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I would imagine to streamline production and enhance parts interchangeability.
Plus the consumers want bigger engines.
 

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Bad for the company self esteem when the little brother 790s hand the big brothers their hat under all circumstances. :-D
 

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:-D :-D :-D

Larry
 

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Ouch Rodburner. My girlfriend was with me when I bought Bonnie Red. She said bigger was better so I got the T100.
 

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The Bonneville range is Triumphs "entry level" bike. While increases in displacement and torque are nice, the 790 gave folks returning to motorcycles (like me) plenty to keep them interested without being overpowering. A friendly, fun ride. It makes sense to utilize 865 motors across the line but now you are talking about a bike that is only 135cc's away from a 1000. That can be more money for insurance even though the power is not really that much different. I think Triumph should go the other way with the Bonnie, perhaps a 650 or 750 with 55/60 hp and torque so that folks can get into bikes at less operating cost.
 

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I think that it has to do with emissions regulations.

The anemic cams found in the 865 engines, with their significant reduction in overlap in comparison to the 790 cams, should make for a "cleaner" engine. (...They tell us that the 865 is "tuned for torque", but don't believe Them...tuned for torque like a 1976 Pontiac maybe, see link below for my point...) If they used these more "earth friendly" cams without the displacement hike, the resulting power output would be unacceptable. For that matter, it's border line unacceptable even WITH the displacement boost.

If Triumph were to use catalytic convertors and fuel injection, they'd probably be able to use higher compression ratios and more performance oriented valve timing while still meeting emissions requirements. Just take a look at BMW, Ducati, and Buell and what they have been able to do with their respective air-cooled twins with these bits of modern technology. The downside of this would be increased cost to a bike that is already not exactly the bargain of the century.
1976 Pontiac
 

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you should be able to retard your exhaust cam one tooth on the 865 and get close to 790 cam specs and overlap. I havevn't tried it though, but it should work as long as no valves collide with pistons, but I think the room is there.
 

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The performance gains with the 790 cams are due to the increased duration; you can't get the same result with the 865 cams no matter what you do. :(
 

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Get a set of pre 2004 790 360 degree engine cams- they drop right in, have the same lift but longer duration. Lose some midrange for increased top end performance. :-D
 

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If that is the case then the thing to do would be to get the cam's you mention and then advance the exhaust cam one tooth. You end up with a inbetween range regarding overlap and get the best of both worlds.


Personally I'm glad I got the 790...( even though I added a bb kit )...cheaper insurance rate for the bike and a worthwhile displacement gain with the bb kit...and nicer cam's to boot.
 

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so what's an 865 rider to do? get some aftermarket $1000 cams?
I don't know. I got a 790.
but the after market cam makers are being pretty closed mouthed about the specs.
 

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On 2006-11-20 16:46, SCCTrim wrote:
If that is the case then the thing to do would be to get the cam's you mention and then advance the exhaust cam one tooth. You end up with a inbetween range regarding overlap and get the best of both worlds.


Personally I'm glad I got the 790...( even though I added a bb kit )...cheaper insurance rate for the bike and a worthwhile displacement gain with the bb kit...and nicer cam's to boot.
Trim with you having an '06 790 Bonnie Black, I think you have lucked out with the cams.
As per Jojje and Needcage dyno tests in the Cafe Ace and NTBF, it seems '05 and '06 790's have the 865 cams.

Sorry I did not notice this fact sooner, but even with an advanced 865 exhaust cam you are increasing bottom and midrange torque heaps, without losing any hp, this would make it a torquey mofo!!

I purchased '03 790 T-100 cams with 1500 miles on them from Bill Gately

I am runnning 865 intake cam and an advanced '03 790 exhaust cam which by my dyno simulation program indicates that this is the best combo for torque and hp, this combo is very simiiar to the stock 865 cams but slightly more efficient in Volumetric efficiency(VE)

I think it is possible to get 85-90rwhp out of a 865 with increased compression to 11:1 comp ratio and mild head work with 39 FCR or 42 HSR carbs

Cheers...............Agro

[ This message was edited by: agro on 2006-11-21 02:27 ]
 

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Agro, I guess you're still against the Thunderbike cams?

They seem to do different things than your cam combo, by moving the power up the curve...

a source of mine tells me he's sold several sets but has no feedback on them. I wonder how to interpret that.

[ This message was edited by: sweatmachine on 2006-11-21 08:49 ]
 

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I'm confused.

It seems that 865 riders want the 790 cams for better performance, but now agro says that the '05 and '06 Bonnie owners have "lucked out" because their 790s have the 865 cams.

I thought that I had "lucked out" because my 2005 790 has 790 cams, but maybe not.

What don't I understand here? Is the grass always greener on the other side of the hill?
 
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