Ok, since this is considered taboo. I'll start.
...this is taboo? Since when?
First, why would it be ok to take apart other pens like: Snorkels, 51s, Vacumatic, etc and not MBs?
Because they can take them apart with little risk or special tools. The Vacumatic is the obvious exception from the pens you listed, and a lot of non-pro repairfolk don't repair their Vacumatics or Sheaffer Plunger fillers.
For most people, $50 is a small price to pay to know that your $300-400 149 isn't going to become a pile of parts. You can't send in a Vacumatic to Parker and have them repair it, let alone for $50.
If your answer is parts, its not a good one.
Parts are a great answer, though there are many.
If I break the piston assembly on my 1960s 149, the only real option would be to ask around for a new one. If I wasn't willing to wait along time, I might end up having to buy a pen with a bum nib for $150-200. On the other hand, if I have a Snorkel with a thrashed filler, I can probably find the parts I need in a $20 donor pen.
And Niksch is right, opening the section from the front and greasing doesn't do anything. You need to remove the piston filler and lubricate it.
I find this hard to believe. I've lubricated the pistons of dozens of pens, and in almost all cases a lubrication from the front does the trick. If it doesn't, then the piston mechanism is ill designed, the seal is too tight. When taking apart a piston filler fully, I may apply some silicone grease to the mechanism's threading but that doesn't do much at all. Perhaps more on the more fragile piston assemblies (MB multi-stage, Conklin Nozac)?
If it's easy to take out the entire mechanism, applying silicone grease directly to the seal and around all of it will indeed give you faster and possibly better results. But I can't say I've *ever* encountered a pen that required such treatment.
I told Richard Binder, at a pen show, the piston was tight on my 146 and he used a special slotted tool he made to remove the front section and put some silicone grease in. It did ABSOLUTELY NOTHING. The piston is still tight. And, of course I paid him for it.
Binder isn't perfect. If you were at a pen show, why didn't you try it out and say "Uhn? This isn't any better." Even if I had mailed it in and gotten it back that way, what most every repairman wants is for you to send it back with an explanation. Contrary to what some folks may think, Binder isn't the be-all-end-all- he's a regular guy who might not get it on the first try, or he may not have understood your complaint.
I have a number of pens I'd like to work on and would rather not go to MB for $50-$65 a pop when I can probably do it myself. I am particularly interested in the 146 and 149, but add your info as well.
Don't let us stop you! Sounds to me that you have a good handle on it- have at it.
Tutorials would be great. I, myself, and I'm sure others would be willing to pay for any type of education on these pens as well.
If possible could we keep this discussion centered on How to, rather than a debate on whether or not it is ok to take a MB apart.
I don't think many folks claim that it isn't "ok" to take a MB apart. They just recommend not doing it if you don't know what you're doing. Why? Because no one wants to end up with a bunch of angry emails or all-caps FPN posts telling them that they ruined their pen. Especially when you're talking about a $200-500 146 or 149.
Which has a lot to do with why a lot of amateur knowledge doesn't exist on how to disassemble them- self-taught folks usually learn by doing, which entails a lot of learn by screwing up. If you want to break a few $300 149s before finding your bearings please do- and make sure to write up the details for all of us, k?
If you do decide to go that route, please get a lot of practice before advertising as a MB repairman. Some folks have done a repair a few times and call it good; I've a pile of broken pens that would disagree. Some of them were broken by myself in the course of learning; others were broken by folks who claimed to know what they were doing.
Bottom line is that some of us have pens that we like to much or cost too much to risk breaking. I've replaced cork piston seals on a 15-20 different pens (not many!) and feel comfortable enough doing so. But did I try to ham fist my semi-sumgai Oversize Conklin Nozac? Hell no! That went straight to a pro, even though it wouldn't have represented a huge loss of outlay if I did break something.