Fuel Level Sender repair - Vespa PX and LML Stella scooters

I've been asked a few times on how I managed to make my Genuine Scooter Stella 2T fuel level sender reliable.  So when the opportunity to fix the sender unit on my friend's scooter came up, we decided to take photos this time.

The principle of the sender is very basic, but some of the materials chosen when it was manufactured were not ideal.  The sender works with a float on the end of a stiff wire arm.  When the float moves around the fulcrum pin, a wiper contact slides across a variable resistor.

The first step is to pry open the tabs which retain the cover over the mechanism.  It is wise not to over-bend these, because they are small and fragile.

Once the cover is removed, the mechanism is exposed.

The float goes up and down which moves a wiper contact along a nickel-chrome wire wound around an insulating material.  This forms a variable resistor.  The problem is that this insulating material is not very stiff and over time it bows away from the wiper in the middle.  When the nickel chrome wire is no longer in contact with the wiper it causes the gauge to read EMPTY.  Rather than risk snapping the small gauge nickel chrome wire and re-winding it on a different material, I have shaped pieces of non-copper-clad circuit board material into a fat "T shape" with the bottom of the "T shaped" piece 20mm wide.  The upper sides of the T are just to keep it from falling downward will be trimmed off to fit the cover back on, so I just eye them up before cutting them.  The final trim is done with a dremel cutoff tool.  If all you have is single-side copper clad board, just put the copper AWAY from the resistor.

It takes two of these to wedge the resistor back to a flat shape.  I use a file to remove some of the material of one of the T shaped pieces so they fit just right.  These aren't particularly critical, you can see I just cut them out roughly by hand using the dremel tool and didn't even bother with a straight edge.  The "T shapes" fit in from the top behind the resistor and should press down and straighten the resistor so its flat.

The resistor should be approximately 150 ohms at the empty position, and should decrease in resistance toward the full position.  If it doesn't read exactly 0 ohms when the float is all the way up, it doesn't really matter.  This one only went to 15 ohms, and worked fine when re-installed.  The video shows how we checked the operation with an analog multimeter.

Once the resistor is wedged to stay flat, the wiper stays in contact throughout the range of motion.  The cover can be replaced and the tabs gently bent back over to keep it in place.   This type of repair has lasted umpteen thousand miles.

In the body air cleaner for the Vespa Large Frame

Perhaps this problem only plagues a large frame Vespa with the LML reed block engine, but I've been fighting oil-fouling of the stock air cleaner since my engine was kitted.  The throat on the reed block is very short with little length to keep high velocity oil droplets from backing up, the stock reeds (Which don't break hundreds of miles from home like the carbon fiber ones can) have a bit of spit-back.  This spit-back oil is coalesced onto the air cleaner, which restricts air flow.  Umpteen miles down the road after cleaning the air filter, and the bike is running rich again.  My carburetor is tuned to exactly, that it can't tolerate any loss of air.  Even changing the grade of fuel is a noticeable change in performance. 

So the only solution I could think of is to move the air filter out of the stock position.  This gives two benefits.  It leaves space for a velocity stack on top of the carburetor, and also prevents any spit-back from fouling the air filter.

I've seen alternate air box covers which give more space. I've seen filter elements inside the rubber bellows.  I've seen the bellows eliminated, and a pod filter used to suck up hot engine air and dirt from the road.  None of those solutions sounded like a good idea.  I wanted an air filter in the body of the scooter.  The air entrance at the front of the seat isn't the only path for airflow, so using that area isn't guaranteed to be all filtered air.  Right where the bellows attaches to the body is the ideal place to put a filter.  The challenge is that this space is shared with the petcock rod, the oil tank, and the fuel tank.  A soft foam filter with some length and small girth could squeeze in there.

I made a 3D printed flange with a clip to attach to the opening in the body.  I selected a Honda CT90 foam air filter element and closed off one end.  There was so much foam there, that I elected to cut the Honda element in half, and still have more surface area than the stock P200 air filter that I was running.  The open end was glued to the 3D printed flange.

The inside of the body is coated in a foam material, presumably for sound deadening, so a perfect seal isn't really crucial.  It took a little bit to push the air filter foam into the hole, and get it positioned so it was open in the center.

The result is very promising.  The performance is fine for my 20/20 carb.

Vespa Smallframe SIP VAPE electronic ignition

The SIP VAPE Performance Ignition obtained from Scooter Mercato is an amazing upgrade.  No more cleaning dirty points, or points that float at high revs.  The engine starts with barely a half a kick instead of several.

The schematic looks like this now.

