Modern Vespa

Hi I am looking to find out some info on how others have jetted their scoots around the Pinasco 190cc Vespone RX Kit

Current jetting
Main stack: 160 BE3 125
Idle: 52/140
Mixture screw: 2 turns out
idle screw: 1 1/2 turns (opening the slide)

(Rev's come down nice and quick after open throttle)

My motor's config is-
125/150cc LML Reed valve engine casings
Pinasco 190cc Vespone RX cylinder Kit
Pinasco Racing 80826 Y LK Long Stroke (60) Crankshaft
24/24 DRT SI carbie (SIP) (with holes drilled in filter) SIP Part no.: 400000T5
12V Vape variable ignition, timing set at about 20/21 BTDC
Ricambio Rapido big box sport exhaust (Scooter Centre)

I can't seem to get it clean around 1/8 1/4 throttle, it splutters.

Really appreciate any constructive feedback.

Leon

ignore this, posted wrong.

So im assuming its too rich on the pilot? Just to confirm this, try putting on a tiny bit of choke. Does the gurgle get worse or clean up? If its too rich, maybe the following based on my faffing about with my DR177.

How about change the pilot to 50/140? Its marginal change on ratio, you would be going from 2.69 to 2.80 (bigger the ratio, the leaner its heading) but maybe this little change enough to iron the gurgling out. I had this on my DR177 at tiny throttle, kept experimenting by going leaner in steps using a few pilot jets then adjusting mix screw until i got it acceptable to me. Its not fully gone the gurgle but the general running of my scoot is happy all round so I would rather live with it.

Head to this post Calling all tech heads! Si Idle jet question(s)...

Change the air corrector to a 120 before it gets ruined.

Is it spluttering under load, as in accelerating, or maintaining speed up a hill, or is it spluttering when there is no load, as in coasting, or decelerating? If it's under load, that is actually a lean bog and you need a richer mixer tube--that means a BE5, or possibly even a BE4. If it's not under load, welcome to the club. In my experience with kitted LML reed motors, it is impossible to get rid of that off-throttle fourstroking completely. Fortunately, it is purely aesthetic and has no impact on performance.

The best you can do is make sure you have right-sized your main jet so it is no richer than absolutely necessary (I presume you know how to do that by testing for splutter at WOT in 2d gear). I have found that these LML reed motors want leaner jetting than what you usually see posted here. I am running an AC160/MJ114 combo on my 177 (MJ113 in hot weather). I would expect your AC160/MJ125 combo to be pretty close for a "190", but testing will be the final proof.

I haven't tried this yet, but another thing that might help is an idle jet with a 120 air hole--such as a 45-120 (very rich) or a 40-120 (medium rich). Supposedly, the smaller air hole results in less overlap between the idle jet and the mainstack.

May I also suggest earplugs? I recently went to a Malossi box exhaust and, while I am enjoying the performance, it is loud. That drove me to start using earplugs and, with them in, I can't hear the off-throttle fourstroking at all.

My DR four strokes at 8th throttle too and nothing I can do . I got used to it but I'm safe in knowledge I can cane the scoot WOT and everything perfect . If you shift your gear up when it gurgles it won't gurgle so much , it's generally 1st and 2nd on mine it's worse.

I have a similar setup although rotary. It's been suggested to use a 120 air correction to minimize the addition of air. Seems like you could be close as it is but may need to adjust if you change out your 160ac for a 120. My current jetting is 120/BE2/125 main stack and 48-100 pilot 2 turns adjusted on mixture. The BE2 made best midrange performance.

You can't jet that out on a kitted bike and still supply enough fuel when you close the throttle.

At barely open throttle you uncover the progression hole.

The two channels overlap, and it four strokes until the mixture screw circuit tapers off.

You could put a leaner jet there and it will feel better.
But at closed throttle it will be too lean.

Hey thanks folks, some food for thought. lots of mixer tube suggestions.
Just to confirm, what I understand, BE1-rich---progressively leaning out through to---BE6-lean.

Jack221: OK, I have read before a 140 to 120 suggested for 177cc upwards. 120 sounds rich, happy to try.
Kowalski: Ray8: It splutters when I'm coasting, say at 1/8 up to 1/2 throttle, then when I give it the throttle it splutts a bit then takes off, love's it open throttle.
ferriswolf: Have already come across, & read/printed that thread,thanks. Will try your choke suggestion
hibbert: Your jet config for Main stack, rich lean rich, idle does sound rich. Interesting

They are not numbered sequentially from rich to lean. Far too obvious a ploy!!
The best explanation I've heard so far is that they were simply numbered in order of their production... which clearly doesn't help.

Here's a couple of images to ponder.

Cheers - (Michael from Ballarat)



[/url]

Hi Mick
I think I have come across these images before somewhere/sometime in the great continuum of life, and so larger rich-- smaller lean??? or vice versa???

