If you're new to the sportbike world, you may not now what an undertail is. That's ok - we won't tell. But take a look at your stock bike. Typically you'll have some plain dull black plastic hanging way down over the rear wheel, holding an ugly tail light and a totally legal but butt-ugly holder for your license plate and rear turn signals.
All of that has to go! Yep - the aftermarket manufacturers will help you to chop all that off, re-locate your rear turn signals, and make the ass of your bike look like a work of art. The piece of plastic that you'll install will hold your plate and signals and will really improve overall appearance. But before you spend $200 to $300 on one of these, you deserve to know what you're getting yourself into. This is not just a "plug-in" mod. This is a mod that can easily consume one or two days of your time, and does take some special tools and wiring / soldering skills. So before you buy, make sure this is something you are really willing to do.
Finally, you need to know that no undertail in existence is street legal. The main problem is that NO undertail will have turn signals that pass the DOT specification:
"turn signals must be at least 3.5" in diameter...the license plate must be mounted horizontally, and be illuminated to be easily visible at night.".
You have to consider this before buying an undertail, because it means that you'll have to save and reinstall your STOCK turn signals, and possibly your license holder and light, every time you take the bike for state inspection.
As if that were not enough, be aware that the brake lights and turn signals on every undertail I've ever seen are horribly unsafe. They are too small, and more importantly way too dim to be keep you safe. In noonday sun, the lights on most undertails are invisible. So once you install your undertail, you'll have to start looking for some replacement lights that will get you back to stock levels of safety.
Finally, the instructions for most undertails are just awful. If you've never done any bike wiring or plastic cutting before, don't count on a detailed instruction set to get you through this. In fact, the HORRIBLE instructions provided with my Mototeck undertail in 2002 were the primary reason I decided to post this entire web site - to make my own instruction set to help out the other guys. I'm not convinced that any other manufacturer does any better. They assume you are a master electrician and a body shop veteran.
When you put all of this together, installing an undertail doesn't sound like a very rational thing then, does it? Here are my summary thoughts below:
| Undertail | Stock | |
| Physical appearance | great! | bad |
| Cost | $300 | FREE |
| Pass Inspection? | NO | YES |
| Time to install | 1 to 2 days | None |
| Safe? | No - must replace all lights | YES |
Would I install an undertail if I'd known all this in the beginning? No. But if you're a guy who loves to do his own handiwork on the bike, if you're a guy who loves tearing the bike apart and putting it together again, and most of all if you don't mind doing this every two years for your state inspection, then get an undertail. If you'd really like to ride your bike rather than work on it, I'd suggest getting a "fender eliminator", which you can make yourself for a few dollars. That way you still use your (DOT legal) turn signals and you'll have to do NOTHING when it comes time for state inspection.
An undertail really does translate into $300 for a world of headaches, for a small cosmetic improvement.
No money for an undertail? Well, there are some other options. You can save a LOT of money, in some cases stay LEGAL, and still get rid of that ugly stock fender. There are 3 good choices:
In case TAZ's excellent how-to goes off line, you can download a .pdf version to save. Be sure to send TAZ a thank-you note for all the work he's done on his web page ! 
In my case, I installed the Mototeck undertail, then replaced every light, and ended up with a nice-looking result. And I rode like this for 5 years, until my first state inspection was due. Then I found out there was just NO WAY that I was ever going to pass my state inspection with this setup. In Delaware at least, they give you no choice at all. The plate has to be horizontal, and the tail lights have to be 3.5" diameter minimum - and that means that you're going to have to RE-install the stock tail lights.
So here is my solution. I kept the undertail, but I removed the amber lights, and filled the holes with Bondo. Then I made a TAZ fender eliminator and painted it white with several layers of clearcoat. I installed the fender eliminator underneath the undertail, and you can see the result at right (click for larger view).
I installed the fender eliminator underneath the undertail, and you can see the result at right (click for larger view).
This result is totally street legal. It is not quite as cool as my pure undertail look, shown above (with the vertical license plate). But at least I can get through state inspection now. All I have to do is to change my exhaust back to stock every two years.
Click for larger views.
