Layshaft Bearing Question(s)

Well, it happened, the layshaft bearing on my MKIII bit the dust. I don't
know if it was the original bearing or not, it was stamped in three spots,
1) FAG; 2) 6203, and 3) A P. Could this be the Portugal bearing?

What I found was that the cage was almost completely gone, I found two tiny remnants of the
cage in the bottom of the case. Inner race came out with the layshaft, and was a very tight fit.
Eight (8) ball bearings fell to the bottom of the case, when I removed the layshaft.
The outer race stayed partially in the case, but could be removed by hand without
heat.

The new bearing (FAG 6203TB/C3) is a firm push fit into the bore, once again without
heat. After reading through all the layshaft bearing threads I could find, I believe the interference fit is
not as tight as it should be. So, I've decided to use a smear of JB Weld to hold it in place, as recommended
by hobot and Comnoz in various threads.

hobot said:

While on subject I've yet to hear a single success story of any type loctite holding a bush or bearing stable, nuts and fasterners yes, me too, but not in tranny or engines, ever. Jim Comstock verified my idea to use |JBWeld in loose bores.
Hi heat OVER 500' F will soften it to cold honey state. Al don't loose its intergrity till close to 1000 F and nil distortion if whole case heated instead of just spots.

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comnoz said:

I think if it was mine I would use a very light layer of JB weld in the bore before you push the bearing in. Will not likely give any trouble. Jim

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I guess my first and main questions for now would be…
1) Should I scuff the bore and outer race to give the JB Weld a better surface to grip on?
2) Should I just use a thin smear of JBW or a slightly thicker layer to fill the gap when I heat the case?
3) Should I even use heat, or just push it in by hand?

The Portugal bearing had "Portugal" stamped on it.
I wouldn't scuff, you have an interferance fit as it is, no need to reduce it further. I think making sure the surfaces are clean is more important.

Again, since you have an interferance fit, a light smear should be fine. I would apply the JB to the bearing as to not cause a build up behind the bearing when pushed in, then clean up along the edge.

I think my advice is sound but I would still play it safe and wait for further opinions.

I would clean it up with no residue solvent and fit the new bearing with a thin coat of JB weld. I usually have put it in the bore but as Pete says only a very thin coat so it doesn't get a buildup behind the bearing. A thin coat on the OD of the bearing also couldn't hurt anything.
It sounds like the bearing you took out was a replacement bearing. I have seen the replacement ball bearings fail like the Portuguese original if they have a riveted steel cage. I would avoid a riveted cage bearing. Jim

One other thing worth considering is fitting sealed bearings and leaving the seals fitted, sealed bearings will be protected from the crud in the oil, the oil will still be able to cool the bearings from contact to the cases.

Will also protect the gear box if the bearings disintergrate in the future.

2Wheels said:

1) FAG; 2) 6203, and 3) A P. Could this be the Portugal bearing?

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Original Portuguese or not, it seems to be the same type as the (brass cage) bearing I removed from my Mk 3.

Your picture makes me correct what I said about riveted cages. [Brain fart]
It is the cage with the folded tangs such as the one in LAB's picture that tend to come apart. The ones with the rivets between the balls or a plastic or machined bronze cages seem to work well. Jim

Question: doesnt the bearing spinning cause or at least contribute to
the crack in the tiny web twixt the layshaft bearing and the sleeve
bearing? If the layshaft is a loose fit isnt the sleeve going to be
in need of potting too?
Aren't you the one who posted the pix of securing the bearing
with a washer? Seems like a much better way than glue.

Onder said:

Question: doesnt the bearing spinning cause or at least contribute to
the crack in the tiny web twixt the layshaft bearing and the sleeve
bearing? If the layshaft is a loose fit isnt the sleeve going to be
in need of potting too?
Aren't you the one who posted the pix of securing the bearing
with a washer? Seems like a much better way than glue.

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It was not I that posted about the screw to hold the bearing in place. From what I have seen the crack between bores is usually caused by a failed bearing or a broken layshaft.
It is common for the bearing to float around and turn a bit even in a tight case when things get hot. I have indexed the layshaft bearing on installation and found they were not in the same place when I took them apart. Main bearings do the same thing only more.
The only sure way to keep them in place is a screw and washer. I have installed a few with JB weld but I don't know yet if they held. Jim

I'm holding me breath until you Twingle test then check on the JBWeld filler.
I'd sure appreciate some hand holding on how you got such bearing risky stuff
in such thin area w/o excess in the way. Was bearing rough texture done?

hobot said:

I'm holding me breath until you Twingle test then check on the JBWeld filler.
I'd sure appreciate some hand holding on how you got such bearing risky stuff
in such thin area w/o excess in the way. Was bearing rough texture done?

