Thruxton mods: FEK and flashers

You may think I’m obsessed. It’s true, I’m obsessed. It’s been a really, really long time since I had fun wrenching on a vehicle. I think the last time I actually had fun working on my car, I mean really working on it, was my first Toyota truck (a 1979 SR5 long bed). I used […]

You may think I’m obsessed.

It’s true, I’m obsessed.

It’s been a really, really long time since I had fun wrenching on a vehicle. I think the last time I actually had fun working on my car, I mean really working on it, was my first Toyota truck (a 1979 SR5 long bed). I used to do all kinds of crap to it, because it was so easy to work on. More recently, the only car I’ve really spent any time on was my red Jeep wrangler; mostly minor bolt-ons or removals.

I’ve never worked on my own motorcycles significantly; never really a been a big customizer. But when I set out to replace my Trophy (a big beast of a bike, all covered in full-body plastic), I had a couple of criteria: light, nimble, and most of all, no fucking plastic. I wanted to be able to work on it, whatever bike I chose.

When I settled, after considerable thought and research, on a Bonneville, I couldn’t have picked a much more customization-friendly platform. All the bikes in the bonneville family (The original Bonnie, the Scrambler, and the Thruxton) share a uniform frame, engine, and geometry; so parts are almost completely interchangeable. Being the product of a long history of chopping, bobbing, and café-ing, there’s also a huge market out there for parks, kits and gear.

There are literally dozens of vendors making and selling parts, and hundreds of easy bolt-on options. For a beginner, one could spend thousands before getting up into the range of work that’s actually difficult, and for experienced wrenchers, there’s really no limit to what you can do to these things. Like the original 60s Triumphs, they’re made to be re-made.

To say I’m having fun with this is an understatement; I’m having an absolute fucking ball.

My list of things to do is just getting longer and longer, from changes to the air intake (air box removal kit and air injection removal), to the exhaust (black pipes, predator cans), to the rear wheel (fatter tire), to a new tank to replace that tiny teacup of a tank the Thruxton comes with. There are about a hundred other things I could do, ranging from power increases to paint; time and money are my limits.

But here’s my next customization.

One of the common objections to the Bonneville family is the ugly-ass tail light and signal cluster, which looks like something off of a ’50s scooter or the back of an Edsel. There are many after-market tail-light and turn signal options that are more in line with the bike’s sixties/seventies styling.

Alternately, particularly among Café Racer enthusiasts, one of the most common mods is what’s called a Fender Removal Kit, or FEK, which removes the rear fender entirely, replacing it with a plate under the seat (to protect wiring), and a minimal tail-light and license bracket.

Every major Triumph parts dealer offers an option for this, each approaching it a bit differently. I wound up with the kit from British Customs, mainly because I liked the ‘cats-eye’ tail light (though also because the wiring harness they provide is particularly user-friendly).

To go with this, I chose a pair of turn signals from Harrison Specialties, which I just happened to stumble on via a Buell forum. They satisfied my taste for aggressive, bullet-shaped turn signals and super-bright LEDs. I admit it, I’m a whore for LEDs, I’ve replaced all the turns, all the idiot lights, the gauge illumination, and would replace all the lights on my car too, if I had the time.

Below are some pictures; compare the look of the rear fender here, to the new version, here and here. The difference in terms of a clean, classic, retro appearance is worlds apart, and I couldn’t be happier with it.

Other smaller mods are a ignition relocation kit from Joker Machine (who make the coolest shit ever), moving the ignition from next to the headlight (a dumb-ass place for it; it’s ugly there, and it’s awkward to reach), and small fairing-mount front turn signals, and a billet choke knob, also from Joker.

Below is a slide show; let me know if you can’t get to the whole set.

(this seems to be broken at the moment, it’s not clear why, but I’ll fix it shortly)

(Click to go to full-size photos)

There are a whole lot of other parts I installed as part of this, though most of that’s only interesting if you own a Triumph you’re working on. Read on if you’re interested in the hard details

One of the big headaches of a mod like this is that it’s hard as hell to get a clear answer about some basic details of how.

For example, converting a motorcycle from regular filament flashers to LED flashers requires several different mods, but which mods depends.

