Some parts of a Lambretta are just plain old – weak! Not as weak as a Vespa and I’m only guessing when both manufacturers started they were trying to save money by making castings as thin as they could to save metal and money.
The Series one wasn’t new at the time, it followed all the older upright cylinder models, by the time the Series 1 came you would have thought they improved the casings – but no! Bodywork wise, some of it was over kill and thick and other parts were so thin they cracked straight away!
The horn casting is particularly weak, there is hardly any metal for the headlight screws which always pull out. Innocenti never heard of grease or anti seize compound and they used steel screws which just seized into the alloy! For the sake of a fine smear, screws would still be coming loose 70 years later.
It’s rare you find a Series 1 horncast that hasn’t had stripped threads, or screws broken in the casings or cracks or parts just broken off!
When this happens some heavy fisted person usually tries to drill out the broken screw and then slips to one side creating a hole in the alloy where a professional can not drill out the screw and cure the problem. Usually theres a gap and the only thing a professional can do is grind out the alloy, reweld, fettle, drill and tap the best you can back to standard.
Now if they left it alone, a professional can drill and tap out a broken screw which takes no time at all. Even if the alloy has corroded around the threads it’s no issue to drill bigger, tap out and fit any of the various inserts available.
Here we have a horn casting that’s had the lot – parts broken off – threads gone – threads drill off set and cracks!
This one had the lower part of the horncast missing. You can build it up with weld then grind it all to shape – or like this one you can make the part that is missing in the milling machine and weld it in place. As you can see from the photos, theres lots been done to this one.
I can repair engine lugs, crankcase threads and much more in the time it takes to repair a bad horn casting – I can even tune two cylinders in this time!
Horn castings are nearly impossible to hold straight in a vice, you certainly can’t hold them in a milling machine – its down to holding them with one hand and using the other to do the intricate work.
This one took nearly five hours! Now you could find another which is better but the chances are it needs as much doing to it.
Today S1 horn castings are becoming a rare thing. This one is heading to Canada.
Any questions ask mark@mbscooters.co.uk
