| Author | Message | ||
     Jandj_davis |
I was browsing the updates to Motorcycle-USA.com this morning, and came across this really interesting article: http://www.motorcycle-usa.com/Article_Page.aspx?Ar ticleID=5476&Page=1 I checked out their website, and sent them an e-mail asking if they thought their heads would work on a Buell motor, or if they would consider expanding their market a bit. The dyno charts look pretty interesting at least. http://www.rpmhemi.com/ | ||
| Rick_a |
You could save several grand and pretty much do the same with a good port job. | ||
| Slaughter |
OK now... so they upped the compression ratio and don't take that into account when making claims about increased power? Might be just a minor point but it caught my eye. Wouldn't you really have to spin these motors a whole lot faster than they normally turn in order to NEED that much more flow than could be gained over a stage 3 head? Just asking... | ||
| Sarodude |
Honestly, I think there's more to multi valve heads than just the number of valves. One (or two?) of the things that comes to mind is combustion chamber shape and spark plug location. Also, I can't help but notice the distinct lack of 4 valve air cooled heads in general. I believe what you'll find on semi-recent implementations (with the exception of a Honda off-road single) is engines / parts not intended for extended run times. I don't recall the exact wording or the exact ANYTHING, but I seem to remember a Porsche engineer commenting about how very very difficult it is to properly and practically cool multi-valve air cooled heads. Also, as Slaughter suggests, an apples to apples comparison sure would be nice.... -Saro | ||
| Barker |
IIRC Trojan's race XB has 4 valve heads. | ||
| Jaimec |
The air/oil cooled BMW "R" bikes have used four valve heads since 1990. Even before that in the early eighties (when I first got into motorcycling) Suzuki was running four valve heads on their GS1000 and GS1100 air cooled IL4s as well. | ||
| Ridrx |
The 4 valves are more about port velocity than sheer flow numbers. Amount of air is irrelevant if it's sitting still. Really big valves and runners kill low end because the velocity of the incoming fuel charge is dramatically slowed. A 4 valve arrangement allows similar volume of air while maintaining a much higher port velocity, thus more completely filling the cylinder.= more power. Sometimes the 4 valve arrangement will allow for even larger flow numbers, a 2 valve arrangement is usually limited by the valves diameter. | ||
| Jaimec |
Four tiny valves can also be opened and closed a LOT faster than two BIG valves. Although two tiny valves can flow more air than one big valve, that's just one of the advantages of a four valve head. Smaller valves use smaller springs, and since they have less mass they can also be opened and closed much more quickly. Four small light valves also wear out the valve seats more slowly than two big valves slamming into the seats over and over too. | ||
| Ridrx |
+1 | ||
| Rick_a |
A long stroke slow reving twin doen't need four valve heads. There's plenty of American V-8's with two valve heads out there in all manner of applications including motorsports. | ||
| Djkaplan |
"Also, I can't help but notice the distinct lack of 4 valve air cooled heads in general." I can remember off the top of my head that at least three of the Japanese manufacturers (not sure about Kawasaki) have produced air-cooled 4 valve heads in engines ranging from inline-4s to singles. The current Yamaha Warrior has 4 valve heads (and air cooling), BMW boxers have them (they're oilheads I know, but not water cooled), and Moto Guzzi just released 4 valve heads for the air cooled Griso. | ||
| Djkaplan |
"There's plenty of American V-8's with two valve heads out there in all manner of applications including motorsports." The Dodge Viper and Chevrolet Corvette have 2 valve heads and pushrods. | ||
| Natexlh1000 |
Of course it can be done but it's not as easy when the rear head's exhaust port doesn't get any air. The more holes you punch in a casting, the harder it will be to keep it from warping. Anyone here have any experience with those Feuling heads from the mid 90's? | ||
| Ducxl |
Good one Nate  The heat factor.4 valve heads were debunked long ago in these long stroke engines.BMW does use them,but their engines are not as undersquare as ours.Still one pushrod opening two valves too,on a common rocker arm.Go to an oversquare twin and you can use 4 valves because the chamber is very wide.PT Barnum would have something to say about these heads.. Here are my newly ported and cammed 4 valve Ducati heads ready for use on an engine that CAN use them  | ||
