Modern Vespa

http://www.jetsrus.com/a_jets_by_carburetor_type/a_jet_kits_keihin_selection.htm

Greetings:

Thanks BlueCloud. I have actually ordered a full set of main jets from some Scooter store but it's been 6 months or so and I don't recall the model designation of this CV carb. I guess I've been to busy/lazy to pull out my file and trace the supplier.

The off-throttle backfire fix for my Harley-Davidson was to go one size up on the pilot. Hopefully the same cure works here.

Greetings:

Since uncorking the Technigas exhaust - removing the aluminum end-cap restrictor - my little Vespa had acquired a case of the BackFires - one or two sharp "POPs" whenever the throttle was cut suddenly. I have posted that a larger Pilot cured Harley-Davidsons of similar off-throttle backfires, and hoped that the Vespa 4-valve 50/78 would respond similarly.

I was mistaken. I had a collection of Pilots from a Polini carb that was once fitted to my Honda Elite 50/72, but my smallest was a 39. Meh, why not try it?

Well, it sucked, to make a long story shorter. Not only did the backfires WORSEN, but starting, idle stability, and throttle response all suffered. Back to the drawing board...

I reinstalled the stock "35S" pilot, and increased the Main from 78 to 82. Whoa! No more flatulence, and SoPD* said top end improved considerably. I plan a top speed run tomorrow and will post results.

*Seat of the Pantaloons Dynamometer*

I have the same problem with my GP4!!!
I did a test by removing the rubber tube at the entrance of the air box and my speed has increased! But still the pffft by decelerating....
I will try the jet # 82!
Thank you!

Greetings:

I don't know how I messed this up. My swap back to the stock "35S" pilot was done along with a switch from a 78 main to an 80, not 82 as previously posted.

The result was a considerable improvement. No "Pop-pop-pop" any more when cutting throttle. Just a subdued single "Pop", about every other time.
Off-the-line and midrange acceleration had considerably more Verve, and top speed improved from a previous best of 58MPH to 61 and change.

DISCLAIMER: I have no way of knowing if the improvement is due to the jetting change or the cooler weather and a loosening of the new Malossi bore. Also, yes, the 61MPH top speed was a bit wind-assisted, but the scooter held a GPS of 60 even on the flat without wind.

From a Stock top speed of a road-blocking 39, the couple of hundred bucks and a pleasant day in the garage were well worth it to gain near 150cc level of performance from this little 50S.

This is so awesome!

Greetings:

Scooter Therapy can be very relaxing on my occasional days off. The noon-hour was dedicated to the installation of the Eye-Tally-Ann Faco rack and Buzetti side stand I got from ScooterPartsCo online, along with some pilot jets with which to experiment later.

The Rack's lower brace needs to go egg-zackly where Signore Piaggio placed the adhesive [b]VespaS sticker to cover the unsightly threaded holes. With a heat gun, taking great care not to overheat and blister the paint, I was able to salvage the plastic stick-on plaque and its adhesive and reapply it below the tail lamp.

I used some Industrial-Strength Adhesive-backed Velcro to pad the mounting points of the rack and possibly keep scuffing the paint to a minimum. The rack itself arrived without instructions and without fasteners, but fortunately my supply of castoff Metric fasteners is vast. (I always have a few left over whenever I reassemble anything... Now I can retrieve the Boy from school occasionally and have a place to bungee his huge-omongous backpack - now de rigeur in middle school. But I think I saw a little blood oozing out wherever Honda bolts violated the Vespa bodywork.

The Buzzetti stand is not at the same quality standard as the FA Italia rack. Instructions, paraphrased, said "Install it there". OK...

The bracket was stamped so that if you pull the stand out, it won't stay out. The spring geometry was wrong - who puts TWO springs on a side-stand anyway? Both pulled from the retracted side with respect to the fulcrum. If a careful foot wasn't utilized, it tended to snap back into retracted position with a Clack! This will not Do.[/b]

Fortunately it wasn't but a minute or two on the bench grinder and I got enough angle so that one of the springs crossed the fulcrum axis and holds the stand out - albeit still precariously. Then some Harley Davidson Frame Touch-up Paint to delay the rust on the bracket.

Honestly, don't buy this stand unless you have a bench grinder and plan on a little time - and some shim washers to get the stand angle to look right - to install it.

For some reason the other pics I took and emailed for editing didn't save - more later.

Greetings:

Part of the problem is the scarcity of information on these 4-Strokes. Honda's near-cult following for the AF16-generation engines found in the U.S. SA50 Elite models has led to hundreds of enthusiasts who have tried just about everything imaginable to squeeze 60, 70, even 80MPH out of an air-cooled big-bored 72cc Elite.

