Rear hub bearing

First thing was to get the rear hub bearing fitted. I did this by hammering it in, using the old bearing as a drift. There's a lesson to be learned here - never throw any of your old bits away until you've finished. Here's the old bearing on top of the new, after installation:



When fitted, the bearing won't sit flush with the casing - it will be slightly raised.

Fit the oil seal, with the circular spring facing into the bearing. Oil seals like this should always have the side with the spring facing the source of the pressure.



Then fit the washer and flange to keep it all in place. I used nylock stainless nuts and washers but for some reason never took a photo:

Engine mounts

Probably one of the most difficult jobs on a Lambretta in my experience is removing and replacing the engine mounts. My technique was to use a vice, some heat, and to use the new mounts to drift out the old ones while fitting them. The only drawback is that it's difficult not to mark your new mounts with the jaws of the vice. My grandfather was a skilled metalworker for BSA, first making guns and then motorcycles, and he used to cover the jaws of his vice with lead when securing objects he didn't want to damage. This is probably a good tip if you're into pretty chrome bits on your scoot and you don't want to mark them.



In the above photo you can see the new mount being pushed into the casing, and two sockets being used as props to allow room for the old mount to be pushed out the other side. The flame of the blowtorch doesn't show up on the photo, but it is there. When heating the casing you don't need to move the flame around at all; just keep it focused in one place and the metal will do the dispersal for you, and very efficiently.

I had to put an extender bar on my vice handle and virtually hang my whole weight off it to get this to work, all the time worrying that I might be about to crack the casing or break the vice. In the end it went without a hitch.

If you have holes in the rubber part of your engine mounts, make sure they are positioned to the front of the bike. The mounts I used are the ones recommended by MB, part number MBL0162.

Parts!

Here's some of the parts I've bought for the engine rebuild.



You can see a gasket set, oil seal set, large engine mounts, long engine mount bar, clutch discs and plates, chain guides, shims, o-rings, nuts and bolts and the rear bearing. For a lot of these parts I would normally nip round the corner to my local scooter shop Fanatic Scooters but I chose to rebuild my engine in the month of the year that they close! So I used MB Developments (or www.lambrettaspares.com) and Scooter Restorations. MB's delivery is speedy and efficient, but Scooter Restorations closed over the Christmas period and then they were let down by FedEx's glacial service, so my stuff took 18 days to arrive. On the plus side they did give me a nice free mug, and my orders since have been very quick.

For the end plate gear cluster bearing (6004 SKF), the drive-side bearing (6305 SKF) and the flywheel-side crankshaft bearing (NU205 ECP SKF Roller Bearing) I went to bearingboys.co.uk, where I saved myself a good few quid instead of using the lambretta specialists. There are lots of direct bearing suppliers on the web so it's worth shopping around.

Cleaning parts and casing

Now its all virtually stripped down its time to take stock and clean. I removed old gaskets from the casing using a screwdriver and sometimes a chisel, taking care not to damage the surface. Then I used a wire brush attachment on a drill to clean the outer casing.



Then I cleaned the whole lot, inside and out with an engine degreasant called 'Gunk', and then washed it all off with warm soapy water.

Some of the parts that were due to be refitted I gunked, washed with warm soapy water, and then ran them through the Zanussi parts washer that we happen to have in our kitchen:

Tip: don't do this. Your parts will end up nice and clean, your dishwasher won't. I spent longer cleaning the dishwasher than I would have cleaning the parts properly :)

Gearbox disassembly

Undo the six bolts holding down the end plate, and then lever it up with a large screwdriver or similar. You may need two. Or three. And some patience - mine seemed to be sticking a bit. When it's off , this is what you'll see:



At this point it's worth noting what you see so there's no confusion when you're putting it all back. Note the large gearbox shim sitting next to first gear:



And the layshaft needle bearing and shim at the end of the layshaft:



The gears just lift out. Again, make a note of which way round they go. I tied mine together with a cable tie after removal so I didn't have to work it out again later.





The everything lifts out with ease now. Be careful sliding off the sliding dog as there are two ball bearings and a spring controlling its movement. The balls have a tendency to ping out at great speed, so cover the assembly with a rag to catch them.

One thing that is difficult to remove and is often left in situ is the 'bearing track' and shim behind it, which hold the cluster and the cluster bearing in place.



The layshaft can simply be knocked out now:



And the bearing can be knocked out the other way with a bar and socket (assuming you've removed the hub plate and shim etc.)





My bearing felt particularly stiff when turning it by hand - it remains to be seen how this compares to a new one, but I do wonder if it was suffering from wear or damage of some sort.

Crankshaft removal

The Lambretta crankshaft is a pretty neat design. Once you're down to your drive sleeve you can put a bar down the middle of it and tap the end of the crankshaft through the bearing. Once through, you need to nurture the whole crankshaft assembly out complete with conrod at just the right angle. Simple as that.







For some reason, I don't have a photo of the crankshaft - believe me, it's out :)

Drive bolt, cap, spring, dog, sprocket, sleeve...

...you know, that bit at the end of the crankshaft that drives the chain.

You should really tackle this before removing the crownwheel at the other end of the chain as you can use this and the chain to hold things in place when you're undoing the bolt. I had already removed mine but placed it back temporarily. The bolt holding the drive cap/spring/dog/sprocket/sleeve is a normal-threaded bolt. I say this because I wasn't so sure, and when you're trying to undo the thing the spring compresses and you get this uneasy feeling that you're doing something wrong.

