Modern Vespa

That'd be me

It's actually the discussion thread for the wiki page on the topic.

And 140/BE4/XXX should be your starting point for a tuned motor. You may find it's too rich, depending on numerous factors, but at least you won't seize it while you're figuring that out. The rule of thumb is to always (try to) start rich, then work your way down.

When it comes to jetting, Jack is the master, I just try to document things where I can.

The way I like to think about the air correction is that is basically sets a range for the atomizer and main jet, similar to the gear ratio in the transmission. A lower AC number indicates a smaller amount of air being added to the jet stack, which means that it effectively richens up the entire stack. The tradeoff is that with less air into the stack, you get less atomization of the air-fuel mix into the carb, so at lower throttle positions, it'll be less well mixed and thus tend to give less consistent performance.

There's also a reason that I said "1/4 Throttle is the Bermuda Triangle of Tuning." I guess it should really say 1/8-1/4 throttle, but the reality is that the level of precision you're looking for is going to be hard to come by with an SI carb. At lower rev's, the motor isn't pulling enough air to create adequate draw from the main stack. And because they're independent circuits, the idle is still in the mix, just making a proportionally smaller contribution as the throttle opens.

I haven't tested it scientifically, but from what I can tell, the main stack doesn't have linear uptake as throttle position and RPM's increase, either, so it's going to be inherently jerky. Don't blame me. Blame physics, with a dash of geometry thrown in because the universe hates us all.

There are some specialty atomizers that might be useful to you. I believe Ray8 has had some luck with them. I just give up and go side draft when I'm at that level of SI tuning, though.

As a bit of an aside...

First, on your carb, make sure the float passage is actually drilled. I have the tweaked si24/24e on my P210 and it had the expanded needle seat, but the float passage wasn't drilled. That shouldn't impact you now, but might cause you issues if you decide you need more than a 125 main.

Second, you'll probably want to run with no filter, just bellows to the frame, unless you live in a dust bowl. That'll help out a lot on the high end.

Third, isn't the Pinasco 80826 a rotary crank? If so, you're never going to get that thing set up ideally with a reed. You need at least a flowed crank, if not a bell. The bell will help a lot with low end performance, but at some cost of peak performance.

To answer Chandlerman:
I drilled the carbie out to 2.5 from original 2
open/no filter, using the machined Venturi funnel that came with the carbie.
Regarding crank, yes, well Ill just have to wear that.

And so the latest at this stage,
have found by replacing the BE3 with the BE5 with 120ac, 128mj, it run's the best so far with a reasonably colored plug.
May have a bit more of a play with mj range 125 to 132

But for now am packing the car & scoot for the trip to WA for the:
http://scootermille.weebly.com/

thanks for your help people

I'm glad you're in a good place for the Mille. Let us know how it ran when you're back in the real world!

Pinasco 190cc Vespone RX Kit
jetting was:
Main stack: 120 BE5 125
Idle: 55/100
Mixture screw: 1 turns out
idle screw: 1 1/2 turns (opening the slide)
(Rev's come down nice and quick after open throttle)
motor's config is/was
125/150cc LML Reed valve engine casings
Pinasco 190cc Vespone RX cylinder Kit
Pinasco Racing 80826 Y LK Long Stroke (60) Crankshaft
26/26 Pinasco SI carbie (drilled to 2.5mm) SIP Part no: 40001100
Vape variable ignition, timing set at about 20/21 BTDC
Ricambio Rapido big box sport exhaust (Scooter Centre)

Hi to everone/anyone, hope everyone is/has had a festive break.

Finally a bit of time to respond/update on this feed.

And so about 200kms out on the open road of the Mille "pshsss" holed piston. Pretty sure the MJ was way too small at 125, was running a 9 plug for the event, just to help. It was a bloody hot couple of days, I think last count, there was about half a dozen piston seizes/holed moments.

Have been reading some other forum feeds recently regarding SI carbies, and jetting, particularly this one I found who was dealing with the same cylinder kit,

Vespa PX150 tuning issues. roody76
Vespa PX150 tuning issues.

