 790 cams in an 865.
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Joined: Aug 2006
Posts: 35
Greenhorn
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OP
Greenhorn
Joined: Aug 2006
Posts: 35 |
Just finished installing a set of stock 790 cams in my 865 Speedmaster and have to say the results are quite impressive. No local dyno to check the numbers...Wanted to do a run before and after. The machine pulls hard all the way to the revlimit and seems to have a butt load of more pick up. They also seemed to eliminate a flat spot in the midrange. A worthy upgrade of the 865 powerplant.
Are you classified as human? Negative...I am a meat popcicle.
06 Speedmaster. 790 Cams, Supertrapp Exhaust, AI removed, 150 Mains, Thruxton needles, Airbox removed with K&N Pods 180 degrees.
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 4,518 Likes: 32
Loquacious
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Loquacious
Joined: Jan 2005
Posts: 4,518 Likes: 32 |
Interesting variation on the choice of upgrades.
Was it a straight swap or was there anything else involved?
Another question if I may ... any idea what the 790 cams cost?
Bedouin.
Blessed are those eyes that have seen more roads than any man! (Homer).
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Re: 790 cams in an 865.
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Joined: Aug 2006
Posts: 35
Greenhorn
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OP
Greenhorn
Joined: Aug 2006
Posts: 35 |
Straight swap...just pay attention to the timing marks.
New 790 cams are $300 each...I did not buy new ones however. If I had to purchase new cams I think I would have gone Thunderbike.
Are you classified as human? Negative...I am a meat popcicle.
06 Speedmaster. 790 Cams, Supertrapp Exhaust, AI removed, 150 Mains, Thruxton needles, Airbox removed with K&N Pods 180 degrees.
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Re: 790 cams in an 865.
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Joined: Sep 2007
Posts: 1,668
Learned Hand
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Learned Hand
Joined: Sep 2007
Posts: 1,668 |
Does Thunderbike make 790 cams?
Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 790 cams in an 865.
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Joined: Aug 2006
Posts: 35
Greenhorn
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OP
Greenhorn
Joined: Aug 2006
Posts: 35 |
Not that I know of....but they do make what looks like a vicious 865 cam....but word is that 790 cams are almost as hot in a 865. I know my bike was sure woken up.
Are you classified as human? Negative...I am a meat popcicle.
06 Speedmaster. 790 Cams, Supertrapp Exhaust, AI removed, 150 Mains, Thruxton needles, Airbox removed with K&N Pods 180 degrees.
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 4,518 Likes: 32
Loquacious
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Loquacious
Joined: Jan 2005
Posts: 4,518 Likes: 32 |
Quote:
....but word is that 790 cams are almost as hot in a 865. I know my bike was sure woken up.
And that's without cylinder head modificatios ... nice!
Bedouin.
Blessed are those eyes that have seen more roads than any man! (Homer).
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 828
3/4 Throttle
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3/4 Throttle
Joined: Jan 2005
Posts: 828 |
So what exactly is the physical difference in the cams(790, 865, Thunderbike 865)? The gearing has to be the same in order to keep the timing correct but there isn't much else you can 'adjust'. Is it the shape of the lobes, weight, or what? Inquiring minds want to know.
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Re: 790 cams in an 865.
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Joined: Sep 2007
Posts: 1,668
Learned Hand
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Learned Hand
Joined: Sep 2007
Posts: 1,668 |
Quote:
So what exactly is the physical difference in the cams(790, 865, Thunderbike 865)? The gearing has to be the same in order to keep the timing correct but there isn't much else you can 'adjust'. Is it the shape of the lobes, weight, or what? Inquiring minds want to know.
Yes, it's the shape of the lobes.
Howbeit when He, the Spirit of truth, is come; He will guide you in all truth:
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 6,821
Bar Shake
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Bar Shake
Joined: Jan 2005
Posts: 6,821 |
Quote:
Quote:
So what exactly is the physical difference in the cams(790, 865, Thunderbike 865)? The gearing has to be the same in order to keep the timing correct but there isn't much else you can 'adjust'. Is it the shape of the lobes, weight, or what? Inquiring minds want to know.
Yes, it's the shape of the lobes.
And the position.
Contra todo mal, mezcal; contra todo bien, también
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Re: 790 cams in an 865.