What does it depend on? There’s the question.

Flashers are a simple wiring system; two lights in one circuit, (per side), all wired together, thourgh a simple mechanical relay.

The relay assumes a certain resistance in the wires; this is why turn signals will suddenly blink way too fast if one light goes out.

Adding LEDs has the same effect; LEDs have way less electrical resistance than old fashioned bulbs. So old-fashioned relays react as if the bulb’s burned out?

SO how do you slve that? There’s the issue.

One of the things that makes Unix daunting for new users to grasp is that every single question has multiple answers, and every problem has multiple solutions. This is because UNix, unlike windows or MAcOS, was built by engineers, for engiuneers. Engineers like options; they like choices. They like to know they can apply the solution that they like, and then hasho ober which is better and why.

SOme electrical systems seem to be devised the same way; everyone solves it a bit differently.

If you do a bit of research, you’ll find there are dozens of solutions to this LED signal problem; every vendor gives you different one. Some require load balancing devices that cost upwards of a hundred dollars; others will tell you all you need is a resistor, or two, or a diode kit, or some special wire doohickey.

Odds are most of these work; but they don’t all solve the exact same problem.

Luckily, this is pretty fucking easy for the Bonneville.

There are two issues to solve.

One is caused by the circuit having only one indicator on the dash (the ‘idiot light’) to tell you that your turn signals are on, with both sides wired though it. This works great for regular signals, but when you put on LEDs, you get feedback in the line, and every signal on your bike will flash in unison; not at all useful as a turn signal.

There are basically two ways to fix this; one is to wire a diode in line (like this kit from Küryakyn). That’s really cheap (seven or eight bucks, though shipping may double that), but requires some incredibly awkward wiring in areas of the bike that are hell to get yoru hands into particularly if you have big hands like mine. The other (the easy way), is to replace your flasher bulb with this incredibly simple Idiot Light kit from NewBonneville, which both gets you beautifully bright lights, but also fixed the diode problem.

The other issue is the ‘fast flash’. And this is the one where some vendors will sell you hundred dollar gadgets.

Luckily there’s a way easier, cheaper solution. The K&S 24-0005 relay. You can find this several places like Amazon or Biker Highway, but I picked it up from one of my favorite triumph-specific vendors, Bella Corse, for $19.99.

This is plug and play; once the Idiot Lights were fixed, this plug-in relay replacement had my four LED turn signals flashing correctly with no fuss whatsoever.

It’s really just that simple; once the idiot light kit was in place and the relay was plugged in, it all worked, for forty bucks (and that got me the idiot light upgrade as well).

The whole process was so easy, yet it was something I found incredibly intimidating. I even posted on the Triumph RAT forum about it and got no good info on it, which I’ll be correcting shortly by adding this info there.

Now that it’s all done, I’m really, really happy with the result; though of course, I already want to change some of the things I’ve already done, and do a dozen more.

10 thoughts on “Thruxton mods: FEK and flashers”

  1. Here’s the deal…..
    From time to time I check your site to see what’s new. We tend to have similar interests. When I checked today – voila! – I see you’ve bought a Thruxton. Absolutely beautiful! Love the modifications. The reason I’m commenting is because I’m buying a bike and settled on a Triumph. It started last summer when I started riding again after 20 or so years. My friend had an old 80’s 1100 (Sabre?) which he let me use. Loved riding – hated the bike. Way too tall for me (I am not a big guy) and I was perched on the back of that thing like a tick. But…the bug bit and I wanted a bike again. Flash forward to this year and I’m now window shopping. Yesterday I went to a Triumph/Harley dealership to look around. I was intending to look at the Triumph Speedmaster. Nice bike – not sure about the forward controls. I then walked past a Bonneville and did a double take. Looking online, the Bonneville didn’t interest me. In person I was impressed. Sitting on it, it fit me perfectly. The more I looked at it the more I liked it. A Thruxton was sitting next to it so I sat on that. Stunning bike (Black) but I’m concerned with the seating position. I felt crouched over with the weight on my wrists. ‘Course, this is in a showroom with my buddy holding it up. At home I googled Bonnevilles to see about modifications. Many owners ditch the bench seat for a style much like the Thruxton. I really like some of the add-ons out there for the Bonnies (which has a nice upright seating position). But…….the image of the Thruxton keeps popping up in my mind. I don’t want to get the Bonnie if I’m just trying to make it into a Thrtuxton but I also want a good riding position. I live in New England and intend to ride for short bursts only – mostly back roads. Lots of potholes around and I want decent ride quality (plus my back is 43 years old…). So…now comes the decision process.. I did test drive a Sportster 883 but still like the Triumph. The Sportster felt like I was always reaching forward. I’m also going to look at a Moto Guzzi Café v7 tomorrow. The Bonneville is in the top running as of right now.

