What's the deal with EVO cam bearings ?
 

Sorry no rumor,Evo's & some late Shovels had the problem.It is best to take care of it before you have a problem because if you wait and it goes the cases have to get split to get all the metal out (bigger bucks)! On the good side though with 97,000 on the bike if the bearing was bad it probably would have went many miles ago.They werent all bad !

I wish I knew more about it. I was kinda wondering the specifics myself. I recently bought an EV27 for no other reason than these guys here sold me on the cam bearing becoming an issue for me. I'm right at 20K so I should be fine till winter when I'm gonna take it apart, but I as well would like to hear more about it just for knowledge sakes.

Fair enough, so i will tell you.

The issue is centered around the inner cam bearing, and the 2 different brands of bearings that are used. One being the INA, and the other torrington.
The INA is a partial complement bearing, with a plastic cage holding the needle rollers in place(in relation to each other.
The torrington is a full complement bearing, meaning there is no cage, just a full house of needle rollers.
In the later seventies, HD tried the INA bearing in the inner cam bearing location, and it didn't work out very well, and they went back to the torrington(which had been used up until then).
Then, a little later, HD again decided the INA was worth a look, and tried it again. By then, the evo was the go, so it (kinda) became known as an evo issue. But it was a shovel issue first, and is, in reality, a cam bearing issue. Twinkies use INA stock, and that can be a problem as well.
There are known cases of stock cams failing with the bearing, but it is much more likely to happen with increased valve spring pressure, which, of course, is always the case with a higher lift cam.
So if you are changing cams, of course you would fit a new torrington.
But as you can see, many have done high mileage without a single issue, some even with aftermarket cams.
Even when there has been no "failure", I have no doubt that when the INA is removed, that the bottom area of the bearing, that takes the most load, will be BLACK,and very scary looking.
Hope this brief overview was at least a little interesting.

It is quite likely the majority of bikes out there are happily running up big mileages, like your bike, with no problems from that bearing, whichever one it has. If you have bought the bike secondhand, then at some time it may already have been done. My advice is do nothing! Your bike has got this far through life and only if you upgrade the cam or need other work done on the motor should you have it looked at.

The internet is a great place for learning stuff, but it can also make some things seem bigger than they really are. I know this bearing is a problem from reading websites like this one, but having owned Harleys since the 70s I have not come across anyone who has had that bearing fail. Some will do it, but not all of them!

The issue with the OEM bearing (INA) is that it has less rollers than the replacement (Torrington) bearing (along with other design issues). They are marginal for the OEM cams, and are a failure waiting to happen with any aftermarket cam, where increased lift/overlap/duration place stress on the rollers. SOP for any cam swap, is to replace the INA with a Torrington.

There are a couple pics floating around on this forum that show the physical differences.

It's an interesting thing, this cam bearing problem. The INA has the rollers in a 'cage' that stops them rubbing against each other (like any wheel bearing, ball or taper roller), while in the Torrington the rollers are 'crowded' and scuff against each other (like a steering neck bearing). In an engineering sense the INA should be superior, but experience in Evos contradicts that! Doesn't quite add up.

This is the result of an INA failure at 50K miles. This was a good outcome as the parts of the bearing didn't go through the engine before it was caught. (Stock cam)
Attachment 538912

Well, I for one am glad I now know more about this issue than just internet squabble. I really did buy that EV27 for the sole reason I was fearful the cam bearing was a disaster simply waiting to happen. And I figured, if that nosecone is coming off and I'm gonna have the cam in my hand anyways, why the heck put the stock emissions cam back in it. And the EV27 seems to be a favorite. See, it never hurts to ask.

That cam is a good choice. It was the first internal upgrade I did to my Glide. But then I knew nothing at the time about the bearing discussion!