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G: Gearbox Sealed or unsealed gearbox bearings

Rob H

Well Known and Active Website User
VOC Member
I have noticed that the spares company offer rubber sealed G14 and E91 gearbox bearings, I am guessing as a means of eliminating dirt or oil leaking out.

This type of bearing is pre greased. When in use would you remove the inner seal to let the gearbox oil access or better to keep sealed?

Any views, advantages/disadvantages on their use?
 

greg brillus

Well Known and Active Website User
VOC Member
No real problem using them, I generally leave the inner seal out so the bearing gets lube from the rotating parts.........They do not really stop oil passing through, better than nothing when used on the E 91 crank main bearing, but as is known, the width of the inner race is usually narrow and has less contact area for the sprocket inner face to bare on....... I use a hardened washer there to help. My guess is that sealed bearings are just more common now than the ones from years ago, just like the use of "O" rings now........You still need to make sure the bearings have the C3 clearance, using standard clearance bearings is risky, as they tend to run too tight, with their radial clearance taken up once the heated cases cool down. Always check to see the inner race spins freely after installation...........Cheers.
 

Normski

Well Known and Active Website User
VOC Member
No real problem using them, I generally leave the inner seal out so the bearing gets lube from the rotating parts.........They do not really stop oil passing through, better than nothing when used on the E 91 crank main bearing, but as is known, the width of the inner race is usually narrow and has less contact area for the sprocket inner face to bare on....... I use a hardened washer there to help. My guess is that sealed bearings are just more common now than the ones from years ago, just like the use of "O" rings now........You still need to make sure the bearings have the C3 clearance, using standard clearance bearings is risky, as they tend to run too tight, with their radial clearance taken up once the heated cases cool down. Always check to see the inner race spins freely after installation...........Cheers.
Greg I’m interested in the hardened washer you use against the sprocket, I seem to need a c. 20 thou spacer between the sprocket and the bearing to get good primary chain alignment and am worried that the movement as the esa works will eat away at something not hard enough. Or have I got this wrong? There is some wear on this face of the sprocket so I may also be able to gain the 20 thou by using a new sprocket, your input would be appreciated.
 

greg brillus

Well Known and Active Website User
VOC Member
Yes the shim washer should be hard, E 76 washers if they are hard enough will do........30 to 40 odd thou thickness, no thinner. The chain alignment can go out a bit, but you can also shim the clutch assembly out a small amount to compensate if necessary. A sealed bearing on the crank end will slow the migration of oil.......some engines it works fine others not so much......Probably depends on the state of the engine and how hard it is pushed........Of course a proper lipped seal is best, but quite a bit more trouble and possible expense to carry out.
 

Rob H

Well Known and Active Website User
VOC Member
Greg, are you saying that all the bearings should be C3 or just the E91 outer crank bearing.

I have checked the original bearings that were in the cases but none were marked C3. It looks like they were just the standard CN
 

oexing

Well Known and Active Website User
VOC Member
With motorbike engines I never cared about C 3 bearing types. Keep in mind the bearings sit in alu cases so when at operating temperatures they are almost loose or even spinning in the bores with wear in consequence. So really they may be a bit tight with a cold engine but who drives a cold engine, not very long. Remember any Velocette got a preload when cold with their taper roller mains else you´d get sloppy crankshaft when all expands. So that cold preload does not hurt taper or cylinder roller bearings at all. Only matter is you may have to warm the case when assembling all internals , no bad practice anyway.
Sealed bearings may be used as they come, even with oil fill in engine. One could discuss what´s worse to bearings, lifetime clean grease filling - or contaminated engine oil ?? Most likely the grease will last better for thousands of hours than with dirt loaded engine or gearbox oil.
The poorly designed sprocket steel bush plus ESA springs preload onto sprocket acting on the inner race may be improved with a top hat steel bush for getting a lot more of space spreading forces from springs and reducing wear on the inner mainbearing race and sprocket . This can look a bit like in my photo, when you face turn the (ball) bearing inner race till the radius is gone mostly. So the gained space will be filled with the top hat bush for longer use.

