Sealed main bearings?

[JC]

Gents,

I noticed in Doc's post on the 125KTM that it has a sealed main brg on the RHS of crank - which of course may not be OEM

Has anybody had experiencs running sealed bearings for main brgs?

[Hoony]

the seals cannot be on the crank side in the cases as they will not be lubed at all and will seize.
most bikes have non sealed bearings and have crankcase oil seals outside of the cankcase to seal from G/box oil / air

[JC]

Yes I know that hoony.

But sealed brgs are rated at hi rpm for continuous running & of course have their own lubrication. Whether its sufficient or not is another matter.

I've never been game to run them on the crank, but wondered if anybody else has, esp when I read Docs post finding one on the KTM125 crank.

[GMC]

I believe they would be sealed for industrial applications, I don't see it as logical to leave these seals in place in a motorcycle engine, even in the gearbox. It would stop the oil flowing through, I always dig these seals out before I put in an engine.

[JC]

Thanks GMC,

Thats my hunch too. Also the extra heat of a 2T engine. Just wonder if anybody has tried

[facthunt]

I have found sealed bearings in a couple of parts motors on gear shafts. The seals were noticably blistered
and the bearings well worn. Seems they get a little warm. Wouldn't recommend it.

[LWC82PE]

the bearing on the main shaft behind the clutch drum on the YZ 490 i pulled apart had the outside seal left on it but the inner seal facing inside the gearbox removed. not sure if it should be like that, my thought is to remove both seals to allow maximum oil lubrication from both the clutch side and gearbox side which is what i would normally do.

[matcho mick]

have run sealed bearings in all my race motor gearboxes for years,especially output shaft bearings,(where not pressure fed),basically keeps the box contaminants out,probably not a big deal in 2smoke seperate boxes,but in combined engine/box applications no probs!,actually think from memory yamaha did so in some late DT175's in the 80's,ducati certainly did!,facthunt you gotta think how hot was the rest of the box to blister the bearing seals  ,ran my outer bearing on matcho racemotor sealed both sides,(runs two driveside mains,1 sealed ball for crank location,1 major loadbearing open roller),just my opinion,certainly works for me,

[Doc]

Thanks for that Mick, I was starting to get a little worried but the sealed main bearing in the KTM donk is genuine OEM and as per parts book. While near all the pre'85 KTM125's were hand grenades this bearing was not responsible for said failures

[pancho]

reading matho micks comments reminds me of eh holden gearbox problems the rear race was wearing out at about 15000miles which led to after market double race bearings being fitted which lasted longer. then GM started fitting a fully sealed bearing in place,all the mechanics i knew said what bullshit that will never help.    guess what no more premaure wear!.it is an established fact that a certain amount of fine metal particles are always present in gearbox oil ,while it doesn't effect gears mutch its murder on bearings.  cheers wally.