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Well one reason for my poor rear brake was oil on the shoes/drum along with a well glazed braking surface on the drum liner. Not huge amounts, but enough to make it all oil soaked. I picked up a new Hub oil seal with the brake pads yesterday that I can access from the brake side, but was advised by Cam Lam that the likely cause may be the lay shaft O ring.

Now before I launch into disassembling the clutch side of the motor to get the lay shaft out, I plan to fit the new oil seal and run the motor in gear for a while (on the stand/jack still on the bench) so I can see what's going on.

Is this the best/only way to test the lay shaft O ring? I don't want to reassemble and then find out the same's happened to the new brake shoes?

I'll make a mandrel to mount the drum and emery cloth the brake surface to de-glaze it - that's the easy bit!

Any advice welcome and no doubt more special Lambretta specific tools will be needed.

Thanks Folks..

You can often get a sense of where the oil is coming from by studying the area around the bearing, seal and layshaft. If you have now wiped this area down, then your idea of running the engine on the stand seems worth a go. How quickly oil leaks show themselves, I’m unsure.

In the past, I have just fixed what I thought the problem was, put it all back together, and then taken the hub off a couple of hundred miles later. You’ll then see if you have fixed it by close inspection of the area around the bearing.

Oil leaking around the outside of the bearing is often a cause too.

Storkfoot wrote:You can often get a sense of where the oil is coming from by studying the area around the bearing, seal and layshaft. If you have now wiped this area down, then your idea of running the engine on the stand seems worth a go. How quickly oil leaks show themselves, I’m unsure.

In the past, I have just fixed what I thought the problem was, put it all back together, and then taken the rub off a couple of hundred miles later. You’ll then see if you have fixed it by close inspection of the area around the bearing.

Oil leaking around the outside of the bearing is often a cause too.

Thanks Paul & will take note of your advice.

Storkfoot wrote:You can often get a sense of where the oil is coming from by studying the area around the bearing, seal and layshaft. If you have now wiped this area down, then your idea of running the engine on the stand seems worth a go. How quickly oil leaks show themselves, I’m unsure.

In the past, I have just fixed what I thought the problem was, put it all back together, and then taken the hub off a couple of hundred miles later. You’ll then see if you have fixed it by close inspection of the area around the bearing.

Oil leaking around the outside of the bearing is often a cause too.

+1

Well I think & hope it's good news. Stripped the lay shaft brake side of it's plates and cone, de-greased it all and ran the motor for a good 10 mins. Motor was running in 4th & I got it sort of warm, so not hot as such. No sign of any oil getting through, so will try Paul's suggestion next of a hundred mile road test and then disassemble to check it again. I didn't change the oil seal either, so it's as it was originally.

Also made a mandrel to mount the rear hub through the layshaft mount & skimmed the brake lining (0.25m per side) to remove the ovality that was in it. Also dressed the height of the brake lining so it was cleaned up parallel to the hub - this needed 1.5mm off. I was only planning to de-glaze the brake lining. but I could feel it was out of round so that would give less braking contact area and a pulsing pedal - had to sort it.

Rear Hub Mandrel 2 by KTM Marky, on Flickr

Rear Hub Mandrel 1 by KTM Marky, on Flickr

This is the original brake liner surface:

Rear Hub Liner Untouched by KTM Marky, on Flickr

Rear Hub Liner Dressing by KTM Marky, on Flickr

Dressed liner face:

Rear Hub Liner Dressed by KTM Marky, on Flickr

Before run up:

Rear Hub Running 2 by KTM Marky, on Flickr

After run up:

Rear Hub Running 1 by KTM Marky, on Flickr

Next job is the MB Scooters rear brake pedal hardware & to set up the brake shoes. Might even make a jig to hold the shoes in position to dress them too - should give the max braking surface area..

Has anyone tried gently presurising the chain case and checking for leaks with soapy water? obviously would need to blow in via a bung in the breather and maintain a positive air pressure as it will escape via the kickstart and other orifices....or as suggested, new oil seal, o ring and a smear of silicone around the bearing before fitting.

As Paul said, oil on the shoes is a common issue, Im just wondering if anyone has ever worn their rear shoes out

That brake cam looks like an Li type whereas your should be the GP variety, not realy an issue so long as the shoes match.

Check Steve Richards on Youtube (The Steel Weazel) he talking about the front but its all relevent to thye reav Part one deals with taking a file to the cam
https://www.youtube.com/watch?v=JboLYuGHC10

I am on record as stating that IMO the OEM layshafts are excellent, but if they have been subjected to abuse in their previous life, that may be impossible to detect visually. Personally, I cannot recall any failing.

The problem with such a component is that we can so easily overlook certain elements of the tasks that they are expected to do.

The surface upon which the oil seal lip runs needs lubrication, not only upon assembly. The surface needs to be of a certain roughness, not polished, for oil retention to ensure that the oil seal lip doesn’t wear out. The actual requirement for the surface finish will be as stated within any good seal manufacturer’s technical data if anybody would care to research it. However, if the surface is roughened up by common or garden green Scotchbrite, that should suffice.

I hope this information helps anybody unaware of the requirements for an oil seal to perform it’s function

Mark, I applaud your lathe work on the hub lining. I suspect all my hubs could do with that.

That said, I can’t quite get my head around what you have done regards the oil leak. In effect, you are putting it back together without having tried anything to rectify the leak. Is that right?

How badly are the brake pads impregnated with oil?

Paul

coaster wrote:Has anyone tried gently presurising the chain case and checking for leaks with soapy water? obviously would need to blow in via a bung in the breather and maintain a positive air pressure as it will escape via the kickstart and other orifices....or as suggested, new oil seal, o ring and a smear of silicone around the bearing before fitting.

