Lay Shaft Bearings?

calbigbird · Sep 6, 2009

I read on an earlier post about problems with the lay shaft bearings. As I recall, movement of the kick starter could be an indication of a pending problem. It seems to me I recall that problem being with pre MkIII models for the most part.

I noticed my kick start lever moving counter clockwise a bit when I pulled up the driveway into the garage tonight. I have a MK III, but I don't know the history of the transmission. Should I be suspicious of the lay shaft bearing?

bigstu · Sep 7, 2009

If your kickstart starts to move anti-clockwise under acceleration this is a sign that your layshaft bearing has radial play in it.
I replaced the ball bearing in the back of the gearbox with a lipped roller bearing. This is apparently a common upgrade which improves the load bearing capacity of the layshaft.

calbigbird · Sep 21, 2009

The kick start lever on my MK III is definately moving "anti-clockwise" when the transmission is hot. I took it to a mechanic today who told me he has never had to repair this on a MK III. He is going to take it apart and see what he can find. I'll keep those with MK III models posted. More to come.

ILLF8ED · Sep 21, 2009

Hi Calbigbird,

I can't think of a reason the MkIII gearbox would be exempt from layshaft bearing failure. It has the same internal bearings as all Commandos. If your mechanic is going in there, it doesn't make sense not to replace the bearing in light of the fact you said the kickstart is acting up.

comnoz · Sep 22, 2009

The layshaft bearing on my MK3 failed and locked up the rear wheel at about 12,000 miles. Many years ago. This was my first experiance with the problem. It was on an interstate entrance ramp at around 70 mph and I kept it upright down to about 10 mph and then it highsided me. I won't forget that one and I will not ride another Commando until I have put a roller bearing in that position. Jim

Flo · Sep 22, 2009

Probably a weak kickstart spring that has not been put on properly.

79x100 · Sep 22, 2009

Mk111s in the UK had the 22T sprocket and had probably the most problems with the layshaft bearing. I seem to recall a change to lower cost Portugese bearings didn't help ?

The symptoms are almost 100% certain and the cost of replacement at this stage shouldn't be high. If you wait for total failure then the complete box could be scrap and as Jim points out, sudden lock-up is a very real risk.

swooshdave · Sep 22, 2009

Flo said:
Probably a weak kickstart spring that has not been put on properly.

Wait, what? If it's exhibiting the classic signs of a failing bearing (with potentially disastrous ramifications) it's not prudent to propose less likely scenarios without additional facts.

L.A.B. · Sep 22, 2009

I would strongly urge anyone who happens to find they have a standard steel (or brass) caged layshaft ball bearing in their gearbox, to replace it with the (correct) single lipped inner race roller bearing (or Hemmings phenolic cage FAG ball bearing) without giving it a second thought, expecially if the kickstart lever is moving, as not only could it avoid a wrecked gearbox, but could also save your life!

_____________________________________________

Flo said:
Probably a weak kickstart spring that has not been put on properly.

Your photo shows that the layshaft is fitted with a roller bearing, and not the normal type that has the rollers & cage held captive in the outer race.

Flo · Sep 22, 2009

I replaced that bearing in the photo with a ball race from Mick Hemmings, as the inner race was rough.
No fun when it goes at 70mph two up. Been there, done that, got the new gearbox.
It is the one thing that should be replaced at the first oppertunity.
It is easy to feel if the kickstart spring it soft though. I was typing up more, but the post went wrong & I had to redo it, & my evening meal was ready at the same time.
Use either the special ball race or the roller, but not a standard one.

splatt · Sep 23, 2009

Flo, the bearing in your pic isnt correct is it :?: because the rollers should stay in the outer race, with the inner race on the layshaft. Different manufacture or different spec :?:

Flo · Sep 23, 2009

Havn't got a clue. It was sold to me years ago by a chap that did a lot of motorcycle engineering & racing. He informed me that it was the one they put in Norton gearboxes. I can't see that it matters if the rollers are captive in the inner or outer race, still a split roller. Has taken a hammering over the years.

calbigbird · Sep 23, 2009

Wellll??? Being El Cheapo, my bike is at a friend's (who knows what he is doing) getting all new bushings and new lay shaft bearing. I hate surpises! Sounds like parts will be a bit over $100.00 and labor is what it is. At least I have my new Goldwing to ride until the Commando is done.

BrianK · Sep 23, 2009

Is that Mick Hemmings-recommended ball bearing available from any US suppliers?

L.A.B. · Sep 23, 2009

BrianK said:
Is that Mick Hemmings-recommended ball bearing available from any US suppliers?

FAG ball bearing 6203 TB (P63?).

BrianK · Sep 23, 2009

Thanks Les

2ndchildhood · Sep 23, 2009

BrianK said:
Is that Mick Hemmings-recommended ball bearing available from any US suppliers?

I looked all over and couldn't find a supplier in the US. I finally just faxed an order to Mick Hemmings.

Lay Shaft Bearings?

calbigbird

bigstu

calbigbird

ILLF8ED

comnoz

Flo

79x100

swooshdave

L.A.B.

Moderator

Flo

splatt

Flo

calbigbird

BrianK

L.A.B.

Moderator

BrianK

2ndchildhood

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