Layshaft bearing choice

Oakland850 · Apr 22, 2014

Hello all-! I am currently re-building my 74 Commando gearbox due to the typical failed layshaft bearing. The bearing kit I got contained a "superblend" roller bearing as a replacement. I know that roller bearing can handle higher loads than ball bearings in general, but they are also not very tolerate of slight shaft miss-alingment from case tolerence or shaft flex I believe. I just ordered the quality replacement ball bearing from Mick Hemmings and i am leaning towards using that one. He said he never had one fail, good enough for me. Anyone have any insight on this bearing choice? Thanks in advance for help! :?:

Torontonian · Apr 22, 2014

I can attest that all 3 of my gearboxes received the roller replacement and have helped 2 other riders perform the operation required. Probably nothing wrong with the Hemmings ball one as it would be of higher quality metals than when Norton was purchasing the cheaper alternatives to protect the bottom line. Think of the load forces and where they would occur , straight through that small bearing so it's roller for me ,never any issue arose. Your choice and a wise move to replace.

concours · Apr 22, 2014

Oakland850 said:
Hello all-! I am currently re-building my 74 Commando gearbox due to the typical failed layshaft bearing. The bearing kit I got contained a "superblend" roller bearing as a replacement. I know that roller bearing can handle higher loads than ball bearings in general, but they are also not very tolerate of slight shaft miss-alingment from case tolerence or shaft flex I believe. I just ordered the quality replacement ball bearing from Mick Hemmings and i am leaning towards using that one. He said he never had one fail, good enough for me. Anyone have any insight on this bearing choice? Thanks in advance for help! :?:

If the case alignment (or shaft flex) is enough to bother a roller bearing, the caged ball bearing is in trouble too. The shimming apears daunting to some, what's your experience level? Cylinder index? :lol:
Aside from the sure-to-follow pages of: "this guru says this, this zen master says that" stuff, it's just gears/bearings 101.
No matter which bearing you choose, treat the gearbox gently. I went with the roller based on facts presented on this forum.

johnm · Apr 22, 2014

[quote="concoursAside from the sure-to-follow pages of: "this guru says this, this zen master says that" stuff,
.[/quote]

I smiled at that.

Actually while philosophically Im in the "Dont tell me the answer -show me the reason camp"

Some days I just take the dumb and easy path and go with the guy with the grey hair and track record

concours · Apr 22, 2014

johnm said:
[quote="concoursAside from the sure-to-follow pages of: "this guru says this, this zen master says that" stuff,
.

I smiled at that.

Actually while philosophically Im in the "Dont tell me the answer -show me the reason camp"

Some days I just take the dumb and easy path and go with the guy with the grey hair and track record

[/quote]
Agreed... Experience counts.. A LOT! Just that the folklore gets diluted sometimes, it gets crazy.

If the OP is comfortable test-assembling/measuring/pull apart/shimming... cool. If he's more inclined to simply replace worn parts, keeping it as it was, ball may be a better choice. This is simply based on countless threads of "shimming drama" :lol:
Despite the great OldBritts how-to article. :shock:

B+Bogus · Apr 22, 2014

johnm said:
Some days I just take the dumb and easy path and go with the guy with the grey hair and track record

Agreed, Grasshopper.

I have trodden both paths, and the path of shims and Superblends leads to bad kickstart Karma as it can reduce the splined area.

The 'Hemmings' High capacity ballrace is closer to Shangri-La.

Layshaft bearing choice

Oakland850

Torontonian

concours

johnm

concours

B+Bogus

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