Mick Hemmings Special Lay shaft Ball Bearing PN#?

MarshalNorton · Oct 24, 2009

Does any one know the correct bearing number on this layshaft bearing?
I'm going into my gear box this winter to correct a leak.
While in there ,I'm going to try to do the layshaft bearing only while box is still fitted in place.
Can map gas get the surrounding area hot enough for pulling the bearing w/ a bearing puller?
Id like to use Micks rcommended bearing as the way I understand the installation it is just a bearing swap.
It's a Sunday rider no track racing anticipated
Thanks,
Marshal

comnoz · Oct 24, 2009

NU203E.TVP2 The suffix is a FAG spec. There are several equivalents. Jim

MarshalNorton · Oct 24, 2009

Jim,
thanks for providing the part number.
Can I get it at a bearing distributor?
Also am I right that I can do a simple swap w/o shimming involved?
Marshal

comnoz · Oct 24, 2009

No shimming is involved. Just make sure the bearing from the bearing supply store has a shoulder on one end of the inner race. The race should come out of the bearing in one direction but not the other. Jim

L.A.B. · Oct 25, 2009

comnoz said:
NU203E.TVP2

THAT IS NOT THE MICK HEMMINGS BALL BEARING

That's the two piece roller bearing. [Edit] The correct single lipped inner race roller bearing is NJ203E...

The Mick Hemmings special phenolic cage ball bearing is a FAG 6203TB

Mick Hemmings Special Lay shaft Ball Bearing PN#?

MarshalNorton said:
While in there ,I'm going to try to do the layshaft bearing only while box is still fitted in place.
Can map gas get the surrounding area hot enough for pulling the bearing w/ a bearing puller?
Id like to use Micks rcommended bearing as the way I understand the installation it is just a bearing swap.

If it's still got an original ball bearing in there, once the case is hot enough the bearing will probably come out on the end of the layshaft, and yes MAPP gas will be hot enough.

MarshalNorton · Oct 25, 2009

Jim/L.A.B,
thanks for your responses.
Can I get the gear sets out and out of the way and then heat the box on the inside around the lay bearing and shaft ?
If shaft comes out then I'll heat and pull remaining part of old bearing out.
When the shaft and bearing come out as one unit do I heat the shaft and dislodge the bearing?
Thanks,
Marshal

L.A.B. · Oct 25, 2009

MarshalNorton said:
Can I get the gear sets out and out of the way and then heat the box on the inside around the lay bearing and shaft ?

If the layshaft is a reasonably tight fit in the bearing, then that can be useful so don't try to remove it. Gently pull on the layshaft as you heat the case, when it's hot enough the layshaft should then pull the bearing out quite easily? Use the layshaft to refit the new bearing once the case has been re-heated, the new bearing should go in very easily if the case is hot enough.

MarshalNorton said:
When the shaft and bearing come out as one unit do I heat the shaft and dislodge the bearing?

No, just tap (or lever) the bearing off the end of the shaft.

I know Mick Hemmings and John Hudson always recommended that the bearing shouldn't be a tight fit on the end of the layshaft, and to 'emery tape' the end of the shaft down until it is a light push fit in the bearing.

L.A.B. · Oct 25, 2009

MarshalNorton said:
Can I get the gear sets out and out of the way

Yes, although layshaft 3rd. and 4th. gear pinions will be held captive by the shaft until it is removed.

comnoz · Oct 25, 2009

Your right, it's the roller bearing, one step up from the ball bearing. Came from TC's heavy duty kit around 20 years ago. And it was polymid caged. And it's still in my bike close to 100,000 miles later. Jim

L.A.B. · Oct 25, 2009

comnoz said:
it's the roller bearing, one step up from the ball bearing.

Well..I know Mick's recommendation is the 6203TB ball bearing over a roller.

comnoz · Oct 25, 2009

Well I am not sure why unless it was price. The roller has much higher load carrying capacity. It's basically the "superblend" version of the ball it replaces. I would suspect either one has enough load carring capacity for normal use. I have always used the roller. Jim

L.A.B. · Oct 25, 2009

comnoz said:
Well I am not sure why unless it was price. The roller has much higher load carrying capacity. It's basically the "superblend" version of the ball it replaces. I would suspect either one has enough load carring capacity for normal use. I have always used the roller. Jim

Mick's own words from his Gearbox Servicing NOC DVD as he discusses the layshaft bearings:

"...now, roller bearings are OK, but, what I don't like is that they can support vertically but they won't take any end load, and there's a lot of end-thrust on a gearbox -especially when you are pushing it into gear. The bearing that I prefer [showing the ball bearing] is a very very special ball bearing, I've been using this for twenty years, and it's been used by everybody from Wayne Gardner to Barry Sheene in all the six-speed gearboxes I build, and 'touch wood' we've never had a failure yet, so that is the bearing that I prefer to use...."

Mick goes on to say there's nothing wrong with using a ball bearing, just that the cages break up, and that is the reason he uses the special ball bearing with the phenolic cage.

comnoz · Oct 25, 2009

I would agree with the fact that the original bearings failed because the cages broke up. But neither bearing is rated for thrust loads.

L.A.B. · Oct 25, 2009

comnoz said:
But neither bearing is rated for thrust loads.

True, however, I would have thought that a deep groove ball bearing would be better suited to cope with any side thrust loading than a roller? After all, the '71-on Commando steering bearings are nothing more than deep groove balls which must be constanlty subjected to side thrust, but generally do not give any trouble?

Rich_j · Oct 25, 2009

comnoz said:
I would agree with the fact that the original bearings failed because the cages broke up. But neither bearing is rated for thrust loads.

True, roller bearings generally have no thrust capability but deep groove ball bearings certainly do, obviously not as much as some other types but its all published in the bearing handbooks and the bearings are not being misused.

comnoz · Oct 25, 2009

The only thrust applied to the layshaft is what is created by the drag of the gear on it's splines as it is being moved from one position to the next. Either bearing has plenty of thrust capability to handle this. I will stay with the extra load capacity of the roller even if it is overkill. I have removed ball bearings with brinelling in the races from wear and I have yet to see this on a roller. Jim

comnoz · Oct 25, 2009

And by the way, the original spec for the steering head bearings was for an offset groove type ball bearing that was designed for thrust loads. {at four times the cost] And the isolastic rubbers were originally expanded stainless steel spring bushings. Both were nixed by the beancounters when design went to production. Jim

Rich_j · Oct 25, 2009

comnoz said:
And by the way, the original spec for the steering head bearings was for an offset groove type ball bearing that was designed for thrust loads. {at four times the cost] And the isolastic rubbers were originally expanded stainless steel spring bushings. Both were nixed by the beancounters when design went to production. Jim

Looks like the bean counters got it right for once

comnoz · Oct 25, 2009

At least they got by with it.

L.A.B. · Oct 25, 2009

comnoz said:
And it's still in my bike close to 100,000 miles later.

Well...if my 6203TB ball bearing only makes it to half that distance (or less?).....then I'm never going to need to change it!

Mick Hemmings Special Lay shaft Ball Bearing PN#?

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