Main bearings

[brian kirby]

Why do the Sachs and KTM engines have three piece main bearings? Why should you not use a one piece bearing? Is there thrust loading of the bearing in these applications?

Brian

'73 Berkshire

[chicagojerry]

brian,it makes it easier to split the cases since the inner race and the bearing cage stay on the crank. i recently pulled apart a 250 ktm motor that someone had put normal bearings in so it can be done but i had to use a case splitter tool to get them apart.   jerry

[SouthRider]

It's mainly because the Germans/Austrians were almost possessed in their obsession to build things with the absolute tightest tolerances possible. FYI - this is why they lost WWII. American tanks could be fixed with spit & baling wire in the field.

Caged main bearings work just fine, however you cannot shim them.

Sachs motors are like fine jeweled watches. They can (and must) be set up to exacting standards to run properly, and then they run forever......

[brian kirby]

Thanks guys. I had no intention of putting one piece bearings in either of these type engines, I was just curious why the three piece bearing was used. It sounds like the KTM could fairly easily use them but the Sachs needs the three piece because of the shimming required to get it all adjusted?

Brian

'73 Berkshire

[Lew Mayer]

My Jackpiner had one-piece bearings in it when I took it apart.

Lew Mayer

[Rocket]

The 3 piece bearing makes splitting and putting back together very easy, hard part is shimming from scratch to get proper clearance.  You have to shim the 3 piece bearing to get the axial clearance correct.  A one piece bearing, the axial clearance is already in the bearing.  The new KTM's still use a bearing where one half stays on the crank and the outer race stays in the case, but you don't have to shim anymore.  East motors to work on.
Rocket