    Any thoughts?

  2. Matt, you know, the thing with a Bonneville is they’re made to customize; the bars can be changed out, and there are dozens of different options available. Check out a few threads on Triumph RAT ( and you’ll find probably a hundred on bars.

    One note on the Thruxton – make sure you’re looking at the ’09 or 2010 model. The earlier ones has completely different bars; they had sport bike style clip-ons which are several inches lower. The new ones (The EFI (fuel injected) ones) also have bar-end mirrors like mine, so it should be pretty clear which you’re looking at.

    The thing is, though, that you can compromise from either starting point, making the thrux less cafe or the bonnie more cafe.

    I’d suggest you try to get a test ride on the Thruxton if you can.

    The other bike I think you’d LOVE is the scrambler. I was *this* close to pulling the trigger on one, and I still want one. It’s the same engine, same frame, basically the same bike, with slightly different suspension, different tuning (more low end torque), more aggressive tires, and an ‘off road’ appearance.

    The scrambler is absolutely the most pure FUN bike I’ve ever been on. I got one as a loaner when I took my bike in for service and I had a hard time giving it back. FOr pokin’ around rough roads, it’s EXACTLY teh bike you want. It’s no trail bike, even if it looks it, but it’s quite happy on a dirt road. It had a thumpy engine that’s just a joy and with an after-market exhaust (which all the bonnevilles need first thing), it sounds amazing.

    The Scrambler is a great starter bike for new riders, but it also appeals to veteran riders.

    Let me know what you wind up doing. There are a lot of good choices for classic bikes (there’s a ducati sport classic also in this niche), but it’s hard to go wrong with a Triumph; the price is friendly and they just go and go (the lack of used models all over shows how much people hang on to them, which also means good resale).

  3. Just received delivery of my ’10 Thruxton Special Edition.

    About the only mod I can do to that particular museum piece is to remove the AI in order to save the pipes.

    I am curious to hear about your AI removal project, when/if it happens.


  4. The AI removal went off without a hitch. You’ll need a 50 ohm, 10 watt resistor if you are looking to remove the solenoid, otherwise you’ll hear constant clicking from it.

  5. Thanks for the writeup on the LED issue! As a result I’ve ordered the exact same components. One question I do have is whether you had to do some splicing to connect the LED turn signals to the main factory harness (I’m thinking of connecting the rear signals at the shock mounts…and the front signals at the original location of the front signals).


  6. Hey Karl,

    So happy I stumbled upon your site before upgrading the LEDs. I did the exact same thing. However I have an issue with my turn signal idiot light not blinking when the turn signals are on. I have the amber color bullet signals from Harrison Specialties, a relay from Superbrightleds and the Newbonneville idiot light kit. The turn signals function as expected and the idiot lights work for everything except the turn signal light.

    Do you have any advice on this?

  7. My idiot light wires don’t appear to have enough current. I just bought an ’09 Thruxton and the previous owner did the LED signal conversion and relay or whatever to slow the flash rate. I cannot see the idiot light and am just back into biking and drive through a city and confuse many a car driver.
    I just now installed the New Bonneville idiot light conversion and found the turn signal light was already an LED, but much smaller that in the upgrade kit. I see no light coming from the LED on the bike or the New Bonneville one. If I put a bulb from another idiot light I can barely see it glow so I know I have current.
    Is there an easy answer or do I live with it or do a complete re-do?
    Love the bike!

Leave a Reply

Your email address will not be published.