Why a single cam?

[actonern]

When the twin cam was introduced, the explanation I recall for the change over the EVO was that the two separate cams allowed a more linear force vector between push rods and lifters, reducing side load on the lifter bores.

With the new single cams now pushing 2 valve springs per cam lobe instead of one, won't that bring back the same issues EVO had?

[glens]

Geometry may have reverted somewhat, but depending on the mass of the valves (do the two new intake valves weight more or less together than the single old one) it may not be as much of a backward step as it would seem.  And maybe it's more backwards...  There are likely other benefits with a single cam that are more important to this generation of engineers, who just may all have been in elementary school when the last decision was made.

[HV]

Honda has a small 4 Stroke with a single Cam...single Lobe !

[choseneasy]

I thought the 2 cam design with silent chains was used to remove noise from the motor. Less motor noise meant the exhaust note could be louder.....
 

[autoworker]

$$$$$$ (At least in part.)

[rbabos]

Look at the bright side. Valve timing will be better between the two cyls.
Ron

[Ohio HD]

Look at the bright side. Valve timing will be better between the two cyls.
Ron

       I would bet the real reason, and stay consistent over time.

[CowboyTutt]

They made a big deal about reducing the number of moving parts to reduce parasitic drag too.  With better modern metallurgy maybe the side loads on the lifter bores not such a big issue anymore???  -Tutt 

[BUBBIE]

Hardened-Replaceable Lifter Blocks would have been Nice addition... Think?

Some reason the lifter block looks different but Why? EWhat am I not seeing? 

signed....BUBBIE

[Lakerat]

They made a big deal about reducing the number of moving parts to reduce parasitic drag too.  With better modern metallurgy maybe the side loads on the lifter bores not such a big issue anymore???  -Tutt

I never knew the EVO's had an issue with side loads on the lifter bores.

[tankshift]

Hardened-Replaceable Lifter Blocks would have been Nice addition... Think?

Some reason the lifter block looks different but Why? EWhat am I not seeing? 

signed....BUBBIE

What blasphemy! You are questioning the ALMIGHTY WISDOM of the MOCO? You will burn in HD HELL.

[BUBBIE]

 



Take a Listen to the ORIGINAL.... Arthur Brown, FIRE 1968.... Fits this New 8 ball...

http://www.Bing.com/videos/search?q=God+of+Hellfire+Song&view=detail&mid=C996807F244696CEDD53C996807F244696CEDD53&FORM=VIRE

signed....BUBBIE

[ScottFree]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

[Ohio HD]

Is that the same reasoning they went back to a rear belt drive in the 80's?     For style and heritage....     


https://www.youtube.com/watch?v=3406C6HaXl4

[JamesButler]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

BINGO!  Winer Winner, chicken dinner!

"C'mon people.  This is Harley-Davidson we're talking about".   Truer words were never written...LOL...  Let's not overthink it.

Let's not also forget that the MoCo had a great run with the Evo motor.  However didn't the exclusive control of that technology lapse thereby letting in the aftermarket competition?  So, the MoCo scrambled and came up with the Twin-cam solution.  Along with that "new" technology came all the bullsh8t marketing terms which promote the latest as greatest. 

It's all about the bottom  $$$ line.  Most Harley owners know very little and care even less about technology, present company on this "Tech" forum excluded, of course.  Look into the eyes of the average Harley demographic and start spouting terms like "metallurgy", "side loads" and "linear force vector push" and you'll see them glaze over and begin to shut. 

Going back to the late 80's the MoCo marketing department learned quickly that if it dangles a nice shiny chrome part in front of those eyes and spouts terms like "nostalgia" and "independence" and "freedom", and then ties those terms in with the "new technology", it could sell a polished chromed turd to its demographics.

So when the MoCo bean counters discover a potentially catastrophic trending loss to the competition, it tells the engineering department to switch it up - not necessarily to "improve or innovate" - but simply change it up and let the marketing department control the herd...

[rbabos]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

BINGO!  Winer Winner, chicken dinner!

"C'mon people.  This is Harley-Davidson we're talking about".   Truer words were never written...LOL

Let's not also forget that the MoCo had a great thing going with he Evo motor.  However didn't the exclusive control of that technology lapse thereby letting in the aftermarket competition?  So, the MoCo scrambled and came up with the Twin-cam solution.  Along with that "new" technology came all the bullsh8t marketing terms which promote the latest as greatest. 

It's all about the bottom  $$$ line.  Most Harley owners know very little and care even less about technology, present company on this "Tech" forum excluded, of course.  Look into the eyes of the average Harley demographic and start spouting terms like "metallurgy", "side loads" and "linear force vector push" and you'll see them glaze over and begin to shut. 

Going back to the late 80's the MoCo marketing department learned quickly that if it dangles a nice shiny chrome part in front of those eyes and spouts terms like "nostalgia" and "independence" and "freedom", and then ties those terms in with the "new technology", it could sell a polished chromed turd to its demographics.

So when the MoCo bean counters discover a potentially catastrophic trending loss to the competition, it tells the engineering department to switch it up - not necessarily to "improve or innovate" - but simply change it up and let the marketing department control the herd...

Would these be the same people that dropped the ball on the v rod? Let's price it out of reach for most and offer next to no accessories. Sure, that will sell.
Ron

[JamesButler]

C'mon, people, this is Harley-Davidson we're talking about. The single cam is there for reasons of style, and anything anybody says about mechanical reasons for it is just rationalization.