Vic
P1070540.JPG


P1070535.JPG
 

greg brillus

Well Known and Active Website User
VOC Member
Well I've removed enough standard clearance bearings that to me are tight to rotate, and feel rough. Some folk have no mechanical sympathy and are happy to start an engine from cold and thrash it down the road......... So how should a manufacturer ensure that the engine parts can survive this abuse.........By allowing enough running clearance to not allow it to self destruct.........Many times i have installed the ET 94 small timing side roller bearing in a heated case, and the inner race will not enter without force........thus requiring the outer race to be honed oversize......... Most folk would simply live with it, and assemble it up and hope for the best.......it may or may not give trouble........That is the gamble one must take........I am not a gambling man, so i make sure it "is right" so i don't have to walk away wondering...........
 

Rob H

Well Known and Active Website User
VOC Member
Interesting debate, at the moment just looking at the bearings for the gearbox, now not sure what to get.

Anyone know what the VOC Spares Club sell?
 

oexing

Well Known and Active Website User
VOC Member
Well yes, Greg, in those cases when you cannot slip a crank in its place even with a heated engine the bearing fits must be wrong. So somebody must have machined not to specification for proper fits. It pays to measure up ALL parts for exact sizes else you end up with overly tight fits - or staking to prevent races from dropping out in heated case . Seems you have to be prepared for all sorts of defects with Vincent engines - even in factory new conditions it seems. But then, even a C3 will not be allright with this in times.
Thrashing a cold engine may not be great for a tight bearing but my guess the bearing will be your smallest problem , you´d get some bigger problems in other places in no time. So what to think about preloaded taper bearings on Velocettes in cold condition, same question there ? I would not be so nervous about minor tightness in cold condition when in operating condition it is free, any lathe runs preloaded taper roller bearings all times for rigidness. You just check for a max. temperature at max. revs there for setting preload.
With the small outer roller bearing on timing side some "roughness" may be due to the cutout for the pump worm and this may be reason for out of round outer race when shrink fitted, so some feel of roughness - or so Vincent Speet told me. I am not clear about correct machining procedures of oil pump housing and boring main bearing fits and minor distortions from this with out of round effect from this.

Vic

Vic
 

greg brillus

Well Known and Active Website User
VOC Member
Rob just use the normal open bearings.........on a standard engine with good bores and piston rings you do not need anything else. The use of sealed bearings in the gearbox is a waist of time, just use one to 1.1 liters of 80 w 90 gear oil in there. Bearing failures in these engines are usually due to some kind of mechanical failure........either the race has been punch locked into the case, or loctite used with heat this creates too much radial crush on the race and it becomes too tight to rotate. Excessive punch locking distorts the outer bearing race so much that it makes the bearing feel like a ratchet when you rotate it......The mains come loose due to poor crankshaft alignment.........usually found in engines that have had a hard life.........thrashed in other words......
 

greg brillus

Well Known and Active Website User
VOC Member
Should be C3 bearings....... If the gearbox bearings come out without any heat, then it would be ok to use standard bearings with the application of a loctite product.........In a gearbox you can get away with this, but a hammering load like a crankshaft I would not recommend it.
 

Rob H

Well Known and Active Website User
VOC Member
Just spoke with the Spares Co, they confirmed that the gearbox output shaft bearings (G14, E91) they sell are C3, however the smaller layshaft bearings G15 are standard clearance.
 

greg brillus

Well Known and Active Website User
VOC Member
Probably unavailable anymore.........I have removed some from cases that have been stiff to rotate, but they could have been put in with loctite as well..........need to be careful using that stuff at times........Nice to measure the bearing bores accurately first if possible.
 

Rob H

Well Known and Active Website User
VOC Member
Probably unavailable anymore.........I have removed some from cases that have been stiff to rotate, but they could have been put in with loctite as well..........need to be careful using that stuff at times........Nice to measure the bearing bores accurately first if possible.

No they still are available!
 

greg brillus

Well Known and Active Website User
VOC Member
Ok that's good, well the smaller bearings seem to suffer the outer race contracting more as the case cools down.........The timing side small main bearing is a bugger for that happening.
 

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