The stock jet for the 50S is that #35"S" jet pictured below. Who the heck puts a letter after a jet number anyway? Scooterpartsco.com supplied a 36 and a 38, the only slightly-larger choices I could find. But they're aftermarket, and I know from experience that aftermarket jets often don't perform like their Keihin counterparts in terms of nominal size.

So it appears with Punkin. Fitted with the stock 35S jet, my best idle was obtained at just over 2 turns out. Mounting the 36, I found it would barely start (engine already warmed...) at that setting. I screwed in to find it ran best with the mixture screw set at just under ONE full turn out.

With both jets, there's a stutter if the throttle is twisted rapidly off idle. I know there's an air compensation feature that's under ECM control, and it appears the computer doesn't quite know how to correct with the big-bore, cam and non-stock jets. It runs fine, but not perfect. Backfires still there with quick-cut throttle too, possibly a bit more... um, impolite but not as bad as with the 39 I briefly installed a few weeks back.

If anyone knows more about extreme fine-tuning these wee beasties, and perhaps a source for Gin-You-Whine Keihin pilots, please share.

Greetings:

Punkin motors on with 49mm cylinder, Polini variator and Malossi upgears, now with north of 1200 miles' worth of grocery-getting and dry cleaner runs. With the hot weather here in Deepinnaharta, Texas, I noticed more symptoms of flat-spots on sudden acceleration and an increase in off-throttle backfires. I surmised it might be running a tad rich for the thin, hot, humid air.

On a whim, and with a hint from Vermi, I removed the baffle pipe in the airbox the last time I serviced the box. WOW! Takes throttle without hesitation on the short run I could make during a break in the rainy weather we've had. I'm anxious to test, if only "Disturbance 1" would move along away from the Gulf of Mexico. (Sorry to Carolinians for whining while Florence is bashing you - Harvey last year means I know what you're experiencing...).

One downside (or upside, to some...) the intake noise is considerably louder with the intake tract freed from this pipe.

Greetings:

I've had a few rides since the deletion of the intake Snake pipe. Turns out this item was much more restrictive than it appeared. Furthermore, evidently Punkin was running rather rich, as I suspected. because opening up the air intake by that few square centimeters, plus losing the double-curve in the pipe increased performance tangibly.

Quick throttle increases WITH the pipe were met with one or two "stutters" where engine RPM increased but stumbled disturbingly - especially when a quick pick-up was needed to dash across or merge into traffic. Harley riders talked about "carb farts" with too LEAN of a pilot, but apparently non-combustible mixture causes the same symptom when the mix is too RICH as well. Anyway that symptom is totally GONE now!

There's still an occasional chuff - sometimes 2 - when the throttle is cut rapidly, but not the loud semi-backfires I was getting with the intake pipe installed. At least for this hot Texas summer, the 80 main seems to be OK. When it gets cooler - C'mon, Cold Front! - I may check the spark plug and consider that 82 again.

It would appear that this deletion is the remedy for the non-linear carburetion I and others have reported with the 78cc/Malossi cam upgrades. One issue; it's considerably louder on the intake side. Small price to pay or Big Bonus?

I have the Malossi cylinder, cam and GP4 pipe and was running with out the snorkel in the air box and had great performance. I was getting popping on deceleration so I bought a snorkel and put it I. I down jetted and tuned the carb again and performance dropped a little and I still had popping. I since have discovered a lek where the silencer joins the header. I need to resolve that. I am still tuning the transmission though. I think when I get back to that scoot I will pull the snorkel and retune, fix the exhaust leak and let you all know.

Greetings:

The Tecnigas pipe added during the build had started looking tired from corrosion and it developed a rattle. Purchased a Tecno Straight from a German vendor for $165-ish all in. The pipe arrived in 12 days or so.

The first thing I noticed was the substantial choke insert tack-welded into the head pipe. The documentation certified Compliance with all upstanding, wholesome and socially-responsible EuroUnion codes and laws for noise. And the washer (top and 2nd pic) blocking a full third of the header guaranteed the scooter upon which this exhaust was installed would never go fast enough to hurt anything.