| Ducxl |
Look ma! No valve springs in these! And they'll spin the engine to 12k RPM | ||
| Anonymous |
The XBRR has two valve heads. And it beat all the bikes with heads like DucX1 is showing in the French ProTwins this year, and won at Willow last week over them, and won at Daytona a week ago over them. We don't need four valves in these motors! But if you want a Buell with an engine using four valve heads, we make them too! | ||
| Ducxl |
But if you want a Buell with an engine using four valve heads, we make them too! Another good one!  The 1125r can USE 4 valve heads.But why? | ||
| Reepicheep |
My 9 motor revs 1000 RPM faster then the XB12 motor, with exactly the same valve train. | ||
| Aesquire |
With proper design, a 4 valve head can flow better at Low rpm's than a 2 valve head that flows the same ( as the 4 valve ) at High r's. I had a twin swirl combustion chamber GS1100E back in the day, and I'd say 4 valve is optimum, considering Yamaha has gone BACK to 4 valve from 5 this year. I'm not saying you can't get the same peak power with 2 valves, as 4, and if it does make a diff. in a undersquare engine I don't know, but you "should" from all I've read, get a "fatter" or broader spread of powerband with a 4 valve. Remember the Feuling? both 4 valve heads & "W" motors/choppers. Some local shop bought the heads, I keep meaning to get a pair of them. | ||
| Ducxl |
It's because of the shorter stroke Reep. | ||
| Anonymous |
Here are a couple of reasons, DucX1: because the 1125R is water cooled, because it is DOHC, and because with the stroke it has it can rev way higher. With 9000 rpm air cooled engines there's no advantage with four valves, in fact some disadvantages. So with 7500 rpm motores it's of even less use. We had development sets of these decades ago, and they did not add value. | ||
| Teeps |
Anonymous Posted on Thursday, October 25, 2007 - 07:10 pm: Here are a couple of reasons, DucX1: because the 1125R is water cooled, because it is DOHC, and because with the stroke it has it can rev way higher. With 9000 rpm air cooled engines there's no advantage with four valves, in fact some disadvantages. So with 7500 rpm motores it's of even less use. We had development sets of these decades ago, and they did not add value. The "value" would be bragging rights... my (insert) is bigger than your's. Those heads are definitely designed to do one thing for sure, and that is to sell. And from the photos on the web site they are hardly, what I would consider, hemorrhoid... er "Hemi" combustion chambers. | ||
| Glitch |
My what a big insert you have there. Is it hand made? | ||
| Diablobrian |
IIRC the 4 valve heads on our air cooled motors have trouble with burning the web between the exhaust valves too leading to failures. I talked with Erik about this at Homecoming 2006 and he said that they had built 4 and even 3 valve heads to test and that they found no real advantage and significant complication of the design/more parts that aren't needed which would add to cost. All that for no real gain... on a stock motor. On a heavily modified motor there might be some advantage, but that's not what we are talking about here. | ||
| Reepicheep |
Exactly Duc... So why are people "fixing" the valve train to be able to rev higher? Do they want a bigger unusable margin then they already have? I think a long stroke two valve engine is probably breathing great at low RPM's, which is why its emissions are so good, and low RPM power is so nice. | ||
| Glitch |
I'm a big fan of simple simplicity. | ||
| Paint_shaker |
K.I.S.S. And I ain't talking about the band either... | ||
| Bad_karma |
For those that have access to the data. Ported, large valve XB heads will flow better than 297 cfm on the intake side and 210 cfm on the exhaust side? Thanks for any data provided. Joe | ||
| M2nc |
I would like Hemi heads, be they two or four valve. I read somewhere that someone made a Hemi head with two valves for an XB.  That being said, as much as I like the 1125R, I would love to see more of the XBRR motor on the street. A 8000rpm Hemi head Aircooled Lump could produce 120hp from the factory would be a nice stable mate for the 1125R. | ||
| Glitch |
Two valve Hemi Heads for HD Buell? |
