Revolution-X engine - Harley Davidson Street Forum - Street 500 and 750
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post #1 of 46 Old 02-25-2014, 03:09 PM Thread Starter
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Revolution-X engine

So far what do we know about this motor that makes it different from the existing evo series motors ?

The liquid cooling and 60deg V-twin are the obvious one but other difference have they made ? I could barely find any info on this engine and anyone who has any input please discuss it here .

Even the official mileage figures and dyno charts are lacking . Unless HD releases either(I dont expect dyno ) , it will be some time before we are familiar with the true characteristics of the motor. milleage can be calculated once delivery starts but getting access to a dyno is next to impossible in india . Only expect those numbers once european and american customers get their bikes .
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post #2 of 46 Old 02-25-2014, 05:43 PM
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hey @basuroy I found some information, noting too deep diving but its more than we had I believe.

Single Overhead Cam
4 valves per head

Rev X has a shorter stroke which should translate to a higher reving mill
Forged steel counterweighted crank

I'm fairly certain that the Street 750/500 Revolution X engines are derivatives of the VRODs Revolution mill...

Inside the Revolution | How It Works Magazine
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post #3 of 46 Old 02-25-2014, 05:56 PM
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The V-Rod engine is a 60 degree V-Twin with a single balance shaft between the cylinders driving the water pump on the right. It has double overhead cams, shim under bucket valve actuation and has both cam drives on the left side of the engine. The spark plugs are located in the center of the bore with coils built into the spark plug boots. The engine architecture is highly over square and red line rpm is 9000. Cast pistons ride inside wet steel liners rather than a plated bore or iron sleeved bore. On the V-Rod, induction is straight down through two throttle bodies with velocity stacks and a large air box located above the engine where a gas tank is traditionally located. The V-Rod carries it's fuel in a plastic tank under the seat.

From scrutinizing the photos of the Revolution X engine, the cylinder heads appear to be interchangeable front to rear. If you look at the castings, you see the front head has the spark plug on the left and the cam drive on the right, while the rear head locates the spark plug on the right and cam drive on the left. The head are identical but rotated 180 degrees from each other. This orientation allows an intake towards the center of the V and the exhaust ports at the extremities. It also makes the bike less expensive to manufacture.

Harley claims the bike has four valves per cylinder operated by a single overhead cam on each head operating the valves through rocker arms and lock nut adjusters, not the DOHC shim under bucket design of the V-Rod. Red line rpm is 8000 compared to 9000 for the V-Rod. No word that I have found on bore and stroke dimensions or what kind of cylinder bore is used. No word on counterbalancers either and you can see cooling hoses exiting the engine on the left and diving down somwhere between the cases and the countershaft pulley, very different from the V-Rod engine. It is hard to tell the configuration of the intake tract, whether it has a single throttle body feeding a plenum between the cylinders or dual throttle bodies like a V-Rod. You just cannot tell from the photos with the gas tank in place. What is apparent is that unlike the V-Rod, the Street uses separate coils you can see under a cover on the left side of the engine where the V-Rod hangs it's whimpy horn.

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post #4 of 46 Old 02-25-2014, 06:23 PM Thread Starter
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Interesting info from both of you guys , very acute observation from you @Desert Tortoise. The entire post was a mine of detailed information .

I'm not familiar with the technical aspects of the engine though I have a fair idea what most things mean . Overhead cam means no pushrods right ? I have seen the evo engine has external pipes(if that is what we call them) for the pushrods which I assume moves the rocker arm to actuate valves. This I understand is old technology ?

Overall the changes that one can notice - are they better technology wise or primarily done for cost cutting ? Do these changes make it a better enginered motor than evolution (on paper ) ?

Single cam as opposed to separate cam for intake and exhaust affects the performance or reliability adversely ?

Do these changes mean lesser vibration ?

Expected fuel economy of the 750 should be better than the 883cc motor but by how much , the 883cc evo gives a return of 17kmpl within city , what is the approx figure(+20 ? ) you expect in comparision to that from the revo-x ?