Reading this article posed some oddities regarding suggestion from participants on my forum, particularly jack221.
who encouraged roody to go with

The stock filter can't cope and has to go, run with either a vortex or nothing. AC120/BE4 is not for discussion. 55/160 pilot and main jet at 130 to start with. Hopefully you have the squish at 1mm. Timing set precisely. And a SIP 2.0 tap.

yet with me it was:

AC120 BE3 125+ 55/100 is minimum in a 26/26

SO Im waiting on the new kit,
PINASCO "Magny Cours/ Granturismo" 190 cc Part no 84119000

I had the 177 version and it was bomb proof, so Iv gone with this, the RX (now STX) seemed just too damn tricky.

Any feedback appreciated.

Must've missed this thread/posts previously.

But 20/21deg with a variable ignition isn't going to work.

You should be aiming for something like 23-25deg for most kits.

And I've learnt it's nothing to do with where the power of the exhaust kicks in and peak power.

But more to do with port timing and squish. So each cylinder kit will have a number in mind, static ignition and variable.

I think that's where most folks will be failing with jetting. Ignition has a huge influence over how it should be jetted.

A 9 plug isn't a problem, they're actually more suited for high revving applications (maybe end up with a sooty oily plug), and a 125 main seems ok too.

I was surprised when it suddenly went to the mille barely half way through jetting. I sent you a pm but was never read. Still in my outbox. Now deleted.

That RX was possibly too much for LML reeds. Was the cylinder wrecked? Usually just the piston. Worst case piston and a replate.

Hi jack, Na didn't see any message's, mind you I'm new to this platform so might simply never clocked it.

Cylinder did survive, a couple of days later I rebuilt the motor with a spare piston I had took with me, , but I wrecked/seized it (long story,my fault).
aluminum cylinder with nicasil lining.

To be honest this forum space is a bit like a kitchen full of chief's giving snippets of recipes out of their cookbooks. There appears/seems to be a failing in the coalescence & consistency in the advice, and/or whats offered is but a glimpse of the full picture (old saying the devil is in the detail) Maybe all the gurus should get together and construct a concise, complete, definitive text on the SI carbie's components & jetting nuances. A text that explains in detail the relationship/bearing of components with each other, & has detailed answers to questions, queries that can come up. (Like what Sticky's books have done for Lambretta's)
Would be happy to pay for that book!!

Group project… that ought to be productive.

one can only hope
Optimism

I built a VMC 187 with an LML engine, Si 26/26, Sip Road 2, 22t clutch cog and stock LML reed block.

Was great on the backroads, but could not maintain reasonable CHT's with sustained 90kph speeds. I tried to drive it to work once. It wouldn't have made it.

The answers given from the forum concerning this issue:

LML reed block too restrictive
22/68 gearing too short.

Btw, it ran well with the jetting we ended up with, with sputtering confined to 1/8 throttle.

I ended up putting a stock 200 engine in the bike (with a SIP R2). It handled sustained speeds easily.

When I revisit the LML 187, I will change to a 23/65 primary and a side draft carb.

Thread discussing my engine issues:

Figuring out my hot VMC 187-why and what to do.

I'm running 23/68.
Reed Valve Block LML SIP Part no.: 40311000
I had no problems with my motor when it was running the Pinasco Granturismo" 177 cc kit, did the 2022 Tassie Mille, nearly finished but crashed half way through the 3rd day, motor hummed along for three days till I hit a slippery patch, bloody shit awful wet weather for three days in hilly winding road country.

I wonder if the stock LML reed is contributing to the engine running less optimum? Are you using the metal reeds or have you tried other? Seems based on reading here over the years increasing the carb size from 20mm while retaining the LML reed isn't advantageous. Maybe Jack could comment on what carb is recommended for the Pinasco 190 with a LML reed?

I ran my BGM 177 for some time with LML reeds and a 24/24. Can't recall what jetting I had at the time but it ran cooler than anything else from memory.

What Leon briefly mentioned is that on the Mille this year there were heaps of holed pistons. Not sure how many as I wasn't there this time but was watching the FB group as people came through the checkpoints. "Suddenly lost compression" was mentioned again and again. Can't recall the last time I heard of a holed piston but suddenly there were half a dozen. Made me feel like this was fuel-related somehow... and the temperature was up to around 40 degrees C/ 104 F which no doubt made things more difficult.
Some of the scooters had motors that had run thousands of km in exactly the same configuration, including other Mille's.

Unfortunately optimism has never jetted a carb. lol

With persistence though, you can get there.

