main bearing question

hombre · Post by **hombre** » 16 Feb 2007 08:55

Hi all,

I was wondering if anyone knew why the 500/501 has the 'split' bearing on the lefthand side. I have been told that you can grind 1 mm off the crankshaft and use a standard size one. Will this apart from being good to my bankaccount also be a good idea for the crankshaft or is the split bearing used for a very good reason?

EVguru · Post by **EVguru** » 17 Mar 2007 10:46

Interesting question. The standard (deep grove) ball race doesn't seem to cause any problems, even on tuned engines, but Morini didn't usually do things without reason (particularly if it cost money).

The split bearing is a 'four point contact bearing' and is designed more for axial loads than radial. That said, because of the very large balls (which you can now get in due to the split inner ring) the radial capacity is actually higher than the original ball race. The axial clearance may well be tighter than the original ball race and perhaps this was done to quieten the engine down, which is something they had issues with in later years.

The split Morini crank bearing is a 'special' and SKF can't provide a specification for it. However, there is a 4PCB that's exactly the same dimensions as the deep grove bearing. If you're going to modify your crank, then this may be a good choice.

Do you need to replace the bearing? If the oil is kept clean, then it should outlast most of the rest of the engine.

hombre · Post by **hombre** » 19 Mar 2007 19:50

Hi Paul,
Thanks for your reply. According to my SKF-dealer the one I have will still work as it should, so I want to use this one again.
I can't imagine Morini did it for noise restrictions, or else they would have done the same on the 350-engines, or did they do so on later 350 engines as well (NewYork, Coguaro)?
Anyway, I'll be recycling the old one which looks and feels good, because a new one is so expensive and grinding the crankshaft seems somewhat blunt. I am not going to do Paris-Dakar anyway