fact or fiction?

[sportyone]

hi guys, :wave:
if you read the various advertising speel or hype about the difference between a Bonneville & a Thruxton particularly the carb'd versions, triumph maintain it's thruxton is the most high performance of the two. does anyone really know the actual facts. most part specs & manuals etc say the parts like cams etc are much the same, adverts say hotter tune, high compression different carb needles etc, if so to what specs are they different, jetting seems the same according to the workshop manuals out there. some info says it runs a higher compression, some say it is identical. has anyone out there really ever checked this out for sure ?
seems bloody strange & stupid why there is so much secrecy over the actual facts with the real specs between the two models.
it would really make it so much more easy to mod a Bonneville to similar specs if any of this was true or could be verified.

someone out there must really know, there is too much here-say and bull to really get the facts IMO :huh:

 

[dschief]

They are the same engines. In fact, Bonnevilles with the 790 engine have hotter cams than the Thruxton or 865 Bonnys.

 

[qwenzel]

You can go to www.Hermys.com they have all the Bonnie's + Thrux's, and their spec's listed by year. From 2001 thru 2009.

 

[sportyone]

They are the same engines. In fact, Bonnevilles with the 790 engine have hotter cams than the Thruxton or 865 Bonnys.

yes, I am aware of the older 790cc cam etc differences, however I am more interested in the 865 carb'd model differences.

I would appreciate anyones info,so long as it's really fact thanks :shh:

 

[sportyone]

You can go to www.Hermys.com they have all the Bonnie's + Thrux's, and their spec's listed by year. From 2001 thru 2009.

thanks Quentin,
it does show some specs on the two models however apart from the mention of hotter cams in the text about the Thruxton, the rest including the compressions are the same, but no mention of it anywhere in the specs. I suspect like I said it all sounds like a lot of bull or hype if you ask me, :shh:
not sure why really or what would justified the $ 2000 price difference apart from the slightly meaner cafe racer look, which we all know can be achieved easily far cheaper.:huh:

 

[dschief]

yes, I am aware of the older 790cc cam etc differences, however I am more interested in the 865 carb'd model differences.

I would appreciate anyones info,so long as it's really fact thanks :shh:

Sorting fact from fiction is related directly to sorting through marketing hype and actual part numbers of engine parts and specs.
The Thruxtons used to have about 500 more revs allowed by the ECM, than did the Bonnevilles, which may allow for a few more horsepower. Don't know about the newer 865 Bonnevilles though. Sorry if that does not answer your question, but that's all I have.

 

[Tabletop]

The thruxton was introduced in 2004. In 2004 it was the only one with the 865cc engine, with 69 HP. The 790's output in 2004 was 61 HP at crank.

In 2005 the T100 and Speedmaster got the 865cc engine. However, the T100 used different cams and needles in the carbs. The T100's factory numbers were 63 HP (Speedmaster 54 HP) and the Thruxton still at 69.

In 2006 some change was made to the cams in the T100, giving it 66 HP.

I remember in 2005 and 2006 alot of discussion on the other site about dropping Thruxton needles into the T100 to get increases in power.

From 2007 on, all of the carbed bonnie based bikes used the same engine/cams/needles, with the exception of the cams for bikes firing interval at 270 for the scram, america and speedmaster.

I imagine the EFI bikes are also mechanically identical. So...it was fact, for a few years, but in the past 5 or 6 years it is no longer.

 

[dschief]

It's funny that the repair manual lists the lift and duration as exactly the same for all 865 cams. Good point about the carb needles, I had forgotten about that.

 

[drlapo]

would the bend in the head pipe contribute to the difference? the bend in the Thruxton pipe occurs later than in the bonneville pipe

 

[mikenva]

yes the headers are better on the thrux.Dont bet money on the factory hp numbers though they dont show on the dyno that the 865 has more hp more torque yes but the bigger motor wont make the power up top the 790s do with the better cams.

 

[sportyone]

would the bend in the head pipe contribute to the difference? the bend in the Thruxton pipe occurs later than in the bonneville pipe

yes I believe the longer distance before the 1st bend is crucial to flow increase, with the Thruxton, which I notice has also been adapted to the later EFI models too ? from my understanding this longer length does give additional flow which may give quicker response equaling extra power, But I'm not sure if it is fact or hype too ???

don't know why Triumph have always pushed the concept that the Thrux was the hotter of the two 865cc 360deg carb'd models, when it isn't true.
be very nice if they really were, but to just sell them as a sleeker looking machines with a higher price doesn't gel when we all know that they are basically tuned & mechanically the same ! :shh:

 

[dschief]

Is it the location of the pipe bend, or is it the fact that it is a smoother bend (not as hard of a direction change) that benefits the flow of the Thruxton pipes?

