S50 Quattrovalvole; Slightly Higher Performance
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Ossessionato
09 190s taormina
Joined: 08 Apr 2010
Posts: 2045
Location: Googleville
Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Fri Oct 06, 2017 5:26 am quote
Backfires
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.
Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Mon Oct 23, 2017 6:31 pm quote
BackFires
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*
Hooked
Piaggio Typhoon 2013 (4t, 4v)
Joined: 23 May 2008
Posts: 113
Location: Montreal (Quebec, Canada)
Mon Oct 23, 2017 7:03 pm quote
Re: BackFires
Wheelman-111 wrote:
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!

20171013_104544_HDR.jpg

Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Tue Oct 24, 2017 4:42 pm quote
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.

PunkinSpeed99KPH.jpg

Hooked
Vespa LX 50 4T
Joined: 23 Dec 2013
Posts: 228
Location: Holland
Sat Oct 28, 2017 4:00 am quote
This is so awesome!
Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Thu Nov 02, 2017 10:27 am quote
Punkin Has a Nice Rack - and Takes a Stand!
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.

PunkinStandClose.jpg

PunkinStandDeploy.jpg

PunkinStandRack.jpg

PunkinStern.jpg

Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Tue Nov 07, 2017 4:00 pm quote
Pilot Jetting Blues
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.

PunkinJetStock35S.jpg
Stock 35"S" jet.

PunkinJet36_Stock.jpg
Side-by-side with the 36 Aftermarket. An extra turn of thread, and different nozzle shape.

Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Fri Sep 14, 2018 1:05 pm quote
AirBox Baffle Tube
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.

VespaAirboxBaffle.jpg

Enthusiast
2010 S50 Modified
Joined: 18 Feb 2017
Posts: 53
Location: Deepinnaharta, Texas
Sat Sep 22, 2018 10:03 am quote
Intake Snake Pipe Deletion
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?
Hooked
GTS 250ie Super, Italjet Velocifero, Scarabeo 150, S50,ET2
Joined: 22 Nov 2016
Posts: 275
Location: Winston-Salem, NC
Sun Oct 14, 2018 8:38 am quote
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.
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