Modern Vespa

There's only one option from here. If going leaner didn't clean it up, then it must need richer. Losing power while still having revs is a sure sign of being lean.

When the cables fixed. Keep going richer on the MJ until it gets better at 4000.

Hi Jack, and all, so back on the road again, everything else as before, put a 132 in and could not get it to the 3000 rpm range just splutter y as hell, 130, ok, so now its splutter y up to 4300 rpm, but as soon as it hit 4400rpm it clears & takes off.

It's the splutter at 4400rpm that needs to improve. Try 128 again.

Shouldn't be so spluttery low down. For normal too rich, up to 3000rpm it should be not so bad, then go really spluttery, until after 4000rpm, clear up, fly, then bog at high rpm.
Might be something else wrong. Choke might be slightly open, jet not seating, does happen.
Mark the throttle positions and post a video of slowly revving it from zero to max.

Hi jack & all
Well a crash course in audio/video for YouTube was a journey!
So here are the links, hopefully this all works.

I'm away this weekend so wont be able to do anything.

1 throttle position, 2 130 main jet up & down My street,

Good job getting the videos uploaded. Scooter looks cool. Would be useful to see the rev counter better.
Seems a bit lean. Sounding tinny. What size main jet causes WOT to not rev? Or WOT to rev lower than half throttle? The 130 is revving out fairly clean by the sounds of it.
Going to need a bigger pilot jet too. Can't remember if you're running a drilled filter or a vortex.

Also, if you could mark the throttle so that we can see the throttle position (need where the cable tension takes up and WOT on the bars, then a mark on the grip to align with those), it makes it a LOT easier to tell what's going on, too.

Hi Jack
Back from work. so
yes to vortex,
Rev counter, yep I know its a bit hard to see, tried too make it visible but the sun glare was a pain, just like the wind was with the audio

yes with the 130 once you get it up to 4400rpm it clears in the gear your in, shift into the next gear and its struggles till you get it back up to 4400rpm's again away it go's.
there's some thing weird going on in the transition.

Bigger idle jet, OK, we went from bigger which was a 55/100, to a 48/100

A couple of weekends ago tried while on its stand a 140 MJ, and it was boggy as hell to get the rev up, actually it couldn't. But that's on the stand.

tomorrow is a weekend for more exploration/trials, to test/answer queries.

Hi chandlerman, I have marked the throttle, (might be a bit indefinable) blue paint pen on blue, but its there.

Hi Jack
So with a 100AC it wont take of now till it gets to around 5000 odd rpm's and cant even get to that in 3rd
(this is all up &down my street)

Also then tried a 55/100 idle jet, that made things terrible, wont idle (even with the mixer & idle screws both fully turned in) and just spluttery as hell and wont take off at all, shithouse.

This sounds better. Reduce the main jet until it all cleans up. Easiest way to do this is hold it wide open. And see how high it revs out to. If way over rich, this will be under 7000rpm. If it revs much higher than this, there's something else wrong.

Hi Jack, sorry about the slow getting back, life stuff happens.

So at MJ 130 wouldn't get above 5000rpm
128 wouldn't get above 5700rpm
125 wouldn't get above 6200rpm
122 wouldn't get above 6500rpm
at about this stage the engine suddenly made an awful noise and lost compression, so Im going to drop it out and strip it down and rebuild it (when I get a spare moment)

Ill let you know what I find

You're having some awful luck. Something catastrophic going on at 6000rpm off load is highly unusual. Sure your rev counter is not set to read half rpm? If it were actually 12000rpm this would make perfect sense.
Will be interesting to see what happened. If the conrod snapped it's definitely an rpm thing.

Were you riding it or was it on the stand?

Hi orwell84
It was on its stand, as that's how I interpreted what jack was instructing me to do with this diagnostic process. put mj in rev it out see what rpm's it get to, then step down, do all over again. just like he said.

Hi jack yep to that,
in regards to rev counter I was monitoring rpms with both the onboard & a strobe/rpm light

Can't imagine what happened. Circlip came out? 6000 rpm is crusing speed. Can hold that all day long. If it was over 12000 rpm you would know it. With a full finned flywheel they whistle like a jet engine.

Yeah, I snagged a piston ring revving it on the stand, but it was over 8500 rpm.

Hi all,
Jack221 https://modernvespa.com/members/jack221
chandlerman https://modernvespa.com/members/chandlerman
Ray8 https://modernvespa.com/members/ray8
108 https://modernvespa.com/members/108
And others

Yes it's been awhile since I last posted.

