I was over at the J&P Cycles web site, checking on a sprocket and saw an important article regarding the twin cam bikes. Primarily, about the cam chain tensioners failing way to soon and trashing the engine. Mostly, not covered under warranty, according to the owners comments!:huh
Just so you can be all caught up, there is also a whole lot of inner cam bearings that go bad. This usually destroys the engine. (not re-buildable). Loose rollers inside the case is a bad thing, for sure. A gear drive cam set up eliminates the chain tensioner thing but it must be difficult to fit up correctly because a lot of those have a loud whine which may be from the fit of the gears, I'm not sure. There is a much better bearing available for the inner end of the cams too. A good practice is to pop off the timing cover and have a real close look at around 25000 miles.
06 on the Dyna's 07 on all the twin cams. If you warmed the bike up, never got on it hard until completely warmed up and did not lug the engine (the engineers want you to cruise at 2900 to 3100 rpm's) then the old tensioners would last 80k plus miles. The ones that ran into problems were the throttle blippers and those that thought they should be cruising down the highway at 2200 RPM's. They were having issues at around 25k miles.
When a manufacturer's biggest efforts go into "nostalgia", there's no surprise in that. What could have been, and never got a fair chance.
It has been common knowledge that the Twin Cam motors were not reliable since they came out. The cam drive is the main issue, but the "B" version of this engine has another problem, the balancer chains. I'll say it again CHAINS DO NOT BELONG INSIDE ENGINES The gear drive helps a lot, but the engines are so much more complicated than the EVO there are many more things to go wrong. The whine is due to straight cut gears. I have a Chevy S-10 with a 350 small block with a gear driven cam. I had a choice between helical gears (quieter) or straight cut gears (noisy but stronger) I like the noise. Sounds like a blower whine. Except for the 1981 Sturgis, all stock Harleys have had primary chains. But they seldom fail. And they are easily replaceable. If you see a Harley with a belt driven primary, it is aftermarket. BTW, what happened to all the EVO Harleys? Back in the early to mid '90s people were waiting a year on them and paying double price. Now I hardly ever see one. I look at every one I see, and sure enough there is that oval air cleaner. Hundreds of thousands of Harleys seem to have virtually disappeared over night. Considering the EVO was made from '83-'99, how could that many have just vanished from the face of the earth?