Gear box bearings

Ive got to the stage with my bike that its been half together and back into very small bits again (falling off the bench in an earthqauke didnt help). Ive got the motor side almost sorted so its time to look at the gearbox, or specificly what bearings should I be putting in?

Im guessing that there are two roller bearings (main and lay shaft) and then a ball in the cover? or is this a roller bearing as well? does anyone have the numbers of the preferred bearings?

Thanks

Cheesy said:

Im guessing that there are two roller bearings (main and lay shaft) and then a ball in the cover? or is this a roller bearing as well? does anyone have the numbers of the preferred bearings?

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The D/S sleeve gear and layshaft bearings were both ball bearings originally, the layshaft bearing should be replaced with the NJ203 roller, or the Mick Hemmings FAG 6203TB poly cage ball bearing.

Commando bearing list: http://www.nocnsw.org.au/bearings.html

L.A.B.

Did the factory ever catch on and upgrade the layshaft bearing? If so do you know the year or serial number cut-off?

RS

RoadScholar said:

Did the factory ever catch on and upgrade the layshaft bearing? If so do you know the year or serial number cut-off?

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It seems doubtful that the factory ever fitted the layshaft roller bearing as a standard part judging by the number of Mk3 gearboxes found to have a 6203 ball bearing in them (my own included).

Possibly Andover Norton has a record of when they started supplying the NJ203 roller in place of the 6203 ball bearing?

Perhaps ZFD (Mr Andover Norton) could shed some light on this subject?

I just replaced my layshaft bearing with a fag 6302 tb.c3 ball bearing. No shimming required.
Cost at a local bearing house $32 US. Ride safe.

I have read the tale that Mk3s were supplied with roller layshaft bearing 06-7710, but from personal experience- my layshaft bearing on 335113 (my Mk3 Commando I bought new in 1977) failed (also in 1977!), and it was the infamous Portugese ball bearing 04-0100. I very much doubt roller bearings were ever fitted from new. My experience is limited- just over 3 decades in Commando spares- but I have yet to encounter a Commando that had the roller bearing from new. The remedy was known at the time, however, and I fitted the roller bearing and rode happily everafter- a total of over 30.000 miles if I remember correctly.
Joe Seifert

MIKEYG said:

I just replaced my layshaft bearing with a fag 6302 tb.c3 ball bearing. No shimming required.
Cost at a local bearing house $32 US. Ride safe.

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If shimming is not required with the ball bearing then no shimming will be required with the roller bearing. The choice of bearing type does not affect the need for shimming.
And yes I have read incorrect info to the contrary. Jim

The only layshaft shimming I've found to be necessary with roller or ball bearings is to actually shim the kickstart stub between the inner gearbox cover and the knuckle, which keeps the pawl end embedded within the layshaft first gear--the layshaft may float just a tad but the kickstart stub should have very little play in and out.


Tim Kraakevik
kraakevik@voyager.net
Two Commandos

kraakevik said:

The only layshaft shimming I've found to be necessary with roller or ball bearings is to actually shim the kickstart stub between the inner gearbox cover and the knuckle, which keeps the pawl end embedded within the layshaft first gear--the layshaft may float just a tad but the kickstart stub should have very little play in and out.


Tim Kraakevik
kraakevik@voyager.net
Two Commandos

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That is correct. And that is the shimming that has been said to be needed with roller bearings only. However that shimming needs to be done with any bearing choice and was being done by Norton dealers long before anyone ever thought of using a roller bearing on the layshaft. It also affects how far the first gear dogs engage so helps prevent jumping out of first gear. Jim

MIKEYG said:

I just replaced my layshaft bearing with a fag 6302 tb.c3 ball bearing. No shimming required.
Cost at a local bearing house $32 US. Ride safe.

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I am currently looking around & pricing both crank and layshaft bearings. The best price so far on mainshaft bearings is $130 for a pair of
FAG NJ306e.M1. C3. The box says it a German made FAG bering. I recently read about some counterfeiting going on in the bearing business, any chance of this being counterfeit?

I priced out the layshaft bearing # 6203TB @ Old Brits for $66. My two local bearing suppliers wanted $197, $174. Both of the parts guys stated that these wee presision bearing, henc the high price. Am I requesting prices for the correct number?