And so Jack221, what happened back in March when it went kabang, was a ring tearing its self out of the piston. Made a bit of a mess it did.
So with work, family, and general life stuff, I'm finally getting back to this creature.
A SIP purchased of a new kit, the PINASCO "Magny Cours/ Granturismo" 190 cc like before,
with some other bits an pieces needed.
Then recently, someone I sort of know, in the neibourhood, Said's to me, " I've got some stuff I bought for a build but have gone a different path, would you be interested", new, never opened, a PINASCO "Vespone STX" 190 cc, Racing Exhaust SIP ROAD XL, plus a 24 carbie & a Pinasco large carb box cover, can have it all for $1000", "Ok" I say.

So I'm gunna have another crack at solving the mystery of the Vespone RX/STX/RB family.
So there will be questions, trouble, and strife.

Have recently been reading & going over my, and other peoples post's regarding this kit, and similar jetting issues, one of particular relevance/interest, was.
roody76, Vespa PX150 tuning issues. who was dealing with the same RX 190 kit. That was a journey with many varied obstacles along the way, taxing at times to keep up with the primary goal, but well worth the read, along with other post with relevance.

And so where I'm at right now is;
Pinasco 190cc Vespone STX Kit
jetting
Main stack: 120 BE3 125
Idle: 52/120
These I have measured and adjusted to true, for I found that you do not take on face value the designated values on the jets, they are just so off the mark, its ridicules.
Mixture screw: 2.5 turns out
(Rev's come down nice and quick after open throttle)
motor's config is
125/150cc LML Reed valve engine casings (Reed Valve, OK)
Pinasco Racing 80826 Y LK Long Stroke (60) Crankshaft (yes I know, I've been told)
26/26 Pinasco SI carbie (drilled to 2.5mm) SIP Part no: 40001100, with vortex, ON
(Do have a PINASCO bigger Airbox (PINASCO 25070131) (SIP Part no.: 25070131) also.
Vape variable ignition, timing set at about 22/23 BTDC
Racing Exhaust SIP ROAD XL, was (Ricambio Rapido big box sport exhaust (Scooter Centre)

Was a bit wondering what's happening with all the loose metal that Ive sent into the(Ricambio Rapido big box sport exhaust, not much has shaken out, thought, don't want the motor to suck something back up?
New seals, and great sustained results from leak test.

Oh and just for interest sake, gearing is,
Clutch 23 Primary 68

Gears Input shaft
1st 57 21
2nd 43 17
3rd 39 13
4th 36 11

So first test (Jack221) Reduce the main jet until it all cleans up. Easiest way to do this is hold it wide open. And see how high it revs out to. If way over rich, this will be under 7000rpm. If it revs much higher than this, there's something else wrong.
On the stand
147 slow to get to 6000+
138 it does get over 7000 eventualy
135 a bit quicker to get over 7000
130 Well, it gets to 8000, gets there quick & clean, let go on the throttle don't want to blow it up
128 same as above with less then full throttle
125 it gets to over 8000 at half throttle
122 half throttle quick to get over 8000
120 below half throttle to get to 7-8000

Next test
With scooter warm idle test
55/100 very wet pug 3 turns out mixer rev's come down immediately
Went down
48/100 wetish 2 ¾ turns out mixer rev's come down immediately
52/120 dry 2 ½ turns out mixer rev's come down immediately

Next test ride @3000rpm in 2nd then suddenly open to WOT, it accelerates immediately
@3000rpm in 3rd then suddenly open to WOT, it accelerates immediately
Did this for all MJ's 138 down to 118

So with a 52/120 120-BE3 and all those MJ
It really splutters pretty bad at round 3000rpm's up to 4500rpm's then it clears & go's. but if it under load in the 3000 range, doesn't splutter.
Its this splutter that I just cannot figure out

Appreciate any and all advise. Thanks

Well done for having another go. Will be reliable once Jetted better. Careful riding it lean. Try to do all the lean stuff on the stand.

If 132 main jet doesn't rev out and 130 main jet revs high and clean, then that's your jet to try on the road. If it revs out clean at wot in 2nd that's the main jet done. Also fit a BE4.

From what you've said AC120 BE4 130 and 50/100 is where to start road testing.

If you ride from low rpm while holding 1/3 throttle, until high rpm. It tells the whole story.

Edit: My quattrini will hold 11,000 rpm at wot on the stand. If there's nothing wrong, nothing will happen.

Where's ray??

Kinda tired of the "should be 160 air jets" conversation for tuned engines…. lol

Wanna save your time, don't use any air correctors that are 120.

Hi Jack221 & 108

120-BE4-130 48/100, I haven't got a 50/100, I have a 55/100, and a 58/100 (thats what it measures, it is supposed to be a 55/100)

Well this does feels like an improvement

So Jack221 this is what I know so far, on the stand holding the throttle at 1/4 throttle it rev's up to well up over 9000rpm , I didn't hang to find out how high it would get to in case the thing blows up in my face.

