options to change this. There are two methods that are free and will improve the forks function. There is another option that requires you buy some parts, but IMO offers a much better solution.
The preload will be the same, if you remove the same amount of the lowering spacer from the stock spacer.
OK then, what is the base preload on a stock set of forks?
When you set up a set of forks you install the springs with a base preload on the springs, usually 10 or 15 mm (unless you are working with Ohlins stuff).
Yeah, the stock springs are light. Adding a heavy spring, especially for us big guys, is not a bad idea.
You can accomplish close to the same result by adding more preload. Though you can't add too much preload or you'll bind up the spring...
You shouldn't be binding the spring up. If you are worried about binding up the spring then I would suggest running a stiffer rate spring than you would normally run but installing it with less base preload.
You are correct on the shim stack or oil height, I have not idea what you're talking about. If you want to share some knowledge, please do! As far as bleeding the air, what do you suggest? This way seem to work well for me and countless others.
To bleed the cartridge you want to install the cartridge (using a different type of cartridge holding tool to hold the cartridge while you torque it) with the damping rod installed and no spring. I open up the compression adjuster all the way and pour some fork oil in, usually about 150mm from the top of the outer fork tube. I work the damping rod up and down several times and then let drop in all the way. I then extend the fork a little longer than its normal fully extended length, put my hand tightly over the top to seal it and then push down on the fork. This pushes the oil through the cartridge. Once I do that several times I then install a bleeder tool on the damping rod and work it up and down until I no longer see any air bubbles. It takes a long time to bleed the air out.
I then use a fork oil height tool to set the height as this is something you can tune with. Oil height is dependent on what type of valving you are running and somewhat of a personal preference. Depending on the set up and the rider's class I usually start a new rider out with 130mm to 120mm and then experiment from there.
Remember, the space left in the fork by the oil acts as a progressive spring. The higher the oil level, the stiffer it gets as the fork compresses.
Also, that Bel-Ray 20wt fork oil is thick as hell. They run that damper rod forks.
What can I say? When you're working in a hot garage, you'll do anything to get it done! If you'll notice the 2"ers we took out were machined sleeves that I put in there the first time...
Metal on metal wear creates particles that contaminates the oil which wears the valve faces and shims.
Personally I would machine up spacers made of Delrin and install them with a washer at the spring end. And if anyone thinks the Delrin is no good, Ohlins uses Delrin spacers to adjust fork length in all of their Superbike, new style R&T forks, and Superbike Cartridges.
I know that you are not going for handling when doing this mod, but you can make changes to so that it improves the ride quality. I can only imagine how rough that front end feels. In the end you want the forks to move as smoothly as possible. If you look at the forks you will see other things that need to be addressed to make them work correctly.
You want everything super clean as you do not want to contaminate the oil.
These guys here -
http://www.dirtrider.com/tech/141_0806_race_tech_fork_rebuild_secrets/index.htmlare servicing a set of dirbike forks. While Busa forks do not have all the parts they have, you can see some of the tools they and methods they are using.