has anyone here had a stock inner cam bearing fail (twin cam)..with all the talk about replacing the stock bearings with torrington bearings at cam change time I am wondering if there is any real justification for it...personally I have never heard of or spoken to anyone that had the stock type bearing fail, BUT I have heard a bunch of people say just replace them "in case" since you are in there...but I have also spoken with people who say the stock inner bearings are reliable and don't mess with them, and that the stock bearing are actually better because there is more room in there for the oil to circulate to keep them lubed, cool etc.....So, does anyone here have any opinion based on experience that might help to clear this up for me????

 

this was rife on the early twin cams, Donny Peterson wrote some great articles about the causes and results of bearing & cam drive failure.

There were a number fo revisions to the cam drive, pinion bearing end play specs and other fixes... this is part of why i stayed with my evo until the TC was 10 years deep.( So, no I have not personally had a cam bearing fail)

although the failed bearing shrapnel was "officially" confined to the cam chest, steel, brass, copper and plastic particles could easily pass thru the pinion bearing into the motor case, and may migrate there long before the cam drive system failed.
The motion of the pistons causes varying positive and negative pressure in the cases, which can blow/suck crap right through the bearings

inner cam bearing swap was standard on the evos as well when changing to a performance cam which puts more stress on the bearing.

the concept of a PM fix 'while in there" is that the cost of labor is already covered, so why not

any performance work performed on a motor soon becomes a search for the "next weakest link". parts are designed and engineered for the expected forces, if upgrades increase these forces, then failure will happen, whether in the motor, the primary drive, clutch or ...

Mike

 

I don't know the real answer, one supported by data and not speculation, either. So that's a good question. Maybe Dawg or some of the other guys with a lot of shop experience might chime-in.

Just looking at the Torrington versus the stock, you notice more needles, so logic would seem to indicate less friction and wear per needle, so longer life. I don't think that the idea that the stockers have more lubrication opportunity is, at least visually, valid either. The needles are separated and held in place by supporting lands, so I don't know where that "extra" lub would reside.
Looking forward to some of the other input on this since, as you say, it is widely recommended during a cam change.

 

Why the MoCo does not go to the Higher grade bearings is a mystery to me....
I had my cams changed when first purchased, factory bearings still there.

 

Had the inner cam bearing go bad on my 2005 Ultra @ 24,000 miles; spewed needle bearings all throughout the engine. See pic

 

The 07 and up have a 1" bearing, that is an upgrade from the 7/8" that caused some problems. If you have the 1" I wouldn't worry about it. Andrews Cams, the leader in cam manufacturing technology, does not believe there is an issue. Who will you believe, internet hysteria or Andrews? And if you don't believe me send Andrews a e-mail and ask them, that is where I got my info.

 

I don't believe in internet hysteria exclusively ...that is why I am asking the question...also I have a post 07 bike...and I am in the same feeling as Andrews...but, I am always interested in more first hand experience...it seems to me that there is a fair amount of folks that believe more is always better...in this case I think that more is the same....

 

On an '07 and up, I wouldn't open the chest just to change them, but if your doing cams why not spend $18 to replace them? Hardly seems hysterical to me. If I didnt have access to the tools needed, I might not replace them, but even spending $100 on the tools I wouldn't consider "hysterical".

 

I agree and haven't heard of any stock bearings that have failed, except one that was reportedly installed backwards at the factory. My dealer does replace inner bearings for all cam jobs, but use the stock INA's in the HD cam-install kit, claiming they've had no failures even in high-output applications. I'm referring to the 1" INA's in newer bikes, and I don't know what their policy is for earlier TC engines. Evos always got Torringtons, as they had even smaller (3/4") inner bearings (only one) that weren't nearly as robust as those in later models.

As to why the Moco doesn't go with a "higher-grade bearing," I think it is because there is no need. They also changed from Torrington/Timkin to INA crank bearings midway through the early-TC era, and I think they did this because they were cheaper and could handle the stress of stock and light-to-moderately modified engines. How many of those have we heard about failing?

All that said, I decided to use Torringtons for my cam job, simply because they are cheap (<$15/pair) and it isn't that big of an issue to replace them once the cam plate is out, although I did have to buy a tool to extract and install them (Beatty). I do think it is a toss-up, though, and that the 1" INA's should work fine.

 

True! But that bieng said if you are changing cams you would be an idiot not to change the bearings be it Inya or Timkin. Swapped my cams at 90,000 on my 07 and the stock bearings had little wear. better Bearings are cheep insurance. I wonder too if there are a lot of inner bearing failers on post 07 models.