 

[Kirkus51]

Odd that just as soon as you change pipes, which 99% of us do, it's a whole new ball game on all the 865s. Depending on flow restriction, you get better HP with just that one swap.

 

[strokerlmt]

I DO NOT speak from authority....just dumb trail and error. Stock 865 baffelectomy better feel, to stock headers + dominators, to 988/813cams FCR39s + stock headers no cross over dominators better and better to what I have now which is a 2 to 1....1.5 flanges to 1.75 headers to 2 inch throat collector welded to a (1) dominator muffler. The flow gets better and better and I am pleased with the results.
LMT

 

[begenius]

facts about Thruxton

In my opinion Thruxton is better in all aspects from similar year Bonnie std orT100
carbTHRUXTON vs carbT100=Diferent carb needles/higher revving limiter (8100rpm)/better exhausts-smoother bends+longer head pipe part =more hp from stock 865 motor.Maybe a litlle hp more but a 8-10% plus power for sure from factory(mostly in higher RPM)

with all other cafe racing parts (clip ons/alu rims/seat+cover/rearsets/better front brake/adjustable levers-front sus preload/white faced instruments/different suspension/sorter fenders)do the trickery about higher selling price

all in all carbThruxton it is a better and sportiest OEM Bonnie

It costs more so it must be more expensive to the pricelists

Eugene

 

[mikenva]

ahhh the rev limit on all 865 motors on the carb bikes was rases not just the thrux the 790 had a 7400 rpm limit the 865s have around 8000 rpm limit the new efi thurx are higher but not the carb bikes.
The main gain the thrux has is in the headers you can put aftermarket mufflers and thrux headers and pick up power over bonnie headers and after market mufflers .Many dyno runs have proved that the thrux headers are the best stock headers.D&D makes better headers on there race sytems then the trux headers but the bends are like the thrux headers.but the pipes are bigger.
But the highest hp carbed triumph twins so far is a bonnie and its a old 03 model.But then it cost more then 2 thrux lol.

 

[Aussie_T100]

The official Triumph parts book shows the Thruxton & Bonneville 865 carbed bikes have the same part numbers for the following parts:-

Cylinder head assy, inlet camshaft, exhaust camshaft, piston assy, conrod assy, crankshaft, balance shafts, airbox, carb assy, inlet manifolds & igniter.

The only difference between the bikes is the exhaust system.

The EFI Thruxton does however have a unique part number for its pistons which I believe are 9.8 to 1 compared to 9.2 to 1 for the rest of the twins range. The part number for these Hi comp pistons is T1121455. The EFI Thruxton also has a higher rev limit I believe but this has not been confirmed yet.

 

[PieMan]

The Thruxtons used to have about 500 more revs allowed by the ECM, than did the Bonnevilles, which may allow for a few more horsepower.

Fact: all carb'd 865's have an 8,000rpm limit, it doesn't change between models.

 

[dschief]

Fact: all carb'd 865's have an 8,000rpm limit, it doesn't change between models.

Fact: Thrux pipes on a Bonnie 790 lose 1.5-2bhp off the top end compared to standard Bonnie pipes.

Good to know that! I wasn't aware of the 865 Bonnevilles having the same rev limit as the Thruxtons, as my Bonneville is a 790.
Anyone know the reason for the Thruxton pipes killing top end power on a 790? That doesn't make any sense to me that a pipe, designed for an engine with more rev's, would be less efficient on an engine with smaller and lighter pistons and more cam duration (which in itself relates to an engine with more high rev bias), but a slightly lower rev limit.

 

[mikenva]

Fact: all carb'd 865's have an 8,000rpm limit, it doesn't change between models.

Fact: Thrux pipes on a Bonnie 790 lose 1.5-2bhp off the top end compared to standard Bonnie pipes.

thats not what alot of others have seen with thrux headers they picked up top end hp.So I would not say thats a fact lol.It maybe with the mufflers you ran.