So, obviously, it had to go. The Tec-No folks apparently would prefer the consumer remain in Strict Compliance with the party-pooping EU bureaucrats. Anyway that insert is ON there. Notched and tacked top and bottom plus a Tight press-fit. My 30 minute exhaust swap turned into 2.5 hours with all the grinding, sawing, notching and cold-chiseling needed to remove the thing without buffering the pipe end. Once weakened AND the pipe laser-cut with a carbide burr it succumbed to my slide-hammer and a blind-hole bearing puller. (Pic3)

The final 2 pics show the offending sleeve and the pipe opening with it removed.

Runs a little quieter than the GP4, not much. Torque at start is tangibly better and topped out at 60 despite 93 degrees here in Deepinnaharta Texas. That's actually better than last time out with the T-gas. Off-throttle backfires completely gone! I have a can of paint to match Punkin's orange for the heat shield. Will post up when complete.

Greetings:

The newest addition to Punkin's equipment list received a color-matched heat shield yesterday. The pipe works at least as well as its GP4 predecessor, and the backfires off-throttle are Entirely GONE!

Dah dah dah dah dahhhhh. I'm luuvin itt! 🍟

Greetings:

I'm sold on the Tecno pipe. Anyone considering a Tecnigas performance pipe for their 50cc 4V but daunted by the price should consider mine, though I feel the Tecno is a little better. The Tecno is a good bit heavier however. Packed-up Tecnigas in the box was about 9 pounds!

Awesome to see this thing running so well. Mine runs similarly and I've had +60mph days on mine as well.

Greetings:

Thanks CMK. Most of what I did to Punkin I learned from reading your posts. Thanks for that as well.

For now my attention is absorbed in restoring a new-to-me 2003 ET4, chronicled in General discussion. It's in 7/10 cosmetic condition I'll post a thread showing more Pics&Progress in Project Reports at some point.

Meanwhile Punkin is my go-to scoot for Dry Cleaners, Post Office, Grocery-Getting, Bank.... Deepinnaharta is mostly 40-45MPH roads with elderly drivers in Buicks and Camrys interspersed with Winter Texans in fifth-wheel haulin' HD Pickups. Punkin is plenty fast enough to stay out of the way

Greetings:

Weird behavior; Before I fire up Punkin from cold on the electric start, it ALWAYS requires 5 or 6 throttle blips to juice up the accelerator pump, or else it catches and immediately stalls. I've been playing a lot with kickstarters (My new-to-me 2003 ET4 Chronicles), and decided to begin using the kickstarter on the 50 occasionally.

The weird thing is that the 50/79cc also usually fires up on the first kick, but NO throttle-tickling is required. It just starts and runs. I wonder why?

Greetings:

Doing some reading and found a Service Bulletin suggesting my Punkin should have valve clearances checked at 1000 KM. Further research discovered sites that report the Vespa 4-Valve shims are 8.9mm in diameter. Before I sink $60 into a set, can anyone confirm? EDIT: Hot cams actually wants $89 for the SMALLER 7.48 size, and there no certainty that it's "
close enough" if the shim diameter spec is indeed 7.52

Greetings:

BTW once I get the shim set, I'd be happy to swap sizes with whomever needs.

I could well be wrong, but I thought modern Vespas all had screw-adjusted valve clearances, not shims?

Edit: Sorry for adding confusion. Interesting to learn the S50 used shims. (I just had a look at jimc's posted shop manual and see it mentions replacing "calibrated pads" to adjust valve clearances.)

Greetings:

Then again, This Site suggests a diameter of 7.52mm. Sheesh!

Greetings:

Shims for sure. Saved a pic from cylinder installation.

Greetings:

I found some shims at SIP, but if there is a Stateside source I would appreciate knowing where. Also can anyone confirm the 7.52mm diameter spec? Punkin and I would be grateful!

A very cool build sir. Thank you for sharing this with us.

Greetings:

You're welcome Soul Surfer. A little worried that I need to pull the engine again to check valve clearance due to Service Bulletin. At 1800 MILES, I'm far beyond the 1000KM recommendation I have read. Would need a handful of thinner shims at the ready, so need confirmed dimensions (7.52mm?) and a source that won't take weeks.

I don't know the diameter, but AF1 Racing (also in Texas) seems to have most sizes in stock (part no CM144319 to CM144333). Maybe they can overnight ship, or you may be close enough to drop by?

https://www.af1racing.com/store/Scripts/prodView.asp?idProduct=31787&sku=CM144331&description=CALIBRATED+PAD+-+CM144331&action=View

Greetings:

Berto is Da Man!!. Thanks brother. If anyone else (Or I, down the road) is looking for a US Source for "Calibrated Tablets, or Pads" - nothing as vulgar as valve shims on beloved Piaggio engine - the Page is HERE. No wonder it's impossible to search!

