Finnaly getting to the Layshaft bearing. Question.

I finally have time to look into my Layshaft bearing and just wondering if it is possible to check and change one without removing the primary and clutch to heat the back side. Can this be done or not? Going to take the bike on a trip soon so and don't feel safe not knowing about the bearing but don't have time to go deeper into dissasembly then I have to.

Probably depends on how hard it is to get it out. The two I have done both required heat and a puller and I had the case out of the bike. I suppose it could be done, but it may be a challenge.

Dave
69S

As DT says, it can be done but it's not really a very nice way to do it. It will be very difficult to get everything really clean and there will be no possibility of properly checking the sleeve gear bushes and replacing the oil seal (which I would do as a matter of course). Dropping the new bearing in, according to approved practice will also be hit and miss.

If you do go ahead on this basis and then find that the box has to come out, you'll wish that you had loosened the engine sprocket and clutch nuts whilst everything was still together.

I'm going to risk being shot down in flames here but in my opinion, the secret to trouble-free Commando ownership is to take every possible opportunity to double check everything - which of course is exactly what a dealer can't do - and therefore probably gives a good clue as to why they often gave so much trouble in the era of dealer servicing.

If you have access to a automotive clutch pilot bearing puller with a slide hammer they are easy to do in the bike. Without that they sometimes are pretty tough. A heat gun to heat the housing and a couple small picks may pull it out. Do not use a small prybare or pick and apply pressure to the aluminum housing behind the bearing as the case is very thin in that area. Don't ask how I learned that. Jim

Yes the whole gear box can be serviced in place, so yes bearings can be removed and new fitted w/o easing the job by removing shell on work bench.
Hair drier would be safer than torch and likely heat quicker and better covering more area than wimpy torch unless the kind Mr. Hudson used to set his bench on fire in his instruction video.
A welding rod tacked to the bearing race would suck it right out but may not heat case up enough to put one right back in time.
Might consider an order of super magnets to suck out the blind bearing race or some inside wedgie device or epoxy a handle on before the heat help. Can't hardly over heat them shells. I've had to get to frying pan hot to get a lodged race to bump out with lots of hard slamming on wood block.
So yes in principle, it should all work out slick and easy, unless it don't like mine.

I've personally come to the conclusion its less strain to just mediate the tedium to pull everything out in the open than suffer the head bowed Norton worship posture. Often uncover other things you might have missed spending on too.

hobot

The box usually needs to be hotter than a hair dryer to release the bearing. About 300-350 degrees. About the time it will sizzle when you touch it with a wet finger. A torch is hard to control and can damage the aluminum. A hot air gun like used to lift tile works great. Jim

H.B.N.W.P. ( Head bowed Norton Worship Posture) been there before. My main reason for not wanting to go to deep is that I think the bearing may have allready been changed but can't know for sure. The PO put 73,000 well maintained freeway miles on this bike!! I know the engine has been apart & have a hard time thinking this layshaft bearing is still the orig one. It all shifts smooth and doesn't leak a drop. I really just want to go in to know for sure, other wise I would not hesitate to take everything apart.

79x100 said:

It will be very difficult to get everything really clean

Click to expand...

I'm not entirely sure what would need cleaning inside the gearbox?

79x100 said:

Dropping the new bearing in, according to approved practice will also be hit and miss.

Click to expand...

I'm not sure I entirely agree approved practice dictates the layshaft bearing must be dropped in? As the new bearing can simply be inserted using the layshaft as the fitting tool. If the case is sufficiently hot enough (and it shouldn't need to be that hot) then the bearing should "drop" in easily when inserted with the layshaft, that's how I do it, and that's how Mick Hemmings does it in his gearbox rebuild video with the gearbox 'out', so if it's good enough for Mick....

The photo shows how far you'd get without removing the mainshaft so there's enough room to get a torch in to heat the case. If you pull on the layshaft and it doesn't want to come out when the casing is cold, then it's almost certain there's a ball bearing behind it, so don't try to extract the layshaft, because once the casing is hot enough then the bearing should come out on the end of the shaft.

gtsun said:

H.B.N.W.P. ( Head bowed Norton Worship Posture) been there before. My main reason for not wanting to go to deep is that I think the bearing may have allready been changed but can't know for sure. The PO put 73,000 well maintained freeway miles on this bike!! I know the engine has been apart & have a hard time thinking this layshaft bearing is still the orig one. It all shifts smooth and doesn't leak a drop. I really just want to go in to know for sure, other wise I would not hesitate to take everything apart.

Click to expand...

With that many miles on the bike and you know the engine has been into, I'd probably not worry about the bearing. Just worry about all the other things before your trip.

Putting the bearing in is easy.
Keep in mind if you use a torch that the gear teeth start to loose the case hardness at about 500 degrees F. It is easy to exceed that temp with a torch and a thin tooth. Jim

Maybe I'm just being over fussy L.A.B, but I've never opened up a well-used Commando box and not found some evidence of goldish particles and shiny flakes in it. Personally, I'm happier flushing the whole thing out with bearings removed.

In terms of 'dropping ' the bearing in, I prefer to let gravity do the work leaving me to just listen for the 'clunk' . I'd always understood that to be the preferred way. Mick Hemmings can obviously do AMC boxes blindfolded after a drinking session and knows just how hot to get them but I'd fear that an inexperienced hand is quite likely to force things if using the layshaft as a mandrel.

Burned knuckles ? Who ? Me ?

The sideways lay shaft insertion method does have advantage of the shaft helping the bearing stay cool-smaller longer to get seated well. BUT also means if not held till Al surround grabs it - it can come right back out with the lay shaft or worse get hung up cockeyes and clamped, often on quick second attempt to replace while still expanded enough, but ain't. I prefer to know the clunk of free drop in was complete by a rap by drift or lay shaft. Parts vary enough what some get away with other cases can't.

hobot

As far as "dropping" bearings in, I "dropped" the crank case bearings in and heard them clunk, but when I test fitted the crank, it was tight. I had to heat the timing side back up and drift it in a few of thou. It is real nice if you have a outdoor gas grill to heat the cases in, I have a small one and it has a temp gauge too, so that was nice.

Dave
69S

Well there ya go, its by fate alone whether things work out as in manual or ideal.
I count a jammed bearing in rapidly cooling case as cause for a pause into another,
< Blank stare dropped faced uncomprehending denial recoil state>

I am so seasoned on this stuff now knowing what I'm in for, what it takes to deal with Combats, real reason i'm poking my noise in others business is to suck on everyone else's confidence as they advise you innocently into Norton's countless opportunities to screw up again.

I find that when working on a NORTON you need to put rideing out of your mind and not take shortcuts to do the fix our youll be doing it over Having said that I did my 74 back in76 on the bike with an industrial heat gun and a otc1173 slide hammer puller Took it apart this year bearing was still good but had some bad bushings Phil

Thanks for all your advice gentelmen. I think I will go into it & see how it goes. If it turns out to need more work and I don't have time I'll be running around Sequoia national on my BSA instead!