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

62 Main Jet

(Needle 3rd notch from bottom)

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.

Project Vespa Smallframe - Toolbox

 So we've done an AC conversion to my best friend's Primavera.  It works great, but there's an empty spot where the battery used to be.  There isn't much space to carry tools on a smallframe Vespa, so I came up with an idea.  If I gut the dead battery and pull out all the plates, it would make a nifty toolbox.

So I rinsed the battery acid out several times while wearing chemical resistant gloves.  Then I took a dremel to the top of the battery case and separated it from the bottom.  I had to saw through the battery posts.

After knocking the inter-cell connectors apart with a chisel, I pulled the plates out and discarded them.  I found an old door hinge in the junk box and fastened that to the back of the battery case so that the lid would close down normally.  The battery-shaped tool box fits right back where it belongs and holds a few essential items in case a roadside repair is needed.

Project Vespa Smallframe - First Start DR130 + LeoVince

 After overcoming all the overhaul challenges I had my son help put the engine back into the frame.  We learned a few tricks along the way to help it go better if we have to do it again.  1) Put a short bolt or screwdriver in the opposite side of the pivot bolt to hold things aligned. 2) Put the drop-tail plate back into the lift after the engine is under the frame.

 Other than that the most fiddly part was stringing the cables back in.  I highly recommend fluxing the cables and soldering the tips so they don't splay out causing challenges with reassembly.

 The original main jet was a 74.  We started with a 90 Main Jet based on advice from friends with the same engine + exhaust combination.  The anticipation is that this will be rich and we'll have to move down.  Our close friend has an 85 main jet in his with the same setup as we are running.  We will see where we fall once we get through the break-in phase.

There is a smallframe build database, that I will consult.  http://sfs.alexander-hepp.de/

 And that's about it.  It took half a dozen kicks to get the gas back into the chamber, and now it starts up on the first kick like it always did before.  I'm genuinely pleased so far.

Project Vespa Smallframe - No Replacement for Displacement

 As the old saying goes there's no replacement for displacement.  Compression counts in there as well.  When taking the cylinder apart, i discovered what was causing the low compression.  The flywheel side gudgeon pin clip had come out, and the pin was gouging the wall of the cylinder.  I found three pieces of the clip, the others must have escaped via the exhaust port.  No more pieces were discovered when the engine was fully disassembled.

 

 The goal was a simply to install the DR130 kit, but upon discovering the damage, the whole engine had to be taken apart.  The gearbox was dirty, and the retaining nuts for the clutch and pinion gear were not torqued down.

 

 Saved again by Scooter Mercato a gasket and seal set came within the week so that progress could continue.  Unfortunately when starting to put things back together the head studs did not cooperate.  I don't know if they were a bad batch, or what.  I could not get them to torque down, they kept getting more loose.  That could only mean one thing.... they had stripped.  Despite being nicely lubed, they still stripped at less than 10ft-lb.  I complained to AZScooter Parts where I got them from, but it didn't seem to make any difference.  They said it was longer than 30 days since I bought them and shut me out.  (It is rare than a well planned engine rebuild is completed in less than 30 days, especially when I bought all the stuff at the beginning of the summer and rode all summer.)

 I bought another set of studs from a different vendor, but when the studs arrived they were the same brand as before.  I was not going to be duped again.  I decided to case-harden the threads by heating them to a nice cherry red and quenching them, twice.  They seemed to be adequately hard after that.

 

 Assembly went smoothly.  I decided to maintain the cylinder head temperature sensor, but didn't want to be bothered by the sensor under the spark plug.  The solution was to put it under the nearest head bolt.  There was very little space available to get the sensor and the torque wrench in there.  The solution was obvious... the smallest piece of casting fin between the head nut and spark plug was begging to be broken off.  So I just got in there with a set of pliers and snapped the sucker off.  Now there was plenty of room for the CHT sensor.

 

 I had chamfered the cylinder openings carefully by hand.  The ring gap clearance was in spec, the squish was acceptable, and this time everything torqued down properly.  I will welcome the extra displacement and some good compression.  A few little details were added.  Any place that the head shroud was fastened to the engine, I added a collar to the 6mm bolt.  This way there was a place that the bolt would torque down metal-to-metal, and not just on plastic.  I had done this on my Stella engine, and it worked well.

 The other detail was the shift mechanism cover, that I have never seen on a smallframe in the wild.  I got one cheap on eBay from India, but the mounting hole was in the wrong place.  I don't know if it was intended for a different engine model, or what, but drilling a new hole was easy enough.  The side where the neutral switch was located had to be notched out as well.  The original hole and standoff stud were easily removed and plugged.  Hopefully this keeps dirt out of the shift mechanism.

 

 

Project Vespa Smallframe - AC Flasher

 When converting to an alternating current system and eliminating the battery, the original thermal flasher doesn't seem to function very well.  They sell a "AC Flasher" unit, so I bought one.  The duty cycle isn't ideal though.  The turn signals stay ON longer than they go OFF.  I would like to have a little closer to 60% duty cycle rather than about 90%.

 The first thing to do was reverse engineer the circuit to see how it worked.  It seems to be a NPN BJT triggered by R C time constants.  The easiest thing to do is adjust the resistor values to achieve a better duty cycle.

 The base charging resistor is the easiest to change, and will affect the off cycle time.  Raising the value of this resistor from 8.2k to 30k should give a more even duty cycle.

Flasher Circuit simulation in action.

 I like to use the falstad.com/circuit simulator to test before committing to a change.

Here's the import source code for the simulator:

$ 1 0.0000049999999999999996 140.81048482046955 28 5 50 5e-11
t 272 144 320 144 0 1 -2.6125880249882747 0.6749068028310193 80 default
r 320 96 320 48 0 56
d 128 48 192 48 2 default
209 192 192 192 272 0 0.001 4.947513985652805 0.001 1
209 272 176 272 224 0 0.00009999999999999999 1.1314853841190933 0.001 1
r 272 80 272 128 0 8200
181 384 384 384 352 0 925.1509181977179 21 6 0.04 0.04
v 64 128 64 208 0 1 60 6 0 0 0.5
w 192 48 320 48 0
w 320 96 320 128 0
w 272 80 272 48 0
w 192 192 192 48 0
w 272 128 272 144 0
w 272 176 272 144 0
w 128 48 64 48 0
w 64 128 64 48 0
w 64 208 64 432 0
w 192 272 192 320 0
w 352 160 320 160 0
w 272 48 192 48 0
w 352 192 352 160 0
w 272 224 272 320 0
w 192 320 272 320 0
w 64 432 384 432 0
g 560 192 560 224 0 0
178 384 320 384 192 6 1 0.2 -0.021758635421366957 0.05 1000000 0.02 20 0.015 0.005 1
w 352 320 272 320 0
w 384 320 352 320 0
w 400 192 560 192 0
w 384 432 384 464 0
p 480 352 480 416 1 0 0
w 480 352 384 320 0
w 480 416 384 464 0
w 384 352 384 320 0
w 384 384 384 432 0
g 384 464 384 480 0 0
x 453 177 470 180 4 24 C
x 409 314 435 317 4 24 L1
x 82 72 108 75 4 24 L2
w 64 48 64 16 0
w 64 16 368 16 0
w 368 16 368 192 0
o 30 512 0 4098 10 0.1 0 1