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Discussion Starter · #1 ·
Want to see if I have this straight.

Twin Cams inner cam bearings are needle bearing stock. When upgrading to gear drive they stay needle. Outer bearings are roller, but are replaced with ball.

I am told you do not not need roller because withouot the chain less force. What is the advantage of ball? Also why needle in the inner bearings? I was told needle not good for high RPM. Is this true? There used in sleds which are pretty high RPM, if memory serves me right.

I tried looking up in machinist handbook today, but just read that all three are considered anti friction bearins, such that low friction at start up.

Looking for a little schooling. I am electrical, not real good with bearings.
 

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your lucky you have bearings,I heard the new cam plates dont even use balls or rollers...the cams run right in the plate.
cams only run at 1/2 crank rpm.....3100ish at the most
 

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Discussion Starter · #4 ·
What is the advantage of ball over roller? Lighter? Smoother?
 

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Highly Seasoned Rider!
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berserker said:
Want to see if I have this straight.

Twin Cams inner cam bearings are needle bearing stock. When upgrading to gear drive they stay needle. Outer bearings are roller, but are replaced with ball.

I am told you do not not need roller because withouot the chain less force. What is the advantage of ball? Also why needle in the inner bearings? I was told needle not good for high RPM. Is this true? There used in sleds which are pretty high RPM, if memory serves me right.

I tried looking up in machinist handbook today, but just read that all three are considered anti friction bearins, such that low friction at start up.

Looking for a little schooling. I am electrical, not real good with bearings.
The OEM inners are made by INA....relatively few and short rollers in an inner steel cage inside of the outer shell. They are OK for stock but not the best.

The Torringtons which are generally used for an update/replacement are without inner cages, have full-length needles and the entire outer shell is full of needles which contact virtually the full length of the cam bearing surface.

TC's originally had ball bearings on the outer portion of the front and rear camshafts. They had lots of failures of the outer rear due to the bearing getting hammered by the chain and sprocket. Apparently the ball bearings on the rear cam wouldn't take the axial loads provided by the chain drive. The HD update was to use a sturdy roller on the rear cam outer bearing while retaining the original ball bearing on the front outer. This appears to work well with chain drives as the bearing can take some axial movement.

When changing to gear drives, however, S&S went to a ball bearing again since it appears to work better with the gears. Apparently there is less axial (sideways) load with a spur gear drive.

That's my story and I'm stickin' to it. :brows:
 

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Discussion Starter · #6 ·
What do Evos have for outer bearing? Ball?
 

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For the real anal ABEC 3 premium ball bearings can be had for a price to replace the HD outers for gear drive. They offer tighter ball clearance and improved QC.
 

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Knower of Stuff
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EVO, Plain Brass Bushing on outside of cam.
 
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