Sunbeam (Hillman) Imp Water Pump Rebuild

 I bought a kit to upgrade a leaking Imp water pump.  The bolts weren't the same as the original and the shaft nylok nuts weren't even the same thread.

These were the parts that were in the kit that did work.  The fan belt was reinstalled with 1" deflection on the longest run for proper tension.

Seal = 5303290 N8020 S113

Bearing = 6202RS

https://www.rockauto.com/en/partsearch/?partnum=6202rs

Project Avanti Super Sport moped

Here's the new project.  This 2001 Avanti moped from Monto Motors Limited (Rajasthan, India) was in a friend's collection, and it recently became available for adoption.  This is similar to the Cosmo Motors of Pennsylvania also used Monto Motors to produce the Avanti moped once again and distribute the Cosmo Stinger which was a copy of the Avanti Super Sport.  The moped uses a Garelli VIP engine, and has the two-speed automatic transmission.  Our friend said this was a very reliable machine, and it actually has over 4000 miles on it to prove it.  It has some modifications (a 70cc kit, right-side, inlet manifold, and non-stock carburetor).

This moped is a tubular frame construction, with a top-mounted fuel tank, just like a little motorcycle.  It holds 2.5 gallons of pre-mix fuel for a very long range machine!  It is a lightweight, attractive-looking modern moped.  Its been re-sprayed at least once and will need refreshed for appearance.  The body panels and seat are easily removed for cleaning and paint prep.  The tires are original and will need replacement.

A morning with a toothbrush and some cleaning solution have removed twenty years of grit and grime from the frame and chassis.  A certain future-rider got his hands dirty in the cleaning process.

The mechanical issues are few.  It is well made, and the electrical system is functioning.  One operational problem is the shift point from 1st to 2nd gear.  The engine has plenty of torque in first gear.  It would wind out much higher in RPM before it really needed to go to 2nd gear.  However, the transmission shifts into 2nd way too early and starts bogging.  We are eagerly awaiting new "Double Duck" clutches with a higher durometer material to go into production.  I suspect that the original rubber clutches have swollen and don't shift at the right points.

The handlebar clamp was a little concerning.  The wrong bolts were used at one point, and the casting was not looking great.  I fashioned a stainless steel cover to act as a washer and provide extra strength to the casting.

A leak in the fuel tank was discovered.  It was just a little weep.  A repair had been attempted using some polymer material, but that had already degraded.  Luckily everything was clean, and only required some roughing up and de-greasing.  I've used this trick before to seal up pinholes in gas tanks, and it works very well.  I got my biggest soldering iron, and some good flux and just soldered up around the whole mounting bracket.  (Yes, solder will stick to very clean steel)  No more leak.

The general condition of the bike was "barn fresh" when we picked it up.  Parts had been re-sprayed at some point, and just didn't look good.  A new color was decided upon, and we went into full paint of the blue body parts into a new color.  We think it is very 1950's retro.

PHBG 15

80 Main Jet

(Needle bottom notch)

262AU Atomizer

42 Idle Jet

60 Starter Jet

K&N Air Filter

Project Vespa Smallframe - AC Horn

The sound of the original DC horn operating on the clipped AC through a rectifier and capacitor filter, just wasn't satisfying me.  It doesn't sound the same as operated from a battery.  There had to be a way to make the horn louder.  After all it is a safety issue.  If you blow your horn, you want to be heard.

I had purchased a 12VAC horn from India via eBay.  It is a nice build quality, but of course it was made for a Primavera, and the hole pattern was too small to fit the unique 100 Sport.  I had pondered this for months, and really didn't give it any action until this rainy weekend.

Since the reproduction 12VAC horn hole pattern was smaller, I could potentially graft it to the original 100 Sport horn cover.  This would require removing the rivets, and make a paper pattern of the adapter.  I could then cut out the adapter ring from whatever metal I happened to have laying around the shop.  I could use the same soft-aluminum wire to make replacement rivets to hold the whole assembly together.  I had nothing to lose, the DC horn could still be put back together if I wasn't satisfied... I had already taken it apart once before.

Things came apart easily.  No photos taken during the Dremel tool cutoff disc work.

I got to work drafting the paper model of the adapter ring.

Here are all the parts that will be used.

After crafting each aluminum rivet one-by-one, we have a completed AC horn mechanism grafted to the original horn cover.  It sounds nice and loud.

Genuine Stella Airbox Idle Mix Screw threaded plug

 For my friends in the Genuine Stella Owners Group of America.

This plug will thread into the hole in the back of the airbox and cover the idle mix screw.

See STL file LINK.