To see a few more pics and discussion, see the discussion on the TAZ mount.. And remember, you can get great instructions on how to construct this "TAZmount" at Maxlean.com, or if the site is down, download the instruction set here.
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You can download my entire instruction document [1.5MB] and print it out to take out to the garage with you. It will show you how to cut the tail, and get all the wiring done. All undertails that I've seen require some trimming of the trunk section.
Here's what your tail should look like after you've trimmed it. You'll only lose about 1.5 inches in the depth of the trunk. Mototeck doesn't tell you that you'll have to make circular cut-outs in order for the tail lights to peek through. But if you don't do this, you'll never get the undertail to fit in place.
On the right is the view looking down into the trunk , with the undertail installed. You can see how the tail lights have to "peek through".
Here is what you'll cut off - the entire fender - in order to install any undertail. This is best done with a Dremmel© tool and #9011 rotary saw bit. But keep the turn signals - you're going to need them the next time you go through state inspection!
For the wiring connections, click on the thumbnail image at right
I won't go into a lot of further details here, because it is all shown in explicit detail on my downloadable Mototeck instruction file.
I've kept this section for historical reasons - Texas Fairing is no longer with us. But I'd still recommend taking a look at the very complete how-to at TAZ's web page, because it will show you just about the same steps that I went through with Mototeck. In fact, for any brand of undertail the basic process is the same.
The original Mototeck undertail was a great example of how NOT to make effective turn signals. The tail was supplied with a set of 5 (five!) watt incandescent bulbs. It's impossible to imagine how anyone could make such a product, knowing that a rider's life was depending upon those lights.
With other undertails, I haven't seen anything that would be much better - lots of them will make pretty LED arrangements, but in daylight (and even at night) these are just about invisible.
So if you've installed an undertail, take a good look at your turn signals. Then take a good look at your turn signals in NOONday sun, and try to imagine your an 85-year old lady with 20-300 vision with cataracts, who accidentally forgot her glasses, is now driving a '73 Buick, and following you. Are you betting your life on those feeble signals? If you've got any sense, make sure to replace those lights before you get that undertail out of the garage. It's easy to do.
Here are those feeble 5W turn signal lights that came on the undertail. Absolutely horrible. The tail lights were not any better - so all of them had to be replaced. Compare the photos with the lights on and off - there's not much difference. You sure don't see any blinding glare, in fact even when you're looking directly at the turn signal, it's difficult to tell that the light is on.
First, read about LED 1157 replacement bulbs for those tail lights. The ones at Superbrightleds.com© are the best that I've found. Get the largest that you think will fit in the housing.
Second, throw away the turn signals entirely - housings and all. You can shop around for replacement turn signals. For my tail, the best replacement were a set of Lockhart-Phillips 4 single-filament amber flushmount lights, which I got at Ridegear.com for $15. You'll have to enlarge the holes in the undertail to allow these to fit, but that is easily accomplished with a Dremmel tool and #9011 rotary saw bit. Then the LP4's just screw in. They make great replacement turn signals. The size you want is 2-1/2" X 1-9/16" . This is still not large enough to be street legal (the requirement is 3.5" diameter), but is large enough to be safe, and is ten times better than what comes on most undertails, including Mototeck. Enlarge the image at right to see more detail on the turn signal replacement.
Here is a photo of the LP4 inserted on the left of the image, the stock Mototeck light still on the right. The LP4 makes a perfectly sized replacement for the contoured area of plastic. Note the LP4 carries a 21W bulb - the same wattage as the Suzuki stock turn signals, and it is my opinion that they are just as bright. However, these LP4 will not satisfy DOT requirements that all turn signals be 3.5" or larger. So you may have to somehow rig up your Suzuki stock signals when you go to get inspected.
Here's the appearance with both Mototeck lights replaced by LP4's. It's a good fit.
A friend of mine, Badkarma, installed a Texas Fairing undertail. It's a nice undertail, but also came with very weak lights. He installed a set of LP5 lights as replacements. They just stick on with adhesive, so there is no drilling required at all. The result is a good cosmetic fit, although of course these are even smaller than the LP4's that I used, and therefore these are not street legal either.