Well Persistence, is where I'm at!

Yeah, you'll need a few years of it…

Well the post arrived just after chrissy, with the new cylinder kit.

"PINASCO Magny Cours/ Granturismo" 190 cc, SIP Part no.: 84119000

Looks (& measures) to be the same cylinder as the 177 Magny Cours/ Granturismo, SIP Part no.: 84110000

Seems to me the only diff between these, the 190 and the 177 kits, is the thicker 1.5mm spacer gasket, & the 3703 head supplied with the 190 kit (replacing the standard gasket, & 3702 head) , the cylinders look to be the same cylinders.

So fellas (jack 221, Ray, etc) Im thinking does this kit need to be jetted as richly as the 190RX (STX) kit??

Ive got it back together, leak test OK, squish 1.3, put the 24/24 carbie (drilled 2.5) on, Vape (variable) set 23 btdc @ 2000rpm.

Have to say (as jack pointed out) the RX is a very different cylinder than others, as Ive observed with the two, porting engineering wise.

Would appreciate some direction with jetting.

When I had it setup to run the 177cc kit, I was running 24/24 (pre drilled 1.8 DRT), Vape variable 21 btdc @2000rpm, 160/BE3/122, 48/140, everything was tickerty boo. Did some few thousands of Klm's with out a blip.

any input is always appreciated.

Sorry, last thing I'm sure you want to hear, but you're going to have a tough time with that Sport CDI. The curve is too aggressive for a tourer.

SIP shopping cart :
Vape Road CDI
Lemarxon LM-L(1mm) slide
Lemarxon X234 atomizer
KMT MJ set in the 120-135 range
KMT Idle jet set in the 50-60/160 range

Yeah, the change of curve means much leaner jetting, which I'm not sure if folks take note that much with variable ignitions.

I'd definitely try Ray's jetting with the lemarxon. Seems to make a lot of sense.

Interesting you say that Ray, Ive had this ignition on the scoot for quite a few years now and hummed along nicely.

The suggestions you offer are fairly lean in contrast with all the advice given before for the RX kit. Is it because this kit is not as demanding? Am I right in surmising that the cylinder is the same for both Granturismo 177 & 190 kits?

Now here's a strange thing, Ive been away for a few weeks so this weekend got back to start getting the scoot running, (got it all back together before I went).
It wont idle unless the idle screw is 2 -3 turns in, and if you turn it all the way in, it only idles a bit more, it should be racing, thoroughly cleaned the carbie & even tried a couple of other carbie's, same behavior, its got me stuffed as to whats going on. Ive just thrown in 55/160 140-be3-125 to get it started. its absolutely gutless at 1/4 throttle but once you get the rev's up for the main stack to kick in it fly's. I thought maybe the idle circuit might have been blocked/restricted, but not after cleaning, and three carbies. ??????

Sounds like it too rich.

What's the squish at? That'll determine the ignition timing, and then jetting.

And still with the vape sport?

I haven't heard this one before. Can you give an example how this might work?

The easiest way to get this jetted is, keep the RX jetting and reduce what is too rich.
Too rich means splutters like the choke is on. Any other noise of or feeling is too lean. If it is actually ridable through the spluttering, it's not actually that far too rich. Once you find the ridable, yet too rich point, what to do next is pretty clear.

Hi
As mentioned a couple of posts earlier, squish @ 1.3
Yep with the vape sport. in the past have always had the timing set at 21 bftdc, taking into consideration your feedback, that it should be at 23bftdc, that's where its at now.

There's a squish to aim for, for each kit. Usually instructions say it's 1.3mm, if you end up tighter or bigger then the ignition should be adjusted to suit.

So if the kit is 1.3mm, variable ignition 23deg @1700rpm, with 1.35-1.4mm you would aim for 24deg.

And the same for static ignition, which most kits are aiming 18deg @1700rpm.

And with a tighter squish and later timing, jetting is leaner. 24deg goes richer.

You're jetting the curve too.

I just spent the past 3-4 months on and off playing around with various engines jetting and timing, malossi 210s with si carb, ones without. And even using my smaller as a guinea pig.

I think that's why most folks end up going in circles with jetting. Things aren't setup quite right.

Apologies missed that, I see it now in a previous post. Yeah, I'd aim for that timing.

