Scooterotica

It all goes a bit quiet during October and November of that year, I was busy with work and the weather was bad.

In the Xmas break I get out into the shed and drop the front wheel out.

This is also suffering fairly badly from the passage of time, and at least one winter in the old shed which had been leaking and damp which is when I'm sure most of this damage occurred.

I start to strip it down, the corrosion on it is every bit as bad as the rest.



This doesn't look to bad but if you got your nail under an edge the whole thing was lifting off in a single piece and usual white powdery stuff was everywhere.





The speedo drive gear is bust as well.

Yet another box of rusty parts added to the collection.



Just noticed this was being done on the on the dining room table the missis must have been out

I make up my mind that when the casings turn up from cleaning I'll get this blasted and coated again. My plan was to do the front hub, rear hub and side casing as per the original but decide to change the colour for a gunmetal metallic.

I should say at this point that my brother-in-law was doing the blasting on the engine casing as a favour and this was taking a little longer than I'd planned for but you can't push somebody who's doing you a favour too hard.

It all goes a bit quiet for a while again.

DaveTomo wrote:enjoying this

Cheers, Dave.

A lot of people have helped me out with my projects, with either parts or advice when needed.

I've had Lambretta's consistently since the mid 80's. I'm a reasonably competent mechanic, which I owe to my old man who was a proper engineer and who spent some of his final years tinkering with mine and my brother's various projects and keeping them on the road.

The strip down bit is a bit routine, but I made a number of mistakes and bad decisions as this went on and I'm going to expose some of those as we go on, they've cost me time and money. Maybe while I'm still learning, and there's always something to learn with these things, I can return some of the favours

Fast forward to March 2012 >>

I'm in Vienna working



The engine casings turn up clean!





I'd placed a bolt in NEARLY every exposed thread as I have had stuff blasted before and with coarse grits this can lead to thread damage. In this case, even though you could see media residue and it was very fine, I'd omitted to put blanking plugs in the oil breather, filler and drain plugs and these were very rough to put new plugs into on the first pass. I'm convinced this is related to the blasting process.

Due to the presence of blasting media still on the casings I washed these very carefully with clean petrol then took them to the local pressure wash and blew them over with that too. There's too many tales of kits and cranks being wrecked due to the presence of grit or blasting media not to be careful about this.

So now this is back, I take the side casing and hubs to a local dealer for coating, promised a two week turn around and a proper job.

I wait two weeks, no call to say it's ready. I call, there then follows a running saga of excuses and apologies, until it gets to the point where I'm starting to think he's either lost the stuff or sold it by mistake. Eventually I try suggesting he tell me where it is and I'll go and get it myself.

Finally on the 19th June I get the call that the stuff is back. I go and get it and again get a whole load of apologies and excuses. It's all wrapped in bubble when I collect it, it's the day before I fly out on holiday and I don't really get a chance to inspect it closely.



Initially it looks quite good but close inspection reveals the hubs haven't been masked properly. The area where the speedo drive goes has been coated as have the pins for the disc itself, so no way that's going on. It takes several (more like a dozen) hours work with emery paper to sort this out. The front been coated over the studs for the wheel and the rear has been coated in the exposed thread. I had to get a special tap to get it out of the holes M10 x 1.00 left hand, in case anyone asks.

Rewind to March <<

While the above saga is unfolding I get on with the engine I have.

A second cheapo workbench comes my way, but not a patch on the skip workmate, anybody do replacement tops for those?

Mag housing filled first





Fitting the bearings and seals is easy enough, if you heat it adequately the bearing should drop in. You can buy special tools as drifts for the seals but properly sized sockets and extensions are just as good.

One lesson from this is to do this indoors and buy decent circlip pliers. It took about half a dozen goes to get this in and trying to find it in the flower beds is not fun!

Next the rear hub bearing goes in



and a new race for the gear cluster bearing



then the retaining plate for the rear hub bearing.