As Paul said, oil on the shoes is a common issue, Im just wondering if anyone has ever worn their rear shoes out

That brake cam looks like an Li type whereas your should be the GP variety, not realy an issue so long as the shoes match.

Check Steve Richards on Youtube (The Steel Weazel) he talking about the front but its all relevent to thye reav Part one deals with taking a file to the cam
https://www.youtube.com/watch?v=JboLYuGHC10

I'll check the cam when I pop over to Cam Lam tomorrow, but I think it's correct looking at Stickies book - will watch the vid too - Thx

Warkton Tornado No.1 wrote:I am on record as stating that IMO the OEM layshafts are excellent, but if they have been subjected to abuse in their previous life, that may be impossible to detect visually. Personally, I cannot recall any failing.

The problem with such a component is that we can so easily overlook certain elements of the tasks that they are expected to do.

The surface upon which the oil seal lip runs needs lubrication, not only upon assembly. The surface needs to be of a certain roughness, not polished, for oil retention to ensure that the oil seal lip doesn’t wear out. The actual requirement for the surface finish will be as stated within any good seal manufacturer’s technical data if anybody would care to research it. However, if the surface is roughened up by common or garden green Scotchbrite, that should suffice.

I hope this information helps anybody unaware of the requirements for an oil seal to perform it’s function

I agree that the oil needs something to cling to - so far I've not removed the seal, so if it's sealing I'll leave it be.

Red & Green 3M Scotchbrite in plentiful supply here..

Storkfoot wrote:Mark, I applaud your lathe work on the hub lining. I suspect all my hubs could do with that.

That said, I can’t quite get my head around what you have done regards the oil leak. In effect, you are putting it back together without having tried anything to rectify the leak. Is that right?

How badly are the brake pads impregnated with oil?

Paul

Thx Paul - if you get your hubs to me I'll happily do the same to yours.

So I haven't done anything as after a good de-grease and run up there is no sign of any leakage. I left it alone save a clean and new nylocs on the bearing plate. The oil must have come from somewhere and quite possibly it'll show after a good ride, but until I see it come through I'll hold fire.

Shoes were just a bit oily in general & Cam Lam said they were asbestos so they've gone in the bin now.

It all looks very good as you'd expect from a scooter with a few hundred miles on it really.

Will report back after a road test..

I once turned my engine upside down on a bench to clean it and oil poured out from either the gear selector or clutch shaft and flowed straight into the rear hub contaminating the brake shoes . A classic example of a quick job turning into a bigger one !

Thanks for the offer to machine my hubs, Mark. It’s a pity you aren’t a bit nearer

Good luck.

Storkfoot wrote:Thanks for the offer to machine my hubs, Mark. It’s a pity you aren’t a bit nearer

Good luck.

Offer stands if you're passing. Only takes 5 mins to do.

Covboy wrote:I once turned my engine upside down on a bench to clean it and oil poured out from either the gear selector or clutch shaft and flowed straight into the rear hub contaminating the brake shoes . A classic example of a quick job turning into a bigger one !

I think we've all tried a short cut that turned out to be the very opposite!

..I could always put molasses in the gearbox!

LambrettaMarky wrote:

Storkfoot wrote:Mark, I applaud your lathe work on the hub lining. I suspect all my hubs could do with that.

That said, I can’t quite get my head around what you have done regards the oil leak. In effect, you are putting it back together without having tried anything to rectify the leak. Is that right?

How badly are the brake pads impregnated with oil?

Paul

Thx Paul - if you get your hubs to me I'll happily do the same to yours.

So I haven't done anything as after a good de-grease and run up there is no sign of any leakage. I left it alone save a clean and new nylocs on the bearing plate. The oil must have come from somewhere and quite possibly it'll show after a good ride, but until I see it come through I'll hold fire.

Shoes were just a bit oily in general & Cam Lam said they were asbestos so they've gone in the bin now.

It all looks very good as you'd expect from a scooter with a few hundred miles on it really.

Will report back after a road test..

I once got a mate to machine my rear hub as it was very scored. The result was amazing, the best lambretta rear brake I've ever used by a country mile.

I guess the rough surface finish was the cause of the improvement. I've since ridden it after 3 or 4 more owners and about 10 years later and while it's still very good, it certainly isn't as good as it was for the first year or so after I built it.

dickie wrote:

LambrettaMarky wrote:

Storkfoot wrote:Mark, I applaud your lathe work on the hub lining. I suspect all my hubs could do with that.

That said, I can’t quite get my head around what you have done regards the oil leak. In effect, you are putting it back together without having tried anything to rectify the leak. Is that right?

How badly are the brake pads impregnated with oil?

Paul

Thx Paul - if you get your hubs to me I'll happily do the same to yours.

So I haven't done anything as after a good de-grease and run up there is no sign of any leakage. I left it alone save a clean and new nylocs on the bearing plate. The oil must have come from somewhere and quite possibly it'll show after a good ride, but until I see it come through I'll hold fire.

Shoes were just a bit oily in general & Cam Lam said they were asbestos so they've gone in the bin now.

It all looks very good as you'd expect from a scooter with a few hundred miles on it really.

Will report back after a road test..

I once got a mate to machine my rear hub as it was very scored. The result was amazing, the best lambretta rear brake I've ever used by a country mile.

I guess the rough surface finish was the cause of the improvement. I've since ridden it after 3 or 4 more owners and about 10 years later and while it's still very good, it certainly isn't as good as it was for the first year or so after I built it.

Being eccentric is probably the main reason, but for sure bad scoring also not good. There is also a big improvement to be had by machining the shoes' contact area as actuated by the cam.