I'm a little surprised 55/160 140-be3-125 wasn't an improvement.

I'd downsize the pilot and see if things improve.

Most malossi engines I used the same numbers as you (bigger main…)

Hi jack
Whats your thoughts on the idle screw issue I mentioned.

Just to sus things out a bit (this is in the back yard, on its stands) I put the leanest idle jet in I had 35/120, it would just die at 1/4, then I worked my way up to 55/100 to see the effect it had. It would just not take up at 1/4.
(All the while checking at each stage to see if the idle screw when turned full in would course the motor to race, it didn't'.)
Untill I got to around the 55/160 mark. at from this point the mixer screw has little to no effect. At 1/2 to wide open throttle it fangs.

Forget about the idle jet and atomiser for now. Focus on the AC and the MJ first. Both of these affect the idle circuit wildly, so no point wasting time on the idle jet.

You need to get the MJ big enough to pull the loaded rpm down when you fang it When just too rich on the MJ, 2nd gear full throttle won't rev out, there's a big cloud of blue smoke following you and it won't go. At this not revving out point you know you're safe. Two main jet sizes down from here and that's the main jet and AC done.

The biggest issue is if you're at 23 advance at 1700 you're also close to there at cruising rpm. That's fine riding around town, but if you're long-ride touring you're risking a holed piston/seize. I couldn't jet or retard my way out of that CHT 20 mile+ creep.

That shopping cart suggestion is not lean. Andreas (aka Lemarxon) has cracked the code running a kitted bike with the SI not made for tuning.
Best of luck!

If you relook at your cruising rpm… shouldn't be lower than 4000rpm.

I'd be surprised if anyone is riding around above 50km/h in 3rd/4th gear that's hitting less than that 3800rpm

It's around 24.5deg @4000rpm (max advance) which I'd feel safe with.

I'd tried 26deg with the malossi 210. Great off the line, but jetting was a bit of an issue and engine got toasty when coming to a stop from cruising in 4th gear.

Ah sorry for going off tangent…!

Yes, good luck Leon!!

Hi Ray & 108
so in-regards to timing, sounds like its better to have it retarded at around the 20-21 mark, that's where Ive been at for the last few years set, at 20/21 at 2000rpm.
That 1mm slide is really expensive,
https://www.sip-scootershop.com/en/product/throttle-slide-lemarxon-low_84951000?usrc=Lemarxon

Could i just file the slot out to 1mm?, I have plenty of No 4's, or are they talking about the scolloped cavity on the bottom of the slide.

Hi jack
So go with the same setup that was with the RX 120 Be3?

Nope I'd still aim for 23deg at 1700rpm.

So you'd max out at around 24deg @ 3400-4000rpm

And assuming you rev out to 7000rpm, it will be at around 18deg.

Of course you can time later, but most likely you'll have a lack of power then what feels like a rush of power.

Been there trying to modify jets/slides to be bigger or leaner… doesn't work. You just can't get enough accuracy. I think the hole in the slide is maybe doable… but the scoop I doubt could be accurate enough.

Start with the same as the RX but biggest main jet you can find. 120/BE3/145? And hopefully it won't rev out and splutters. If really way rich, as you open the throttle from 3/4 to full, it will drown and cut out. Let off the throttle a bit and it will restart.
When this happens, you know where you are starting from.......safe. Then the jetting begins.

Hey fellas, just wading into this thread. It's touched on some things I was always a little hazy on.

First off, there's mention of 1700RPM being the target for setting the ignition timing. Me, I usually time it at wherever the engine settles with the idle adjuster cranked in -- about 4000. Elsewhere I've heard tell of *peak torque* being the correct point at which to set the recommended timing, which in my own case would be in the high 5000's. Now, my static VAPE ignition only advances about 1.5 degrees from 1700 to 5000, but that still seems like a big enough spread to count. Anybody care to weigh in?

Second thing I wanted to ask about was what 108 was explaining, the relationship between timing advance and squish. It appears (though I could be wrong) that bigger squish = room for more timing advance, as much as 1 degree per 1/10th of a millimetre (!). I'm running a Malossi 221 sport, and that's got a recommended squish of 0.8/0.9mm. Buuuuut, because somebody on the internet told me to, I set my squish at 1.2mm. Does this mean I might be able to safely advance timing to 21 BTDC? Or even that I should?