Line up all the Harley Big Twins, from Knuckle to M8, and it's clear the TC is the odd one. All the others make a powerful visual statement with the four chromed pushrod tubes converging on the timer cover. It's distinctive, it's "muscular" looking, and it's uniquely Harley. You might even call it "iconic." (You might also be able to protect it with trademark or design patent registration, as nobody else has this look.) Back in the late '90s, when the TC was designed, this wasn't as important because Harley had the nostalgic-cruiser market to itself. The TC was more about performance and emissions than maintaining the classic look.

That was then. These days, Harley is facing competition from Polaris/Indian, which has launched a frontal assault on Harley's dominance of the nostalgia market. The Thunderstroke engine was specifically designed to look like the flathead motors of Indian's heyday. That's why it has that otherwise goofy three-cam system (allows the pushrod covers to be parallel to the cylinder, as in a flathead), and the heads hang out to swallow the top third of the pushrods, and of course the rocker covers have bas-relief fins cast into them. And it seems to be working--Indian's still not selling anywhere near as many bikes as Harley, but their sales are growing, Harley's are more or less flat, and there are a lot of used Harleys for sale at Indian dealerships.

So now Harley plays that game. The M8 delivers four valves, two sparks, a counterbalancer, etc., etc., in an engine that looks "older" than the Twin Cam. Notice how many people are comparing the M8's lumpy rocker covers to the Knucklehead? I doubt this is an accident.

There may be good technical reasons why two cams are better than one. But style and "heritage" are more important to selling bikes. And the engineers will figure out how to make it work.

BINGO!  Winer Winner, chicken dinner!

"C'mon people.  This is Harley-Davidson we're talking about".   Truer words were never written...LOL...  Let's not overthink it.

Let's not also forget that the MoCo had a great run with the Evo motor.  However didn't the exclusive control of that technology lapse thereby letting in the aftermarket competition?  So, the MoCo scrambled and came up with the Twin-cam solution.  Along with that "new" technology came all the bullsh8t marketing terms which promote the latest as greatest. 

It's all about the bottom  $$$ line.  Most Harley owners know very little and care even less about their engine's technology, present company on this "Tech" forum excluded, of course.  Look into the eyes of the average Harley demographic and start spouting terms like "metallurgy", "side loads" and "linear force vector push" and you'll see them glaze over and begin to shut. 

Going back to the late 80's the MoCo marketing department learned quickly that if it dangles a nice shiny chrome part in front of those eyes and spouts terms like "nostalgia" and "independence" and "freedom", and then ties those terms in with the "new technology", it could sell a polished chromed turd to its demographics.

So when the MoCo bean counters discover a potentially catastrophic trending loss to the competition, it tells the engineering department to switch it up - not necessarily to "improve or innovate" - but simply change it up and let the marketing department control the herd...

[Jaycee1964]

Just tossin it out there but with 2 valves for each action one would think less lift is necessary depending on valve size?  I have no idea the size of the intakes on the new motor but say they are 1.5" x2 would be basically a 3" valve area.  my 124" has a 2" valve.  Wouldn't they flow more air IMO at a lower valve lift?  With a lower lift less valve spring pressure would be necessary to close the valve?  A single cam opening 2 valves with decreased spring pressure at once would not have as much pressure on the lobes?  Wonder if they are running "c" lifters..   


Just tossin' it out there. 

[PoorUB]

At low lift the circumference of the valve means more than the diameter, (of course they they go hand in hand) two 1.5 inch valves equal 9.42" circumference, where a 2" valve equals a 6.28". So two slightly smaller valves will flow more air.

[Ohio HD]

I'm definitely not a cylinder head expert, but I think the biggest improvement when going to four valves is a higher velocity port(s), air speed is up, combustion should be better too over the twin valve style.

[CowboyTutt]

Valve lip circumference is the name of the game, just don't tell a HD consumer as there eyes will gloss over according to some reports!  LOL 

Why Yamaha invented the 5 valve head, until they needed more compression and the 5 valve head and cut-outs got in the way of that. 

So much for my 85 Yamaha 700 Maxim X with 5 valve heads.  It was a hoot for a while.  Came on like a 2 stroke on top from 7-10K rpm. 

Regards,

-Tutt

[Durwood]

Valve lip circumference is the name of the game, just don't tell a HD consumer as there eyes will gloss over according to some reports!  LOL 

Why Yamaha invented the 5 valve head, until they needed more compression and the 5 valve head and cut-outs got in the way of that. 

So much for my 85 Yamaha 700 Maxim X with 5 valve heads.  It was a hoot for a while.  Came on like a 2 stroke on top from 7-10K rpm. 

Regards,

-Tutt

Andy, that's cool. I bought a 1985 left over "Super Red" Maxim in 1987....That bike was fast!!! 10k, no problem.

Sorry for the thread drift, just took me a trip down memory lane..... Back to the regularly scheduled programming.

[mp]

To get back to the original question, yes, the pushrod angles on the Evolution engine were not perfect but it was no problem for about 99.9999999% of them.  And certainly the "solution" of the chain-driven  twin cams turned out to be a cure that was worse than the "disease", considering all the very well-known problems with them.  Can you say "needless complexity"?  Even today I can't understand keeping the chain drive on the M8, as the gear-driven cam in my Evo has never made a sound that I ever noticed.  I assume S&S is already "gearing" up to make millions on gear drives for Milwaukee 8's.

[Herko]

"...can't understand keeping the chain drive on the M8..."

Off the top, crank pinion run out requirements are widened with chain driven cams.
Chains work well, and looks like the MoCo upped their game a bit with tensioner design.

[PoorUB]

I can't understand keeping the chain drive on the M8,

Chains are cheep, leaves more room for manufacturing tolerances. Less money to stamp out a sprocket than machine gears, plus hole locations in the engine block don't need to be spot on.