I'd used stainless studs here for the retaining plate and for some reason on the last one as I'm torquing it up it shears. So I strip the rest off and there's enough to get the mole grips on and get it out. Lucky it went at the bottom of the top thread and not next to the casing. I can only conclude here that the stainless studs are less tolerant of over torquing compared to normal ones or more brittle as the torque on these isn't high. I'm very careful now with stainless studs and generally will avoid them for things that need to be real tight. There's also the usual concerns over stainless in alloy so if I do use them I use coppa-slip on the part going in the casing.

The drive side bearing goes in next, it's a half shielded bearing, I've removed the seal from one side already. I've also already added these cutouts which allow you to remove the bearing without hitting the inner race, they're a little scruffy on this case but functional as first time I did this I put the bearing in the wrong way round with the seal facing the chain case and had to knock it out again, doh!



The layshaft goes back in next with a new sliding dog and pawls on the wishbone. You can knock this in gently but there's no substitute for pulling it in and torquing it properly. At this time I don't have a hub as it's at the powder coater, nor do I have a spacer tool.

I push on.

The drive seal plate goes on. I rate the hex screws, as long as you have a quality hex key these should give you no problems.



The crank goes in.



At this point I should maybe say where I thought I was going with this motor. My plan was to build a cast iron barrelled 225 using my original barrel with a rebore, I hadn't thought about anything else at that stage and wasn't planning on spending a fortune on this rebuild. The crank choice was a fairly standard PM Xtech race crank with 107/58 stroke, which I already had on the shelf.

The mag housing goes on



The front sprocket goes on. This is a 19 tooth, I'd accidentally ordered a 46 tooth MBD rear sprocket over the winter and didn't think they'd change it after 4 months so opted to try 19/46 with the GP box for 4.84 ratio.



I'd also got a Jockey's rear brake kit, this is very easy to fit and I'm hoping will improve the very poor original rear brake.



The stator goes in. Note another job I'd done over the winter was to convert the original AF Ducati electonic stator to give me the option to run it with the Wassel type conversion (extra yellow wire on the bottom coil)



I'd also converted the orginal GP gear arm shifter to have a stud rather than the fiddly circlip arrangement



This gets us to mid April and a change of thinking on the top end.

Great stuff.

The tops of my cheap aldi workmate just screws on. They are only shitty mdf and if you're welting anything on them they will just crumble.
As the ex has the proper one I can't check, but suspect they are similar fixings.
Any chunk of 3/4" ply should do, you can drill holes where it suits - or not.
I just screwed an extra batten underneath.

Enjoying this and looking forward to the next episode.

I couldn't find anyone local who was prepared to rebore my old barrel, I'd bought one of Ron's Avanti pistons with a view to this rebore. I then saw a barrel on ebay and paid too much for it as is often the case when you've decided it's the thing you need. You always forget that you need to add the postage into the overall cost.

When it turned up the seller hadn't mentioned that it had been been rebored to 71mm and topped and tailed and the Avanti piston fell straight through it, so that went back on eBay with a more full description and a £30 loss.

I start fishing around for other ideas. I don't have £500 quid to hand to spend on a RB / TS1 / Avanti etc. all of which are on my wish list. I have a good quality 70mm piston already so I'm looking for a barrel to match. The Rapido comes as a barrel only option for less than £200, add a head, say another £40 and it looks reasonable. I speak to Ben at AF and he suggests I send the piston down so they can match it to a suitable barrel for tolerance. This I do and a week later it turns up with a new AF head as well.

Tolerance and ring gap are good and I dry fit it to check the timings.





These don't look so good

The piston is 1mm below the top of the barrel at TDC with no base gasket fitted.

176 - Exhaust
136 - transfer
139 - inlet
20 - BD



It's also apparent that the gasket face on this casing is quite high compared to some others.

Having a play with the calculators fitting a 60mm crank improves the situation a little. Darrell Taylor has a balanced 60mm crank for sale and in discussion with him I decide to send him the barrel, piston and head to see if he can improve this at all.

I go off on holiday while he has this. I get the whole package back when I get back mid - July.

excellent read thank you for posting rosscia
When you get a mo could you please explain how you measure the port timings please

Next I did the gearbox. I'd decided that the GP style endplate wasn't really the best set up so went rumaging in the shed for an Li style endplate. I find a couple both a little ravaged but clean up with judicious application of the old wire brush and grinder.