BTW a few queries regarding other HD bikes-
1. What is the redline for the 883c sportster motor ? In your opinion , the revo-x is the better engineered motor ?
2. V-rod I understand is hated by HD traditional fans. But objectively viewed , is the motor well engineered and reliable or not ?

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post #5 of 46 Old 02-25-2014, 06:56 PM
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I have two V-Rods and perform all of my own maintenance, including adjusting valve clearnaces, so I have a high degree of familiarity with the V-Rod. I have that hand memory of the engine you only develop from working on them enough times (not that it isn't reliable, it is, but I put a lot of miles on the bike and that drives maintenance actions).

If you think about a valve train, the valve spring has to control everything in the valve train, the valve, pushrod if any, rocker arm and lifter. Like any piece of metal, all of those parts have a resonant frequency, sometimes many frequencies and the only thing preventing resonant vibrations is the valve spring. The more mass that valve spring has to control, the less able it is to control all that mass, which means the more mass you have the slower you have to spin the engine to allow that valve spring to keep up, otherwise you get valve float (valve spring compresses and cannot close the valve fast enough). That is when pistons hit valves and bad things happen to your engine.

In general, overhead cams mean fewer parts and less mass for the valve spring to control. If you operate all the valves with one cam through rocker arms, the weight and flexibility of the rocker arm will limit how fast you can spin the engine before you risk breaking things, but with rocker arms you can use lock nut adjusters to set valve clearances, and this can be done without much work or disassembly. If you operate the valves with a cam located directly over the valve stem through a bucket, you minimize the mass the valve spring has to control and thus can use more rpm. With buckes you have to have means to adjust valve clearances, and most engine manufacturers use sized shims placed either under the bucket on top of the valve stem, or in a pocket on top of the bucket. With the shim under the bucket there is no way the cam lobe can scrape the shim off the bucket and do damage at high rpm, so most really high rpm engines use direct acting cams with shims placed under the buckets. The drawback to putting the shims under the buckets is that you have to remove the cams to replace shims, and you have to make excruciatingly careful measurements of the valve clearances before you pull the cams, and then measure the shims carefully so you can calculate what size shim you need to get the correct clearance. I have this down to a 7-8 hour drill on the V-Rod now, which is darn good. But my BMW K100s use shim over bucket, and I can check clearances in maybe 45 minutes, even if I have to swap a couple of shims along the way.

Remember horsepower = (Torque X RPM)/5252. As long as torque does not fall off, raising rpm gives higher horsepower and a faster bike. The limit is how fast you can fill the cylinder and how fast the flame can travel across the bore during combustion. The larger the bore, the more time it takes the flame to travel across the bore, so there are practical limits to how fast you can spin a big bore engine before you run up against the physical limits of combustion. No worries, just add more cylinders with smaller bores. That is why GP bikes are multi-cylinder screamers.

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post #6 of 46 Old 02-25-2014, 07:00 PM
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Oh yeah, the red line of a well built Sportster engine is around 7500 rpm. There are two things limiting this. Number one of course are those long pushrods. With beehive valve springs you can maybe push one to 8000 rpm before the valves float, but you will have to use very aggressive cams (meaning your engine won't last long) to get the engine to breathe way up there.

But the other big drawback of that engine is the crankshaft. Instead of a forged crank running on plain bearings with conrods side by side on a common crank pin, Sportsters and Twin Cams used a forked conrod (like an old radial airplane engine) running on roller bearings. The crank pin is pressed into the flywheels, and the whole thing spins on tapered roller bearings pressed into the engine cases. By 7500 rpm that mess is flexing so badly you are either skidding the rollers in the bearings or flexing the crank pin so badly you are spalling off chunks of steel. This is pre-WWII technology, a complete kludge on any modern motorcycle engine, but the bandanaheads won't buy anything else.

