Vespa Engine

The engine in the poor Vespa was completely siezed, rusty, and of course full of the ever present spiders.  After removing the engine and swing arm assembly from the scooter, I set up a table in the basement to work on it.  

One of the first challenges was simply de-griming the engine.  In hindsight, I should probably have used foaming engine degreaser and a hose.  Instead I scraped off what I could, and started liberal applications of penetrating oil to start freeing up some of the badly rusted bolts.  Most came out eventually, though there were a few that had to be removed by Pat at Scooterworks while the engine was up there.  Only the muffler mounting bolt snapped off, and I had to drill out and re-tap the hole for a new bolt.

The piston was seized in the cylinder, but the cylinder wall was still in good shape and even had a light coat of oil on it.  I was able to drive the piston out – should have used a chunk of dowel and a mallet, but instead I used a socket extension.  The top of the piston now has a hammered finish, but it’s still OK.  I found there was a lot of crud caked around the piston skirt.  Nothing was rusted or corroded to the point of being damaged.  Despite the relatively low miles (about 9600 on the odometer), I had already decided to install new rings and have the cylinder honed.  I had also counted on having to buy a new piston, but the original is still good – great news, and saves $50 for a new one.

I took the cylinder, head and flywheel to a local motorcycle shop and had them bead-blast the parts and hone the cylinder.  While that was going on I was able to split the two halves of the engine case, and was absolutely thrilled to see that the inside of the engine and gearbox was still clean and coated with oil!  The crank bearings were dry, black with soot and didn’t want to turn, but a shot of penetrating solvent oil freed them up immediately.  A little 30 weight and they were smooth and free, no sign of pitting or galling.  Fantastic news.  I went ahead and replaced the shift cruciform while I was in there, but all the gears and bearings were in perfect condition.  

The clutch was a mess.  I had to replace all of the cork faced friction plates and sand the smooth plates to remove the surface rust and disintegrating cork.  Both crank seals were hard as rock and in need of replacement, and of course all the gaskets needed to be replaced.  I also completely disassembled the carburetor and rebuilt it with new gaskets and seals.  New parts came from Sportique.

I removed the stator plate and discarded the old points and condenser.  The coils are in good shape, but some of the old cotton insulated wiring needed to be replaced.  I picked up some various colors of stranded wire to rebuild the stator plate wiring.  The external ignition coil measured OK with an Ohm meter, but the high-voltage lead was beyond saving.  Fortunately, I found that the coil could be disassembled by simply removing the bolt from the bottom – I just replaced the HT lead (the spark plug wire) and put it back together.  Wonderful news!  Another $37 saved by not needing a new coil.

Seal installation is simple, putting the halves back together without the special Piaggio crank pilot tools is very challenging.  I eventually took the case up to Scooterworks to have them clean it up and reassemble it.  I planned to pick it up and finish the engine rebuild myself, but had started to consider letting them do the whole thing and just pick up a running, tuned & timed engine. 

In December of ’05 I finally had the engine delivered here. UPS shipping wasn’t as horribly expensive as I thought for the engine & gas tank. Within a day I had the cylinder and head installed, and it turned nice and smooth.  Next came the stator plate and flywheel, plus new wiring for the external coil. Eventually I got it all in place and got a nice spark when I kicked it over by hand. With some help from the great tutorials and help files at, I was able to print off a degree wheel and set the timing and point gap.

I now have the engine completely together.  I installed a new spark plug and drilled out and tapped the muffler hold-down bolt hole, because the bolt snapped off when I tried to remove the muffler.  I have the carb temporarily bolted on and test-fit everything into the body to make sure there would be no surprises during reassembly.  I hung an oscilloscope on the two AC output leads, and I do get AC voltage on both of them so I should have lights and a horn.

On 12/17/05, my son and I shot a little starting fluid into the carb and pulled the kickstart lever a few times – which is tough to do; the little guy’s got some compression!  Anyway, on about the fourth pull it started and ran for a couple of seconds, which is all you could expect on a short squirt or ether.  It ran amazingly smooth & quiet, far more so than I expected.  Of course I was surprised it actually fired, but at least now I know I got it all back together right.  

On 1/22/06, we ran the engine at a friend’s auto repair shop.  We ran about a cup of oil & gas through it, with and without the muffler.  The engine runs strong and steady, and I was able to verify that I get AC from both coils that supply power to the lights and horn.  I need to tweak the timing for a degree or two more advance, and figure out what to do for an air filter – I can use the original, or rig up a K&N or something.  I’d like to get the engine running right and tuned (carb & electrical adjustments made) before reassembling the scooter.

2/12/06 – With the timing tweaked for about a degree or so more advance, this engine starts and runs on the first kick, every time.  Me, proud?  You bet!!