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Just cleaned with scotchbrite and lacquer thinner and wiped on [the bearing only since the case was hot] with my finger as thin as I could get it. Hopefully I will not be taking the twingle apart for a few years to see if the bearings have moved.
If they have it is not a big deal. I have not disassembled a motor yet that does not show signs that the bearings have been rotating except when they were locked in place with a screw and washer. Jim

What about using bearing locker ?, there are many brands of the product, designed to do exactly what you are wanting, usually rated to hold a bearing into a 5 thou gap.

http://www.loctite.co.uk/cps/rde/xchg/h ... n-4371.htm a specific bearing retaining product is likely to work far better than a cheap filled epoxy. In the case of shafts that are very badly worn, its sometimes possible to reclaim them with something like Loctite 660, which can deal with quite high levels of wear/damage.

Locktite bearing mount was what I tried first. Made absolutely no difference on the layshaft bearing or main bearings. All signs of the locktie were gone except what was trapped in the radius and the bearings had rotated. Jim

Now you are at it ditch the ball bearing and use a superior roller bearing with E specification (like the superblend 306E crankshaft roller bearing, this type roller bearing with 'E' specification has 'rounded edges' to cope with flexing shafts). For example a FAG NJ203E layshaft bearing will take far more load then any other ball bearing (or roller bearing without E specification), provides easy removal of the layshaft/gears and some (possible) side float of the layshaft/gears for smooth engagement.

comnoz said:

Locktite bearing mount was what I tried first. Made absolutely no difference on the layshaft bearing or main bearings. All signs of the locktie were gone except what was trapped in the radius and the bearings had rotated. Jim

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Bearing fit is unlikely to work if there is appreciable wear/distortion, in these cases something like Loctite 660 is more suitable. However if the bearing register itself is badly out of round, then re-machining the housing and sleeving may be the only solution. Years ago when working in a bike shop who raced Norton MX sidecar outfits, gearbox bearing problems were very common, and in general the damaged cases were simply replaced.

comnoz said:

Locktite bearing mount was what I tried first. Made absolutely no difference on the layshaft bearing or main bearings.

Click to expand...

Jim - which Loctite did you use? I had a comprehensive training a few years ago and it was pretty impressive to see how much influence the correct grade and precise preparation had. E.g. there is a huge difference between using normal brake cleaner and the proper Loctite cleaner in terms of bond strength - before I saw the evidence that stuff always had a certain smell of comercialism to me. Then there is Loctite formula which are oil tolerant - probably very nice when working on Britiron.

Best regards,


Tim

Tintin said:

comnoz said:

Locktite bearing mount was what I tried first. Made absolutely no difference on the layshaft bearing or main bearings.

Click to expand...

Jim - which Loctite did you use? I had a comprehensive training a few years ago and it was pretty impressive to see how much influence the correct grade and precise preparation had. E.g. there is a huge difference between using normal brake cleaner and the proper Loctite cleaner in terms of bond strength - before I saw the evidence that stuff always had a certain smell of comercialism to me. Then there is Loctite formula which are oil tolerant - probably very nice when working on Britiron.

Best regards,


Tim

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I don't have the part number but it was locktite stud and bearing mount used with locktite primer. My main objective was to keep main bearings from rotating in the engine case without doing the Dunstall bolt and washer modification. I had noticed the polishing and scratches in the outer race of bearings I had removed from normal street going engines and had made a point of installing all of the bearings in the same position [ie part number closest to the timing pinion]
I found that even in cases with a good tight fitting bearing the bearings would not be in the same position even after a short time running.
I even went as far as using .0015 shim stock under the bearing to increase the pinch on the bearing. The superblend C3 bearing became very difficult to assemble as the clearance would go away and yet the bearing would rotate in normal use. [and would show no signs of distress from the too tight clearance]
The locktite made no difference and I doubt that the JB weld will either although I must say I have had better results using JB weld to keep bushings like the two piece cam bushing from coming loose.
The fact that the bearing rotates in use does not seem to bother anything very much. The wear from rotation occurs on the bearing more than the case as the oxides get embedded in the soft aluminum and wear the hard bearing surface. You can always tell how many miles are on a main bearing by observing the outside and seeing how much of the surface is polished. The grinding marks from manufacture will disappear starting at the edges and then progress eventually all the way across the bearing. Eventually all that is left is a polished surface with tiny scratches in line with the rotation. All of the diagonal hone marks will be worn away.
A countershaft bearing will rotate in a tight case also but I suspect it requires hard use to get the case hot enough to release its grip. I have tried locktite there also but found the race would be moved after use. I have only checked the coutershaft bearing on my racebikes.