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Joined: Aug 2006
Posts: 35
Greenhorn
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OP
Greenhorn
Joined: Aug 2006
Posts: 35 |
Yes...it is subtle difference...at least to the eye...I put the cams side by side on my bench..and the difference didn't jump out at me...but upon closer examination there is a difference. And of course a big difference when installed...
Are you classified as human? Negative...I am a meat popcicle.
06 Speedmaster. 790 Cams, Supertrapp Exhaust, AI removed, 150 Mains, Thruxton needles, Airbox removed with K&N Pods 180 degrees.
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 7,643
Monkey Butt
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Monkey Butt
Joined: Jan 2005
Posts: 7,643 |
Swopping the cams in an EFI speedy to the carb america, should make a difference then you are all saying?
What are we talking and is it worth it, as I was thinking when it goes in for the shims to be done they can do that at the same time if the buggers are going to charge me £425.00/$900.00.
Ray(UK)
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Re: 790 cams in an 865.
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Joined: Feb 2007
Posts: 23,217 Likes: 61
Fe Butt
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Fe Butt
Joined: Feb 2007
Posts: 23,217 Likes: 61 |
I think we are talking the 865 carb cams to the 790 carb cams not to the 865 FI model.Not sure what the 865 FI cams look like or what effect putting the 790 cams in the FI 865.
I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!
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Re: 790 cams in an 865.
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Joined: Aug 2006
Posts: 35
Greenhorn
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OP
Greenhorn
Joined: Aug 2006
Posts: 35 |
Yes, Carb 865 cams to carb 790 cams.
Are you classified as human? Negative...I am a meat popcicle.
06 Speedmaster. 790 Cams, Supertrapp Exhaust, AI removed, 150 Mains, Thruxton needles, Airbox removed with K&N Pods 180 degrees.
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 8,639 Likes: 3
Old Hand
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Old Hand
Joined: Jan 2005
Posts: 8,639 Likes: 3 |
The swap is 790 cams into a carb 865. The 865 exhaust valve timing is very mild with the valves closing before TDC, while the 790 valves close way after BDC. The long duration allows the inertia of the exhaust gasses flowing down the pipe to pull out remaining exhaust and pull a bigger charge into the cylinder.
I don't have the timing specs for the FI engine, but judging from the power spec's, their cams are probably as good as the 790.
Something to consider is that the 865 exhaust cam is probably a lot better than the 790 on turbocharged engines.
Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 7,643
Monkey Butt
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Monkey Butt
Joined: Jan 2005
Posts: 7,643 |
Quote:
The swap is 790 cams into a carb 865. The 865 exhaust valve timing is very mild with the valves closing before TDC, while the 790 valves close way after BDC. The long duration allows the inertia of the exhaust gasses flowing down the pipe to pull out remaining exhaust and pull a bigger charge into the cylinder.
I don't have the timing specs for the FI engine, but judging from the power spec's, their cams are probably as good as the 790.
Something to consider is that the 865 exhaust cam is probably a lot better than the 790 on turbocharged engines.
Thanks Ed, probably not worth me doing the mod then, will probably sell them on eBay
Ray(UK)
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Re: 790 cams in an 865.
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Joined: Apr 2007
Posts: 3,063 Likes: 8
Loquacious
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Loquacious
Joined: Apr 2007
Posts: 3,063 Likes: 8 |
Anyone know if the EFI 865 uses the same cams as the carbed 865 or were the 790s installed. The horsepower and torque are somewhat higher on the EFI model. Is it because of the cams or EFI? Does anyone know?
12 Rocket Roadster
03 Bonneville America
69 BSA Firebird Scrambler
73 Yamaha TX 750
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Re: 790 cams in an 865.
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Joined: Jan 2005
Posts: 8,639 Likes: 3
Old Hand
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Old Hand
Joined: Jan 2005
Posts: 8,639 Likes: 3 |
The power rating for the FI 865 is about what I would expect if a 790 were bored to the same displacement. That makes me think the FI valve timing is much better than the carb version, though maybe not identical to the 790. Since the reason for the 865 carb valve timing was to get the same emission reduction effect as an EGR system, they very likely programmed the FI to run clean enough that this is no longer needed.
Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python
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Re: 790 cams in an 865.
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Joined: Mar 2008
Posts: 1,586 Likes: 1
Learned Hand
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Learned Hand
Joined: Mar 2008
Posts: 1,586 Likes: 1 |
Allright,better get back to work.
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