Anyway, heres the whole lot gone except the drive sleeve:

Clutch removal

Here's my cheap Indian clutch removal tool installed and in action, compressing the flange down onto the five springs.



This releases the compression on the circlip, allowing it to be removed from its position and freeing up the clutch plates. When the circlip is removed you can unscrew and remove the clutch removal tool and simply lift off the clutch plates, steel plates, flange and springs.

To continue you need to remove the 22mm nut that holds down the clutch spider and crownwheel. It is secured with a tab washer which first needs to be released. To remove the nut you need to prevent the assembly from rotating with your spanner/socket, and the best way to do this is using a clutch holder tool:



When done you can simply lift off the spider. Note that the shaft has a bearing bush on it which is easy to miss - it's just a well-fitted metal sleeve that aids rotation between the spider and crownwheel. You can now tease off the chain and lift off the large crownwheel. Finally, you should find one or more shims beneath the crownwheel on top of the end plate bearing.

This picture shows the gearbox end plate with the layshaft poking through the end plate bearing. On the bearing you can see what are two shims:

Chaincase removal

To remove the chaincase simply undo all the nuts around its circumference and then try pulling it off. If it's pretty stuck you can use the kickstart for leverage, or you can very carefully prise it off with a screwdriver but take care not to damage the casing.

When mine was removed I could clearly see evidence of what looks like a botched clutch replacement. This image shows damage to the kick mechanism and return spring where the clutch assembly has rotated against them:



And this one shows similar wear on the inside of the casing where the gear selector is housed. It is clear the clutch assembly has rotated against it:



Perhaps this only happened for a few kicks after a botch clutch job and then the mechanic dismantled it and started again. I can't believe it would have run particularly well if at all with this kind of contact, and changing gear would presumably have been very difficult. Or perhaps the clutch circlip gave way one day in Bangalore?

Anyway, here's the scene in full with the chaincase removed:



Next step is dismantling the clutch...

Cylinder head, cylinder, piston

Head and cylinder removal is very straightforward. Four nuts on the head hold it and the cylinder against the block with long rods threaded at each end, passing through the cylinder casing. When you've removed the head and cylinder, the rods can be removed by threading two nuts on the upper thread, and then turning using the innermost nut.

To release the piston from the conrod, simply remove the two circlips holding in the gudgeon pin, then push the gudgeon pin out from one side using a suitable bar or socket. Below you can see the gudgeon pin, circlips, bearing, piston and the conrod hanging loosely from the crank:



It looks like my piston has had a hard life, with lots of deposits on the top, and what look like scores or pitting on the wall:

Mag housing

This is the view from the back of the mag housing, showing the crankshaft bearing. Beneath the oily mess you can see the oil seal and huge circlip holding it all in. I had trouble removing this circlip as my circlip pliers weren't up to the job. I had to resort to standard long-nose pliers and a screwdriver. So much for 'the right tools'!





To remove the bearing I used a suitable-sized socket and a mallet to hammer it all out.

Flywheel removal

Here's a tool you can't do without, a flywheel puller. I got it from MB Developments and it's top quality.



It threads into the flywheel, and then a bolt is wound through the centre to push it out from the end of the crankshaft. There are a few methods of holding the flywheel in place while you do this. Whatever you do don't wedge something between the cooling fins, as they will break off!



I chose to insert a bar into the cylinder through the inlet port to stop the piston moving and therefore the crank turning. With hindsight I should have used a plastic or wooden object as there is a risk here of marking the cylinder or port.

When the flywheel is off you'll see the stator plate. This is held on with three set screws and is easily removed along with the wiring. Then you can remove the mag housing by undoing the three bolts and knocking it away with a wooden mallet.



Behind the mag housing you'll see the crankshaft in all its glory:

Organisation

As I'm stripping the engine down I'm careful to ensure that I know what it all is. I purchased a load of Supagrip bags from ebay and every nut, bolt and washer is bagged up and labelled by name with a marker pen. If I'm at a loss for a name then I might even put the reference number from the parts diagram:

Rear hub removal

First off you need to remove the screw that holds the locking washer in place. This came out surprisingly easy on mine. You can then prise off the washer....

...to allow us to undo the main hub nut.

This bit would probably have been easier had I loosened it before removing the engine from the bike, as there would have been natural resistance against the spanner. I'll remember this next time. The hub nut, unlike the flywheel, is a normal thread. The nut is bigger than 24mm (the biggest socket in my set) so I had to use my trusty adjustable spanner. I rested the end of the spanner on the vice, and gently tapped the hub round with a mallet and some wood.  

Once the main nut is removed you can insert your hub puller into the three threaded holes in the hub.

I was let down here by a cheap tool - my hub puller failed on me. It was a simple design poorly executed, comprising a steel disc with a nut 'welded' to the centre to allow a bolt to be threaded through. The problem was the weld was more of a braze, and the join gave way when put under tension, resulting in the nut coming away from the disc. The lesson here is don't buy cheap rubbish from ebay, and when you buy a puller go for a well designed one.

So, I resorted to the more traditional method - the mallet. The risk here is that you might damage something. Mine came away undamaged with the second strike, revealing even more how poor my tool was as the hub obviously wasn't siezed on.