Cylinder kit

I bought a cylinder kit from Sundar Scoots this week. They seem like nice people, and the package arrived today in good time and very well packed up.

Michael at Sundar tells me the head is made by SIL and the rest of it is made elsewhere. The finish of the cylinder and piston looks excellent and exceeded my expectations. Here's a couple of pics:

Unfortunately the head is a completely different story, and its finish is pretty ropey to say the least. I'm not sure if my expectations are a little high and they're all like this, or whether I've been sent a duff one. I'm sending these pics to Sundar to see what they think. Look at the bent fin with the hole in it in this shot:

And in this shot (click to zoom in) you can see the rough finish generally.

The thread of the plug socket looks a little suspect too, but I'm not going to try a plug in it until I've heard from Sundar. If they're all like this then so be it, but surely not?

UPDATE: Sundar are sending me a new head, they were very apologetic about the quality of this one. Excellent service! I'll post up some pics when I get a chance.

Installing the crankshaft

When preparing to install the crankshaft I realised that the inner race of the flywheel-side bearing was still on the shaft. This is a real pain to remove! You can see it here on the left:



I removed it very carefully using an angle grinder. The one tip I can give, other than make sure you have a very steady hand, is that it's very difficult to tell when you've gone through the ring and are grinding the shaft - you have to look very carefully for a hairline as the two parts are so tightly fitted. Hopefully you won't actually go this far, but if you do it's no disaster as long as you haven't damaged the oil seal faces either side of the ring. When you think you're nearing the shaft, give it a knock with a mallet (on the side of the shaft, supporting the other side) regularly and you'll see movement before you've cut completely through. Here's my shaft finally with ring removed:



Freeze the crankshaft overnight before installing. When inserting into the drive-side bearing do not under any circumstances knock the crank in with a hammer or mallet. Instead use a crankshaft pulling tool or use the cush-drive bolt to pull the crankshaft through. I did this along with a 21mm spark plug socket that worked a treat:

Installing the drive side bearing

The drive side bearing is a tight fit, so stick it in the freezer overnight before fitting it, this will shrink it a little to help things along. Heat the casing, and then insert the bearing - it goes in either way. I used the old bearing as a drift, with a block of wood to spread the blow to the outer race. You must make sure its all the way in, but at the same time be careful to stop bashing it when its gone as far it can, as you may break the casing. When it is you shouldn't be able to slot in a feeler gauge between the casing and the outer race from the other side.

The oil seal fits into the drive plate with the sprung lip pointing towards the crank. All oil seals like this have the spring on the side of the source of oil or the highest pressure. Make sure the seal sits as flush as possible with the face of the plate.

Grease the bearing with high melting point grease, and then place the gasket centrally onto the bearing.



Make sure this sits snug, as if it is raised up anywhere it will cause problems when screwing down the plate. Now place the plate in place - it should sit virtually flush without screwing it down. If it doesn't you may not have pushed your bearing all the way home. This happened to me, and I was only to find out a lot later after fitting the crankshaft and mag housing, and finding that I'd run out of room and my crank web rubbed on the mag housing!



Use threadlock when fitting the plate screws, but do a dry-run first without threadlock to ensure the screws go in all the way and that there are no blockages or problems. When finally fitting, tighten each screw a little at a time in a diagonal pattern, to ensure that the plate goes down flat. Screw in to about 0.5 kgm (this isn't easy with a flat screw head, and I think next time I'll use allen-head screws), and check again that the plate is flush with the casing.

Gearbox rebuild

Be sure to replace the o-ring on the layshaft. You'd be stupid not to at this point. This photo shows the old one having been cut off and the new one fitted. You can just about see how square and flat the profile of the old one had become.



Tap the layshaft into the rear bearing - you'll feel the resistance when the o-ring goes through. Keep going until the splines meet the bearing as seen here:



Fitting the sliding dog is awkward. Two of its six arms have chamfers on the bottom side, allowing you to slide it down the layshaft while pushing two ball bearings against the end of the spring which goes through the shaft. If you let go of the balls too early they'll fall away from the layshaft and you risk bending your spring if you continue to push the sliding dog down. Basically you need to hold on to the balls as long as you possibly can while sliding the dog down, and then when you must let go hopefully the chamfers should push the balls against the spring into the layshaft. Just persevere, you'll get there.

Prior to fitting the gear selector wishbone, I replaced the selector pins or 'pawls' as MB call them. This photo shows how much the old ones (shown still fitted) had worn:



After the selector is in, install the gear cluster bearing then the gear cluster, not forgetting the shim in between. Then install all the gears onto the layshaft and at the top place the small shim and the needle bearing - both of these I bought new.

Now for the large gear shim - this separates the gearbox end plate from first gear and is available in a multitude of sizes. MB Developments go from 1.8mm to 2.8mm, and Fanatic sell 4.4mm ones! To work out which size shim you need, fit the gearbox end plate and the rear hub (or at least the hub nut with a spacer tube to replicate the fitting of the hub), and with a feeler gauge measure the space between the end plate and first gear. The ideal distance is somewhere between 0.07 and 0.3mm. I have to say I'm not convinced fully tightening the rear hub is necessary; as long as the splines on the layshaft are fitted right up against the bearing then there's not much here to compress when tightening the hub nut - no gaskets or seals etc. Don't take my word for it though.

My old shim was ridged and worn, so it was near impossible to take a correct reading. You can see the wear here:



This caused play of considerably more than 0.6mm. I couldn't measure exactly how much because you have to bend your gauge to reach the right bit, and bending anything more than 0.6mm into this space is a little tricky. My existing shim was a 2.26mm, but the worn groove on both sides looked like I'd lost at least 0.5mm of this. With hindsight I shouldn't have even bothered measuring it with this shim as it clearly needed replacing. I bought some replacements from MB advertised as 2.0, 2.2 and 2.4mm, but actually measuring 1.96, 2.27 and 2.44mm:

Before fitting the end plate a new gear cluster bearing (6004 SKF) was installed using the old one as a drift. Here's a photo of it prior to the large circlip being installed:

And I can't carry on without showing you a pic of the gearbox before putting the lid on:

For some reason I really hate nuts and studs, so to secure the endplate I used spring washers (from Screwfix) and bought some hex set screws (which your everyday man on the street would call a 'bolt') from MB, part number MBFH7X25SC to precise. Their website says "Amongst many applications this fastener can specifically be used to secure the gearbox endplate".



Unfortunately they're too long for my casing. The middle screw in this photo is wound in as far as it would go:



Perhaps the holes are shallower in an Indian casing, or mine was from a dodgy batch in the factory? Either way, where needed I cut the screws down to the right size with a hacksaw - none of them ended up being shorter than the standard studs that were fitted previously. Some of them I didn't need to cut, meaning that my holes are variable! Whenever you cut a bolt/screw always put a nut on first and cut below the nut. Then when you take the nut off it will remove any thread damage or burr that the saw created that might make inserting it difficult.

When fitting the end plate make sure it slides on squarely onto the gear cluster, and tighten each bolt a little at a time.

I ended up using the 2.44mm shim and measured a healthy clearance of under 0.27mm. Job done:

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 :)