Vespa PX LML Stella - Drilled Air Cleaner modification

 The reason I'm writing this one up, is because I had heard about this modification, but it took me a while to find out how to do it.  So borrowing from the tribal knowledge of many who came before me, here it is.

There is a space above the jets on the Spaco / Dell'Orto carb which is covered by the air cleaner.  This casting has a recess in it that is positioned directly over the top of the jets.  By allowing direct flow to the jets with the provided holes, the difference is amazing.  I don't have a dynamometer, but my "standard test hill" is the proof.  I increased one main jet size and was able to take on the test hill with cooler temperatures and 5mph faster than before.  This is the easiest and most beneficial modification to the 2T engine.

With credit to VespaLabs, here's the difference in the original and drilled air cleaner.

This modification altered the jetting :

DR177 and SITO+ Stock 20/20 carb 48/160 idle, 160 air, BE3 atomizer and a 107 main jet. Drilled stock air filter frame stripped and replaced with UNI foam.

Mix Turns = 2.0

Project Vespa Smallframe - Points and Condenser

 Everything was running so well, until the spark became intermittent.  So the points and condenser were the first target of scrutiny.  I never confirmed the ignition timing, the bike started and ran well enough, so I didn't question it.  It turns out it was just set to the nominal marks on the stator, which is not horrible, but just not ideal.  

After a readjustment to the specified 17 degrees BTDC confirmed by a timing light, I set off again.  It wasn't much better.  At that point I ordered a set of points and a condenser.  Immediately upon removing the condenser from the packaging, I tested its value as 225nF (which strangely was the same as the one I took out).

I will keep the original as an emergency spare.  It looks like it was recently replaced anyway.  The erratic nature of the mis-fire led me to believe it was point and condenser related, but I had to rule that out.

After setting the timing up with the strobe light, it does fire nicely at 17 degrees right at idle.  However its still somewhat erratic at higher revs.  I finally removed the ground connection on the stator and re-soldered the joint.  At the same time I ditched the stock condenser and used a 630v rated vacuum tube radio capacitor.  At 330nF it should be close enough.  I also like how well it mounts.

Now that I have the ability to strip the flywheel and re-mount it with my eyes shut, the work went swiftly.  The engine started on the first kick and revs as it should.