Before on the right after on the left



New bearing and track fitted and bolted in with the MB high tensile bolts and two dowels.



With this bolted down the the gearbox locks solid. I think this is because there's no hub and it's not torqued. This brings me to another little learning experience.

When I fitted the layshaft, I'd used a spacer and try to tighten the nut up, the gearbox turns. You can't hold it and I'm very reluctant to start jamming stuff in the gearbox to lock it given that I'm going to tighten this hard. In the end I work out that the only way to do this is to reassemble the gearbox, put on the plate, fit the clutch centre spider and use a clutch holding tool to lock the whole thing up till I tighten the hub nut on the spacer! I have to then disassemble the whole thing till I figure out why it's locking.

It's still tight but at least I can turn it with the layshaft torqued. I take some measurements with feeler and figure that the shim needs to be thinner, different combination of gearbox, layshaft and endplate I guess. I order a few shims and on the next pass get it right.

New engine mounts go in



I've already stripped out the PM crank and now fit the Evolution one.



As you may have seen in the 'today's cockup' thread in my haste to fit this I neglected to fit the inner race onto the crank. I carried on, put on the mag flange, the stator and the flywheel before I noticed the the flywheel had quite a bit of up and down movement...diddy...

The whole lot comes back out and I fit the race and reassemble it all.

Now I have another issue. As I torque down the flywheel nut the the flywheel starts to catch on the pickup and stator. At 45lbft it's fine but as it comes on to 50lbft it starts to catch and at 55lbft it's rubbing quite a bit. This was never an issue previously and i can only put it down to the rebuild. As a first step I order some thinner mag gaskets hoping that an extra 0.5mm might be enough to clear it, but it isn't.

Next I try on an AFR flywheel this is fine when torqued down, oh the irony

I take it off and get the vernier out, it turns out the AFR is 1mm deeper to the inside face of the flywheel than the Ducati one. I'm not a fan of machining the mag housing to get clearance as I think this can lead to alignment issues on the pickup, so it looks like it'll need to be the flywheel.

Next time I'm in Glasgow I take this in to West of Scotland Engineering and they shave 1mm out of it, same day, for a very reasonable £15.



With this refitted, torqued and more importantly, clearing I set up the timing marks using a dial gauge.



I've set it 18 static, which is 1.8mm BTDC. I will strobe it to make sure later.

johnny LIS150 wrote:excellent read thank you for posting rosscia
When you get a mo could you please explain how you measure the port timings please

I have to admit this stuff was new to me too at this point, tuning when I was a lad involved making the holes as big as you dared and fitting the biggest Amal you could find and the expansion of your choice fresco / mikeck / dj ( or budget more like ), not very scientific.

There's a couple of ways to measure port timings. You can use a degree wheel bolted to the flywheel and a fixed pointer looking to see when the piston clears the edge of the port. Some can do this accurately but I think you need a rather big wheel to be accurate.

Most people, however can work a vernier gauge and there's several different online calculators that will work it out for you given some known parameters.

Usually you need to know -

The stroke
Conrod Length
The distance that the edge of the crown of the piston is from the top face of the barrel at TDC - usually referred to as 'deck height'. This is positive if the piston is below the gasket face and negative if above or 'out the top'
The distance from the top of the barrel to the top of the exhaust port
The distance from the top of the barrel to the top of the transfer ports - this ideally should be the same for each, but often isn't and should be evened out if possible.
The distance from the top of the barrel to the floor of the inlet port
The piston height

I've measured these on the barrel and written them on the port map above.

After that it's geometry and maths - which are not strong points of mine and probably why much smarter people have created the online tools.

The only formula I can remember related to this is -

Blowdown = (Exhaust Duration - Transfer Duration) /2

It seems that this is a key piece in the jigsaw and somewhere around 25 - 29 seems to be desirable.

There used to be a link on the home page but I don't see it now. One of the best I find is Eden's on his Lambretta Images web page.