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post #7 of 46 Old 02-26-2014, 02:51 AM
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Thanks a Ton Basu_roy and Desert_tortoise for so detailed information, Its a very good learning for me
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post #8 of 46 Old 02-26-2014, 04:19 AM
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Quote:
Originally Posted by Desert Tortoise View Post
The V-Rod engine is a 60 degree V-Twin with a single balance shaft between the cylinders driving the water pump on the right. It has double overhead cams, shim under bucket valve actuation and has both cam drives on the left side of the engine. The spark plugs are located in the center of the bore with coils built into the spark plug boots. The engine architecture is highly over square and red line rpm is 9000. Cast pistons ride inside wet steel liners rather than a plated bore or iron sleeved bore. On the V-Rod, induction is straight down through two throttle bodies with velocity stacks and a large air box located above the engine where a gas tank is traditionally located. The V-Rod carries it's fuel in a plastic tank under the seat.

From scrutinizing the photos of the Revolution X engine, the cylinder heads appear to be interchangeable front to rear. If you look at the castings, you see the front head has the spark plug on the left and the cam drive on the right, while the rear head locates the spark plug on the right and cam drive on the left. The head are identical but rotated 180 degrees from each other. This orientation allows an intake towards the center of the V and the exhaust ports at the extremities. It also makes the bike less expensive to manufacture.

Harley claims the bike has four valves per cylinder operated by a single overhead cam on each head operating the valves through rocker arms and lock nut adjusters, not the DOHC shim under bucket design of the V-Rod. Red line rpm is 8000 compared to 9000 for the V-Rod. No word that I have found on bore and stroke dimensions or what kind of cylinder bore is used. No word on counterbalancers either and you can see cooling hoses exiting the engine on the left and diving down somwhere between the cases and the countershaft pulley, very different from the V-Rod engine. It is hard to tell the configuration of the intake tract, whether it has a single throttle body feeding a plenum between the cylinders or dual throttle bodies like a V-Rod. You just cannot tell from the photos with the gas tank in place. What is apparent is that unlike the V-Rod, the Street uses separate coils you can see under a cover on the left side of the engine where the V-Rod hangs it's whimpy horn.
Wow ,and here I was thinking medicine is the tough nut to crack @[email protected]
Thanks for all the explanation ,can u plz put it in lay man terminology and just tell us these new engines are better are they all show & no go ???
Being a novice it was difficult to understand anything ,well if I keep going through expert threads like these I think will learn a lot kudos to all you pro bikers in this forum ...
And thanx a ton for sharing

Regards:
Santosh kumar
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post #9 of 46 Old 02-26-2014, 11:13 PM
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This is straight from a Cycle World article: Separate aluminum cylinders are fitted with pressed-in iron liners, and the only difference between the 500 and 750 versions, which share a 66.0mm stroke, is the bore. The 500’s is 69.0mm, which makes for an actual displacement of 494cc. The 750’s bore, at 85.0mm, makes for a displacement of 749cc. Redline for both engines is 8,000 rpm, and peak power for the 750, though not officially announced, was said by one Harley rep to be 54 hp at 7,500 rpm, with 44 pound-feet of peak torque arriving at an unspecified rpm. A single balance shaft keeps the V-twin from shaking too much, and a six-speed transmission works with Harley’s familiar belt final drive. 2014 Harley-Davidson Street 500 & Street 750- EICMA 2013
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post #10 of 46 Old 02-27-2014, 05:26 AM
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Originally Posted by Sherri View Post
This is straight from a Cycle World article: Separate aluminum cylinders are fitted with pressed-in iron liners, and the only difference between the 500 and 750 versions, which share a 66.0mm stroke, is the bore. The 500s is 69.0mm, which makes for an actual displacement of 494cc. The 750s bore, at 85.0mm, makes for a displacement of 749cc. Redline for both engines is 8,000 rpm, and peak power for the 750, though not officially announced, was said by one Harley rep to be 54 hp at 7,500 rpm, with 44 pound-feet of peak torque arriving at an unspecified rpm. A single balance shaft keeps the V-twin from shaking too much, and a six-speed transmission works with Harleys familiar belt final drive. 2014 Harley-Davidson Street 500 & Street 750- EICMA 2013
This is awesome and really like the details.

Thanks for sharing

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