This might make me look like an idiot but due to high prices I've mostly ignored the twin cam bikes as they were out of reach, so now with prices coming down i realize how little I know about this engine. anyways i kind of associated twin cam Harleys with dohc cars, never really paid attention to wheather there was one or 2 cams in each head..
However I realized while looking at a picture of a twin cam bike, hey dummy y does a bike with overhead cams have pushrod tubes duh.. then i realized the bike has 2 cams somewhere down in the engine kinda like an evo has one. so i wanna know whats the deal how does this work does one cam work one cylinder or does one cam work the intake side on both cylinders and the other work the exhaust? and how does this make the engine more powerful? thanks!!!

 

http://www.animatedpiston.com/TwinCam.htm

The little arrow on the bottom right reveals more of the engine each time you click.

This also might help: http://en.wikipedia.org/wiki/Harley-...win_Cam_engine

 

That is a pretty cool animation.

The only real difference is cylinder timing. You can change the cam timing on one cylinder at a time. Not really sure the value in it though. A single cam can be ground with the same timing offset, but this way is easier to find the right offset.

From where I sit, the two cams are a detriment more than advantage. It adds more chain driven timing and more components that need to be lubricated or that can fail from the lack thereof.

I could be wrong. Just my observations.

 

Actual not a whole lot of difference in Harley's engine going way back. Evo one cam TC two. Might also add that there is a TC and a TCb. The b motor has basically same set up as pictured in Keithhu's shortcut but deeper in the engine on the same side is a chain drive that drive two balance rotors cams that counter balance the engine to smooth it up. They have nothing to do with the cams that operate the push rods that move the rocker arms that open the valves. This probably ads some expense to a Softail. Not sure why Harley does not offer it on the big bike's at least as an option. Guess it just not old school. Also there is two cam shafts with two lobes each. One is gear driven as you see in picture or a chain and directly behind a plate is another chain running to the other cam shaft. The picture you see is not stock and has been converted to gear drive. Not sure when people do this if the gear setup drives the other cam or it retains the chain.
Most 4 cylinders in cars have similar setup. Both my 4x4 Tacoma and my Honda CRV have balance cam.

 

The stated reason for going to two cams actually makes sense when you look at the engine as a whole.

Looking at the design and my own research leads me to understand that the older single cam engines cam lobes and timing is actually a lot harder to design for and make work properly than it is in the Twin Cam engines.

The reason is the push rod angularity with the rockers. A twin cam has the cams centered under the rockers while the exhaust pushrods and rockers (the far front and rear on each cylinder) on the single cam EVO's have a much greater angle to overcome.

There is also the matter of the longer rods adding to the reciprocating weight and making it that much harder for the valve springs to prevent valve float.

At normal operating rpm range under 5000 rpm its not really much of a problem, but crank things up and that pushrod angle starts to make a difference as well as making it progressively harder for the valve springs to work properly.

If your making an all out drag bike you will have a budget that allows for substituting high tech materials to lighten things up and mega springs.

But on a high number production street bike where cost and reliability are the primary objectives. It's smarter and cheaper to redesign the engine than it is to start using a lot of high tech, hard to make and very expensive titanium parts.

In my opinion, and remember opinions are like ********,everyone has one and they all stink, they may have overdone things a bit when they made the "B" model because they introduced all new high rpm "problem's" with it. But they didn't bother to ask my opinion when they did it.

So I guess I'll just have to live with the smoother engine.

 

thanks guys, those links are really cool, and the info is great a I understand how it works now, although in a way it seems like there's just more parts that could break. but i can see how it might help in some ways. have a happy Christmas!!!