gearbox bearings

IBA...GATOR · Dec 29, 2014

Going thur my gearbox & changing out the bearings... I noticed that the outer main bearing has a metal shield a metal spacer & seal..... I have been told that I can use a unshielded bearing for this what do you all think ... interested in your knowledge.....

It's not how you ride thru the storm, but rather how you dance in the rain..... Tripower

texasSlick · Dec 29, 2014

tripower said:
Going thur my gearbox & changing out the bearings... I noticed that the outer main bearing has a metal shield a metal spacer & seal..... I have been told that I can use a unshielded bearing for this what do you all think ... interested in your knowledge.....

It's not how you ride thru the storm, but rather how you dance in the rain..... Tripower

I would prefer no shield and let the bearing bathe in oil, rather than depend on the internal lube of a sealed bearing.

Slick

Onder · Dec 29, 2014

Well most bearing wear comes from foreign material so maybe a sealed bearing is better.
A Norton non unit gearbox probably runs cooler than a unit bike so less worry about the lube
as a cooling medium.

texasSlick · Dec 29, 2014

Onder said:
Well most bearing wear comes from foreign material so maybe a sealed bearing is better.
A Norton non unit gearbox probably runs cooler than a unit bike so less worry about the lube
as a cooling medium.

Undeniably true! So what causes a sealed bearing to ultimately fail? IMO, it dies of its own wear products trapped in its lube, something an unsealed bearing also suffers if packed with grease (unless it is fitted with a zerk and flushed with new grease periodically). OTH, if an oil bath is present, wear particles are carried away, trapped by a sump magnet, and eliminated by periodic change of oil.

This is a situation requiring each to make his own call, after weighing the pros and cons.

Slick

Hobot · Dec 29, 2014

I was told to remove the inside seal only by vendors and ancient owners for above reasons and do for no problems in that area.

baz · Dec 29, 2014

maybe a little off subject but when a BSA B44 is raced it is recommended that the seals are left on both sides of of the timing side main bearing the argument being that the lube inside the bearing is enough for the bearings lifespan any additional oil will be contaminated to some degree and shortens the bearings life, this is what is done by Mark at PES performance CCM to improve the racing lifespan of the B44 bottom end when raced ,,,,,,,,,,,,,,,,,baz

Hobot · Dec 29, 2014

Well then that settles it for me, like so many other little Commando details it boils down to personal philosophy at the decision point to work fine either way.

IBA...GATOR · Dec 29, 2014

Thanks for the response... The bearing that I just took out is out of the 65 AJS G15 gearbox, The mainshaft bearing has a metal shield to the outward side a 3/16 shim that the & a lipped rubber seal... the inner is a open bearing.. my question is can I run a non shielded bearing seen how there is a shim that sets in front of the lipped seal... or would it throw out the gear oil... Tripower

Onder · Dec 29, 2014

If it is sealed on the outboard side then you reduce oil leakage out from the gearbox and the open inboard side will allow for gear lube to splash in there.

Ive not seen a test on sealed v unsealed but my guess would be that there is less pollution from the bearing wear than from material generated by
the gearbox which has a much greater ability to generate micro and not so micro particles of steel and bronze.

Im in the 2RS camp.

toppy · Dec 30, 2014

Onder said:
If it is sealed on the outboard side then you reduce oil leakage out from the gearbox and the open inboard side will allow for gear lube to splash in there.
.

According to the Mick Hemmings Dvd on gearbox rebuild this is how the original old style bearings were but modern bearings are not common with a single seal.

Onder · Dec 30, 2014

Very easy to pick out one of the rubber seals. Remember bearing were shielded not sealed back then too.

gearbox bearings

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