Greetings:

Along with my $15 used rim, a handful of valve sh... er I mean, Calibrated Tablets arrived to address the anticipated tighter clearance of Punkin's 4-valve mill, now with 1800 miles or so. Thinner than 265 I don't yet have - back-ordered, but will get here soon.

Any way to do this without dropping the S50 engine all the way out?

With the engine in it's possible to check the valves and if you have small hands maybe replace the shims. Probably easier with the engine out. I just checked mine when I had to pull the engine to deal with a pesky exhaust stud. The Ruckus I did the shim change on you just pulled the rocker arm to the side and replace it. My limited research with Mr. Google says you need a valve spring compressor to compress the spring so you can get to the shim or as you discovered upgrading the cam, just pull the rocker arms off.

Greetings:

Thank you PinkScooter. It looks like I'm better off pulling the engine out and setting it at a comfortable level, lacking both a scooter lift and small hands. Plus I'm inclined to drop things into places, nevermore to return. In addition, I just now happened to glance down at the new Tecno exhaust and saw... the empty hole where the lower bracket bolt is supposed to be!

Shining flashlight into the lower bracket, it's hard to be sure , but I believe there are only 3-5 threads exposed, suggesting the thing has sheared off under there. TOOL BUYING OPPORTUNITY!: Left-handed drill and sheath need to be identified and ordered.

I'll see if I can find the spec for the 8mm bolt length, and there's a spacer between the bracket and engine case - also missing... With three scooters, always someone clamoring for attention!

The Technogas sheared my upper bolt I attempted drilling it until I saw that the hole had some room before the sheared off bolt so I drilled it out to 10mm and tapped it for a 10mm bolt and it's better than nothing. As much as my housemate abuses it it's not long for this world. I just hope she doesn't take herself with it.

Greetings:

Another option! Thank you for that Pink.

Greetings:

Now that I have verified the shim diameter is 7.48 - one well-kept secret! - I found there are numerous affordable shim kits like THIS ONE on Amazon, fEeBaY and elsewhere. I will prefer to install the Original Equipment versions from AF1, but in the event my size choices don't fully match the clearance needs, I can still reassemble using one of these from AHL.

Anyone know if there's a Universal valve spring compressor somewhere so I don't have to pull the rockers?

I'm glad it's working out!

Personally, I'd stick with OEM shims ("calibrated tablets", excuse me ) too. I used to own a Suzuki GS500 that used similar shims. More than once I saw reports of people using cheapo shims that turned out to not have the right surface hardening. The shims flaked away over time and caused internal engine damage.

Greetings:

That thought crossed my mind as well Berto. The O.E. shims cost almost as much APIECE as the whole 47-piece set... Perhaps that says a lot?

I'd say so. You get what you pay for, and you don't want to wreck an engine over a few dollars or a parts wait.

I think you'd be better off buttoning up the engine and doing it twice if you really couldn't find anyone with the OEM size you need in stock and were absolutely stuck waiting for overseas parts arrival. Not that it'd come to that - between AF1 and ScooterWest (and no doubt others), I am sure you will be able to get any sizes you need in short order!

Greetings:

I received valve calibrated tablets from an Asian country with a Large population. The shims measured out pretty much the same as the Piaggio units for 47x the price. They were actually a little closer than the Piaggio parts on thickness though a little shy on diameter. It is possible they came from the same factory, based upon superficial appearances. Lacking the ability to conduct destructive testing, I will use the AF1 replacement parts by first choice, but confident that if I need to use thinner than the 2.55 I ordered from AF1, I should be fine with the AHL units.

Greetings:

Posting latest Punkin Pics.

Greetings:

Ms. Wheel-Person is the true Mistress of Punkin. She loved Flash 9, our red Honda SA50 SR (72cc Polini Contesta Iron sport cylinder and 9:1 gears.). But she absolutely ADORES Punkin. She enabled the purchase of the top trunk from a shop in Der Fatherland, at a cost of $175 US and waiting time of 10 weeks. I had almost given up and was considering stopping payment when it arrived, well-packed and intact in matching Taormina Orange. Probably just a few of these left worldwide. Fits perfectly on my previously-mounted Fa' Italia rack.

Now Punkin is just your average 61 MPH (GPS) Malossi 78cc Quattrovalvole, with a hot cam and gears. Torque peak seems to be around 9K but revs on to near 11K @ 61MPH - as long as there is a tailwind. Still does 55 all day long in any direction, approaching 2000 miles on the odometer. One foul note: The accursed clock battery appears to be fading fast.