FWIW this is my daily driver and *also* my long-haul bagger. Fast is good, reliable better.

But how's it been riding it so far..? It's tuned good atm?

Riding pretty well. Better than ever before, at least. It doesn't pink under any circumstances now, which was my original goal. Now I'm chasing after smooth acceleration, any remaining power that might be hiding somewhere, and if I'm lucky, some reduced vibration. Bonus points for improved fuel economy.

I think I'm still minorly rich in some spots. And too lean at 1/8th throttle -- this Lemarxon slide I bought, without the notch under the bypass orifice, leads to a lean stutter when rolling off the throttle at 80km/h. I'm thinking of filing out a mini-notch there.

But yeah: I'm almost there. The current setup's done 6000km or so, much of it with 500+km days. It never complained.

That's where I ended up, trying to make the best of a racing curve on a road bike.

They're talking about the cavity. The slot is actually deleted.
And you can't just get an atomizer or a slide alone. The slides and atomizers work together. You could make your own X234 by soldering closed the bottom holes of a BE2, but without that $$ slide it will not be easy to get it to work.

I would put the 04 slide back in and up the pilot jet by a lot. 10 points at least. Stuttering on the rundown means it's very lean on the pilot jet. As it's been running a long time it means the main stack is closer to correct.

(Ready for a long post...?)

Thats great you have a dependable, ridable scooter though. Not sure if you want to be chasing a moving target. Everyone has different needs and wants from their scooter...

Sounds like the slide is compensating for the rich setting.

Like Ray mentions, Lemarxon setup sorts out the short comings of the Si carb jetting issues, in which:

1. the main jet feeds the pilot (instead of an independent feed from the fuel bowl)
2. more importantly, the lack of midrange jetting (that was never really needed on a 12HP engine)

with a aftermarket kit and the need of extra fuel, you either have super rich jetting of the main stack and pilot, which is boggy and smokey at traffic lights, or where i think most people land, rich but ridable main stack, and a lean pilot/idle setting to off set the rich settings of the main. thats probably why most folks are idling high after a ride around the block and have heating up issues (and stuttery lack of power) which you end up going around in circles with cos you're thinking the main stack is too lean and end up with a 140 main... I think the malossi instructions are a little extreme where its a revvy engine and ignores (1. daily riding (not expecting to stop at traffic lights) and 2. expecting the kit to be disassembled/maintained every 1000kms). everyone I've discussed with (add your favourite german or italian vespa builder in here...) ends up at the basic 1.3mm squish (and I think most kits are aiming for that number now). Of course you can run a 0.8mm squish, and ignition timing according to max torque, but jetting and timing that engine for all types of riding (idling at lights...) will be challenge at best, I've never made it work.


With squish I usually think about it in 2 ways:
1. safety/heat tolerances, so when things get hot, things expand, piston doesn't make contact with the head. 0.8mm seems great for smaller cylinders.
2. good stable compression "space", the cylinder has a sweet spot for its size and design, so not so tight (yes, we all want amazing compression) that you get pinking and preignition, thats where the larger squish of 1.3mm helps out but good enough compression where it generates good power. You can get a lower compression head to eliminate pinking especially for its a tourer.

With the optimum squish there is an ignition timing needs to go off to give the fuel/compression to do its thing before gases escape down the exhaust and scavenge back. If your timing is too close to TDC (lets say 20deg, there isn't enough time for the fuel to be burnt whilst being compressed and you're getting wet unburnt mixture down the exhaust which gets sucked back into the cylinder over time (yes you'll run cool because you have a bunch of unburnt gases flushing the cylinder and exhaust). That's when you can adjust the jetting to compensate. But why do that when we know the more advanced timing is the more power and torque can be achieved. It's just a case of seeing how much the advance can get away with and how it retards and if the carb can be jetted accordingly. And there's a balancing act to this, because more advance = more heat, which can be addressed with jetting and air/fuel mix screw. With variable ignitions you can get away with advance timing and have it retard so things don't get hairy fast. Granted with that, it needs to be jetted accordingly, hence jetting the curve.

For Malossi 221 engines I set it after this epiphany, Vespower (polini idm etc) 24-25deg, for Vape sport 23-24deg. All with 1.3-1.35mm squishes, jetting the carbs made much more sense afterwards.