It depends... they are mixing tubes or emulsion tubes, one part (the top part shown in the picture, they're upside down) lets in fuel and the other end lets in air. I guess I was pointing out that the system is not really numerical.
I think the chart actually makes more sense than the photo, allowing you to compare different parts of the rev range.

I seem to recall also that the standard LML idle jets are very rich from the factory.

AC120 is not the richest. And may need richer. The 190RX is not the usual 177 kit and needs more. Atomiser will be BE3, forget the rest for this. Pilot jet 50/100 and go from there.
Pinasco pistons have zero tolerance for running lean but set up correctly last forever.

Been playing around all afternoon (roaring around the hood) trying different combinations.

So far as of, Seems better
Main stack: 140 BE4 118
Idle: 52/140

Jack221: Will have a go with A/C 120, hopefully when it come in the post tomorrow. Don't have a 50/100 (2), do have 48/100 (2.08). See how i go.

cheers

The main jet meters all fuel to the engine.
You've leaned the pilot circuit (feeds off main stack fuel well) with a smaller mj, so it feels better.
HAS to be too small for your setup.

You were spluttering while coasting at 1/8 throttle because it's not under load. Short shift and it should clear, as load likes rich.
Don't try to jet that 1/8 splutter out if you want to be able to coast or gear brake with a closed throttle on a long ride.

Countless pages on this subject.
Would in fact suggest….no, you can't jet an Si on anything other than completely stock.
I can see why the average punter gives up and buys a GTS.

You can eventually but it's the explosions , seizing , lots of cost and generally being naffed off with the countless problem of carburettors. But hey that's all part of the fun allegedly 🤣🤣🤣

And inexpressible happiness when finally everything works as it should and drives great. It's worth fighting for

Hi
So tried hibbert's 120/BE2/125 main stack suggestion, that was worse.

So at the moment
Main stack is 140 BE4 120
Idle 48/100

Seems pretty close, throttle from 1/2 onward to full tiptop, the spluttering is still about a bit when getting off the throttle, coasting.

Hibbert did not use a BE4. This is way to spluttery low down which will cause you to think the top end is good, when actually dangerously lean.

Came across a thread that's on MODERNVESPS.com
Titled
"Wiki [D] Si jetting Chart + How to Tune an Si Cart"
He's recommending any thing 177 up should be starting at 140 BE4, no less.
Don't know who wrote it cant find a name, did print it out for ref. tho.

Jack211 Thanks for your feedback, so which should I be trying, the 120A/C or upping the main jet,
I did try a 125 with 140 be4 thought it sounded not as clean as a 122 120

cheers

Has the carb been drilled? Referring to the fuel passage from the float bowl to the main jet gallery? Most tuned engines will require this modification for sufficient fuel supply. It's common to drill the passage from 2.0-2.5mm.

In your original post the complaint is sputters at 1/8-1/4.

It's been my philosophy to use the maximum main jet as performance allows.

I had similar results to yours with 120ac and BE3 had to reduce main jet to 118 to have satisfactory performance in mid range. I suspected not enough for WOT.

This is why I tried the BE2 mix. This arrangement in my engine seems to run clean in the mid range and uses a larger main jet. Last week after running a 125 main jet for the last 8 months I detected a slight richness when the weather turned warm. I went down to a 122 main and cleaned up minor main jet bleed into the mid range. This sounds like your description of the tests with the 120ac and BE3 taking you down to 118 main.

SO after a few days with a box of Jets and reading other post of Jack221, Ray8, roland87 and others

Im in a state of fuckedness, is this splutter caused by being too, LEAN or too RICH????

Here is a recording of my scoot and the spluttering bullshit I'm trying to deal with, there is also a pic of the page of combo's that iv tried.

I undestand that you wont get it all out/cleaned up, but this is too much!

And before anyone throw air leak comments, is definitely not displaying any symptoms. that I'm aware of.

I can/have cleaned it up a bit, by going down on main jet to 120 but then doing the mad flatout KM then clutch in cut motor look at plug test it's too light for my liking.

Current config Si 26/26 (bowl hole drilled from 2mm to 2.5mm) SIP Part no: 40001100 I swapped from the 24/24 because this has been drilled where the 24 was still at 1.8mm
Main 140 BE3 135 (It HATES 120, really )
Idle 52/120
idle come's down quick and clean

at 39sec on recording is where I give it the full throttle in 3rd (sorry about the Bloody wind)

https://www.veed.io/view/1fd946d9-28db-44cb-aacf-7b6fbeb9ac1d?panel=share

Let me know if this link works, or not.

It's all too lean. Seems like your trying everything but the right thing.

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

I bloody well know, it feels like it's/I'm all wrong

OK jack,
I don' have a 55/100 or 50/100 (their the only two I don't have)I do have 48/100 and the rest, Every time I put a 120A/C in it run's shithouse.
So did the sound link work, if it did what is it I"m hearing, splutter because its lean or rich, due to which, Idle or main stack???

