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What if someone placed a 2017 Thruxton engine in a 2017 Bonneville T120

17K views 71 replies 27 participants last post by  Dougl1000 
#1 ·
With the similarities in the engines of the 2017 Bonneville T120 and the 2017 Thruxton I wondered whether the High Power engine of the Thruxton could be mounted in the Bonneville T120 frame.
I wondered how difficult it would be and what changes in performance would there be as a result.

The additional 17 HP is a 21.25% increase, and the additional 5.2 FT-lbs of torque is a 6.7% increase.

Bonneville T120
Compression 10.0:1
Max Power EC 80 Hp (59kW) @ 6550 rpm
Max Torque EC 77.4 FT-lbs (105 Nm) @ 3100 rpm

Thruxton 1200 R
Compression 11.0:1
Max Power EC 97 Hp (72 kW) @ 6750 rpm
Max Torque EC 82.6 FT-lbs (112 Nm) @ 4950 rpm

I would venture a guess that the increase in acceleration would be hardly noticeable.

I once owned a 2002 WRX that I had some engine work done to increase the HP at the wheels from 150HP to 200HP (33.3% increase). It was a noticeable increase in performance.

Consider this a thought experiment.
 
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#4 ·
You would essentially get on a T120 the increase in torque towards the higher RPM, and with it the increasing rate of power output, more sportive for sure,

But then still with the T120's tall gearing, steel spoked wheels, comfy shock absorbers and moderate rake and trail.

Now I understand your question is maybe a matter of keeping the gorgeous style of the T120 while adding some pep's, but it would take many changes to make it really work, and in the end you would probably have a Thruxton on your hands.

Better try and put a Bonnie's tank and seat on a Thruxton, in my opinion.

My 2cc

NN
 
#6 ·
I have a new thruxton and rented a new t120 for a week.
I found the. T120 lacking in throttle response and overall power delivery.
The thruxton has a much livelier engine with no noticeable lack of torque.
Perhaps the gearing difference explains some of this.
Overall, in my opinion, the thruxton has a much better engine
 
#9 ·
Well, these bikes are not meant to be ridden the same way. You would'nt push a T120 in the revs as you would a Thruxton. Of course, if you like the exhilaration of peak torque at high rpm, you won't like the T120.

Now low-rpm, city or cruising, 2-up, with luggage and a classy, relaxed stance, the T120 is my girl.

And i prefer its stunning good looks too --the reason I surmise our OP posted.

NN
 
#8 ·
It's the same engine with a different head, cams and higher compression. I don't see why the head wouldn't be interchangeable. Maybe Carpenter or Neville Lush can come up with domed pistons and cams for the T120. That would do the trick. You'd have to find a way to tune it. Dynojet doesn't make a PC for the Bonnie and I'd bet hacking the ECU would kill it. Why would anyone do this for 14 hp? The Capenter kit for the Rocket adds over 100 hp.
 
#19 ·
I was told head is skimmed, cams are same, so just skim & flow the head that is what I am going to my bobber to give it some more pep
I have PCV on my R & my bobber, PCV is also available for the T120. I already have handlebars on my R, perhaps I should take the T120 tank off my bobber & see how it sits on the R.
 
#11 ·
As a matter of aesthetics I do prefer the looks of the T120 over the Thruxton. I also prefer the rider's position/posture on the T120.

I am not seriously consider trying what I posited above. It seemed an enjoyable "what if" thought experiment.

I expected that your responses would reveal aspects of such a conversion that I had failed to consider.

Triumph Bonneville T120

Triumph Thruxton

As NN65 suggested "Better try and put a Bonnie's tank and seat on a Thruxton, in my opinion."
Plus handle bars to allow a more upright seating position, would be the easiest approach to getting a "Thruxville" or a "Bonneton".
 
#69 ·
For easier comparison, re-posting this here to see the power graphs.
 
#13 ·
"Better" begs to clarify: for what? You saw the torque curves Farwalker posted; what you feel in the seat of your pants (yes, your butts, for the less elaborately courteous) is the torque.

Sport bikes will try and keep torque high at the highest possible RPM, to maximize power, often at the cost of low-end torque. Hence the feeling of the bike pulling and pulling on and the need to push the revs high.

The Thruxton, actually, doesn't even give up on low-end torque. That's a cool engine.

A city/road/2-up/groceries/touring/all-rounder T120 will rather offer much torque low in the revs, where you have more relaxed and precise control over it.

Not the same bike, not the same purpose.

