Why so many different Kohler regulators/rectifiers?

In a previous post I asked for and received help on locating the regulator/rectifier for my Kohler engine (MODEL: KT730, SPEC NO. KT730-3012). I found that the alternator/stator was generating (at the plug) a maximum of 44 volts AC. But the regulator/rectifier was not outputting 12V DC.

The defective regulator/rectifier had the number 25 403 35 1916 which I was NOT able to find on the internet anywhere.

After some time, on kohlerenginesparts.com I was able to locate the schematic for the part with the following information: 25 403 35-S REGULATOR/RECTIFIER 12/15A HALF-WAVE STD $12.40. I was then able to locate this part in one of two offerings on eBay.

All of this prompts several questions.

1. Why are there so many different regulators/rectifiers for Kohler engines?
2. Why does Kohler make so many different engines within the same horsepower rating?
3. Why does the kohlerenginesparts.com NOT allow new users? They only allow for “Existing users.” I’m under the impression that it may be only for dealers. See attached screenshot.

My particular engine appears to be some type of odd-lot; otherwise, why the difficulty in locating such a common part?

Kohler make their engines according to what the end user specify.
Mowers are the same as cars, the people who buy them have less than no idea how to evaluate them and continually expect new and better models, when in fact they all get worse.
The easiest way to impress Mr Stupid is to put a bigger motor in every couple of years so they want a 20hp one year then a 20.5 next years then a 21 the years after and so on till the model gets replaced with a new one.

As for rectifriers, they get bought in so are a cost . They range from a single diode as still fitted to a Briggs dual circuit ( cheap & nasty ) through to full wave inverted & regulated best but most expensive.
So you the end customer gets what the mower factory orders and you have to remember the buying public are so stupid they almost always buy the cheapest mower in each deck width.
So if Husqvarna can fit an engine that is $ 1 cheaper than MTD they will sell twice an many mowers that season.

So next season MTD demand a bigger Hp engine cheaper than last year and one way to make it cheaper is to fit a lower capacity alternator with a cheaper rectifier.
If it boils your battery then tough luck because there is no such thing as brand loyality any more.

Strait full wave rectifiers are interchangable so you can fit a $ 10 radio shack one if you know how to wire it in.
Regulated ones are a bit more tricky because they have to be matched to the output of the alternator otherwise they have difficulty turning the alternator on & off as the battery voltage changes & mower load changes.

As for the web page, I think that is an old site, it is not the Kohler site that I get IPL's and manuals from.
There are a lot of phantom sites on the web that were abandoned by their owners a long time ago but still exist of mirror servers till till that one is replaced and the new one is reloaded.
A lot of cheap host companies just get bigger & bigger servers and when they get a new one they do a bulk transfer from the old one because it takes a lot of time to go through & weed out all of the old stuff.
Other companies leave the old stuff up there as an archive but restrict access to it because they want you to buy new product.

The page that you link is the current customer purchase website for Kohler. If you start the purchase process by putting in your zip code, and then shop for what you want and then start the checkout process, it will give you the option for new customers.

bertsmobile1,

Hello in Australia! Thank you for your very detailed explanation. You made my day! Beginning with "Mr Stupid" I was laughing all the way through the post. I know what you mean. I have a 2005 Cub Cadet SuperLT 1554 which has a heavier deck and frame than the new models almost identical to it. Furthermore, when my old 27hp Kohler engine gave out, I installed a 5.5 hp (vertical) Honda engine in its place and pulled my 60" Swisher pull-behind mower for an entire season. I don't pretend to understand the electronics of voltage regulators/rectifiers. I was just curious.

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ILENGINE,

Thank you for your explanation of the Kohler website. I presume that it's the bible for Kohler engine parts. Although I feel that it could be more intuitive (especially if they want to sell parts), once I located my exact engine, I gained all the information that I needed. I found it interesting that a person cannot print out the data page

Dealers have their own login/password website that they use for parts lookup, service manuals, service bulletins, etc. Up until recently the dealer page could only be used with internet explorer,