If it revs out clean at wot in 2nd that's the main jet done
Well regarding this test, WOT it splutters till it gets to around 4000/4500 then clears and takes off roaring its guts out, (it kinda like when someone drives a car in 2nd or 3rd gear and just keeps pushing the accelerator pedal down and the car is roaring its gut's off, and starting to max out and ya sitting there wondering why the silly bugger doesn't change gears)

Traveling up and down my street (my neighbors are gunna get sick of me) In 1st, 2nd, 3rd, from closed throttle through to before 1/4 throttle it splutters pretty bad, say @ 2000rpm's to 3500rpm's, but once I get to, and sit on 1/4 throttle and it get to around the 4000rpm it clears and accelerates (roars) away.

Oh and the plug is dry & dark chocolate.

On these carbs there is more overlap between the main stack and pilot stack than might be expected. Anything under 3000rpm is mostly pilot. Anything over 4500rpm is all main stack. However if the main jet stack is changed it does affect all aspects of the pilot stack, more than similar changes on a needle carb.
Try to ignore what happens under 4500rpm until the main stack is decided.

Someone on the German forum took a screenshot of Savage Scooter's Dyno graph...
AC 190 with a venturi and big air box
MJ 160
Wild.

So what's the issue with a too small AC?
It richens the mixture of course, but it also initiates the circuit too early.
With an also a too small pilot jet denominator, the two overlap to the point where no available cutouts in the slide will allow smooth acceleration, unless one chooses a pilot jet numerator too lean for closed throttle gear braking and "maybe" rolling to zero off sustained WOT.

I'm taking Jack's 120/BE4 suggestion as an insurance policy, but stop and go/in traffic riding will never be fun with that combination.

Again, on a LF rally bike the Vape Sport CDI should be switched out for the Road version.

So what your saying I need to do jack (Jack221)(IF 120-BE4 is now settled upon) is to make sure on the MJ for now?
So going through the range of MJ again with the BE4?
I have (measured) 138, 135,132, 130, 128 125, 122, 120, 118
I may be a few days in getting back Ive got some work lined up. And the weather has/will-be, been absolute crap.

Hi Jack221
I got your message, I have sent replies, hopefully Iv got it right still not quite fully familiar with this platform

Hello Leon, was wondering how you ended up with the Pinasco STX jetting, I've tried messaging your good self & Ray8 but maybe I haven't followed etiquette or I'm just not that tech savvy.

I'm currently running an RB177 (evo piston), Si 26mm vrx-r (with Venturi, big carb box, no bellows), Pinasco 57mm (110mm) crank, Pinasco Bull clutch, all in Pinasco rotary cases - timing @ 17*, jetting is 180ac/Be3/168mj + 55/100 idle jet, 04 slide, SIP Road XL (Megadella Compact L 92 is en route), with 23/65 gearing.

Hard to believe that even now the 168mj is still not big enough at WOT for this kit but I've temporarily paused the jetting journey until the Megadella arrives from Carmelo in Italy (great fella by the way). Choke test (a la FMP) & CHT's confirms this, if I pull the choke at WOT it's a noticeable boost, at 1/4 - 1/2 - 3/4 it has the splutter - all jets are KMT (for super accurate consistency).

My experience is in line with Ray8, it's gotta breath, Kevin (Savage Scooters) seams to do this, also W1R jetting formula 3:1 has pretty much kept up-jets linear (for every 10 on the AC it's 3'ish on the MJ, not 130 - 132 - 135 but 130+1+2+3 for example). There's no blowback, 1,000 - 1,100 steady tick over & it'll pull in 4th from 30 mph (3,000rpm).

I'm expecting the final carb set up to be something like 180 or 185 or 190/Be2 or Be3/170 55/100 - amazingly the mpg isn't as bad as you might imagine.

It's taken me 6 months to get to this & I've all but thrown the towel in loads of times but I've gleaned so much info from you all, Jack, Ray8, Ginch, FMP, Kev (Savage Scooters) etc…….I really am so grateful to all & I hope sharing this may give some affirmation as to the cumulative knowledge, wisdom, experience of you all has certainly not been wasted - oh I'm not a newcomer to the party as well, been twatting about with Vespa's since 1984, had the odd break. Hence the Pinasco theme that runs through this scoot, 1st scooter was a PK 50 ( with a Pinasco 90cc kit, up geared from a Primmy) all from Armandos in Sheffield (Guilio & Guido Pastorelli, Armandos sons sorted the Pinasco gear for this build from Italy for me at mates rates). Hard to fathom that Redcar '85 scooter run was 40 years this year still remember the Black Mariah Police van with a scaffold pole stuck in the side of it beating a hasty retreat, I'd have Thatcher's Britain back in a heart beat, we had hope it was gonna get better, now we're just f@#%ed. Heady days & certainly no wokeness bollocks.

Bloody hell I'm on a roll (waffling) but Leon this is what's worked for me & I'd be interested to know how you got on in the end, hope to get a reply & sorry for the long winded post. Andy B.