You sure cannot ask the T120 to do the same as a Thruxton when it comes to exhilaration and clearing tight corners at speed. But I would say you might find it harder to have a Thruxton do the all-around biking that we ask of our T120 Bonnie's day-in, day-out.

NN
 
#14 ·
Imagining a similar concept for my 2016 green Thruxton S. I'll be asking my dealer in Spokane to install the Spiegler handlebar conversion kit to my machine at its first service. Will also be investigating relocating the pegs to approximate the position of the T120 or Street Twin. Triumph's UK site indicates that the T120 may be available in a (competition) green and white scheme next year. Hoping this tank and a T120 comfort seat would fit on the Thruxton chassis without too much fuss (the seat lock location looks different). Benefit of the T120 tank would be its reduced length. Think this combination would yield a motorcycle that has most of the best characteristics of its donors.
 
#25 ·
Looking at the performance curves above, I see the Truxton has more torque than the T120 at all rpm's. I no longer see the purpose of the T120 engine. The lower compression means it can use regular instead of premium gas, that's it, I don't see any other advantages.
 
#26 ·
It could be marketing strategy (wink, wink). For years, Triumph restricted the power on the Rocket by closing the secondary throttle plates with their stock tunes. When software came out for users to open up the plates, everyone did and got back the power. Then in 2010, Triumph announced the "unleashed" Rocket, where all they did was open the secondaries with their stock tunes. In the coming year, expect a high performance T120 and 1200 cc America and Speedmaster.
 
#32 ·
Yes, I see, I stand corrected. I looked in the owner's manual and, sure enough, all Bonneville models call for 87 octane, whether 11:1 or 10:1 compression ratio. I don't understand that, but there it is.
 
#50 ·
This thread is funny.....talking about modern Bonneville's and HP. There are about a thousand bikes out there with more HP and a lot of them for less money. If you bought your Bonny for performance, then you are a dingbat. I love the Thrux and if my reconstructed shoulder could take it for more then 60 minutes I would most likely own one. Alas my shoulder has issues, so I have a T120. I have owned everything from a HD Electra Glide Standard to a Ducati 1098 and a KLR + about 20 other rides including the Triumph S3 which will smoke either the Thrux or T120. That said this lineup of new Bonneville's is awesome. I have always loved the looks of the Bonny's but the lack of realistic power kept me away until I rode the 1200 powered T120. I didn't ride the Thrux because I knew that would be a problem......lol. Anyway the way I see it, we have an assortment of choices now with the modern classics and to compare them is asinine really because each was made for a different purpose, a different buyer/rider. Enjoy what you have or buy another....................Triumph made one for everybody!
 
#51 ·
Yep. A Thruxton 1200 is definitely a lifestyle choice, not a logical performance choice. It's great for a mid-career rider like me (50)- I still like a bike that goes, but I don't need the latest escape velocity capable weapon. I also happen to have a soft spot for the classic look I recall from the older bikes of my youth (not ones that I rode, but ones that were already old when I started- my first bike was a Ninja 250).

Who knows? Maybe when I'm 70, I'll spurn the electric hover bikes of the time and buy a classic reproduction imitating today's Speed Triples...look, it has fake wheels to cover the hover units! [emoji23]


Sent from my iPhone using Tapatalk
 
#52 ·
Agree..I'm 65 and back riding after a 4.5 year layoff due to orthopaedic issues in my right shoulder/neck. I used to have a 2004 Thruxton that I changed for a Tiger, because I couldn't take the riding position anymore. In the end even that was too much.

Now back on a Thruxton R, it is all the bike I ever wanted and both a joy to behold as well as a flexible, fluid, responsive ride. But although my neck and back are not complaining my left hip is. An hour is about the limit before I need to get off and walk about. So, if/when Triumph produces a Bonneville R with the engine and suspension of the Thruxton R I'll be VERY interested. Anything to keep me on 2 wheels.

Reading this thread it is interesting to compare the torque delivery of the Thruxton and Bonneville motors. Yes, it makes more power, so HP is justified, but it also makes more torque and delivers it over a wider rev range, from the dyne graphs posted:

Thruxton: more than 70 ft lbs from 2500 to 6500 rpm.
Bonneville more than 70 ft lbs from 2500 to 3250 rpm.

From my perspective the Thruxton motor is better, a flat torque delivery over a wide rpm range.
What is not to like?
 
#62 ·
... I wondered whether the High Power engine of the Thruxton could be mounted in the Bonneville T120 frame <snip>
I lay myself to sleep many nights wishing to put a big 955 triple ('02-05) engine in my (fantasy) second Thruxton... I truly love everything about the Thruxton, but the ballsy howl of those triples cannot be surpassed.
 
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