Or should I go back drill out the 24 put it back in?

Ok jack, just wacked a 120 BE3 128 and the 48/100 in, and flew around the block (about 3km or so, straights & hills) between flatout throttle and 1/2 to 1/4 still shit, turning the throttle on, but love's it flatout.

is this due to the Idle jet,? could I drill it out??? (bottom hole) & what size would the drill need to be is say 48, 50, 55 meaning .48 .50 .55 of a 1 mm
Or do I head back, drill and put back in the 24 .

More accurate with the pilot is to get a 55/160. Soft solder the air hole closed and re drill to 1.0mm.

Good it's getting better, going the right way now. Once a 55/100 is in, reduce the main jet to adjust the 1/3 throttle splutter and see where it ends up.
Don't do too much wide open until we know where we are.

On board

Ive put the word out to some friends to see if they have any of the jets 50/100 55/100 about on them, other wise Ive got a few 55/160's I can mess with if need be.
I'm assuming that the tapered hole on the bottom of the idle jet is the smaller number (48, 50, 55 etc) if so, it might be easier to drill it out from .48 to .50 .55 of a mm, and not have the worry of a if'y solder coming lose. just a thought.

Wondering would I still need to be going this rich with the 24 carbie ??

I don't have any feedback on the 26mm carb no experience although it seems your 24mm might have some modification. My untouched 24 was like 1.5mm out of the box. Initially I drilled it to 1.8 then 2.0mm.

You can drill the fuel hole with measured bits. Put the bit in a vice and twist the jet by finger. The mj and ac can also be drilled or reamed. Many bits are not what the stamped number says, btw. Mj's to try should be compared to each other with a tapered needle.

Are you adjusting the mixture screw after each jet change?
Mixture screw adjusted for smoothest acceleration in 2nd gear from a rolling stop, after adjusting for highest rpm on the stand and backed out 1/2 to 1 turn.

Yep it was a DRT modified carbie sold by SIP 2 ver
1 for 177kits (1.8)
1 for 190 kits (2.0)

Yep each time I change anything I check/adjust the mixer screw

I listened to the sound clip again and it doesn't sound that bad maybe slightly rich just as you mention on take off.

I looked up the Vespone because I wasn't sure which one it was. It looks more advanced than my cylinder the Two side transfers are substantially larger, the piston is more skeletal and center plug head. I'm assuming the case transfers are port matched?

Also looked up the Pinasco VRX-R 26mm with intake funnel (velocity stack). It mentions it has a COSA float cover but I didn't see a mention about the fuel passage to jet gallery might be worth confirming that bore size with drill bits as gauge's. Seems like a good choice after seeing the size of the Vespone transfers. Are you running with the velocity stack? The intake funnel should increase main jet size.

Have you done a flood out test? Using this method to quickly find the too big point and then fine tune from there. Using Ray's description 'from a rolling stop' in 2nd gear what maximum main jet size that will not rev out? Usually the main jet will be within a few below that. Might begin with a 150 MJ so you can feel the obvious to some splutter. Typically it will be overly rich then clean up momentarily and then splutter again in high range. Working your way down until the high end splutter goes away. If you stay focused on just 2nd gear from a rolling stop the close to correct size main jet should pull 2nd clean from bottom to top. At that point it's fine tuning which for people like me still requires lots more trial and error of many more things.

That is generally the starting point then fine tuning the mixer and pilot. I would do that since you have switched to a larger more sophisticated carb.

What reeds are you running?

So after a week away, back on the tools

Main120 BE4 125
Idle a 48/100 drilled out to about 56/100 (was trying for 55)
drilled filter off, venturi on, carbie
mixture screw 11/2 turns
Running a hell of a lot better, still a bit splutter'y on the throttle when coasting (giving it a little bit of throttle) but when you give it a bit more away she goes.
At this stage is it still possible to clean up????

Change the BE4 to BE3 and re adjust the mix screw, then it Will improve some more.

Jack, yes well that did clean it up some more, but when I just did the 1km flat out dash, cut motor, check plug, its a lot whiter than with the BE4 (milk chocolate) its a bit worrying. Do I need to go up on the main??

Leon from memory the venturi comes with (or used to come with) a 140 main. 125 sounds about normal-ish for your state of tune. But the venturi's job is to draw more air, so more air = less fuel in percentages. Could explain the white plug.

If flat out plug chop, then you're checking the main jet why change the atomiser. Put in the BE3 and adjust the main jet. The atomiser may need changing but needs the main jet near correct before it can be assessed.

On my kitted LML (Malossi 166) I finally gave up on the SI carb and autolube and went with a PHBH 28. It is smooth as butter across the whole throttle and rev range. I think sidedraft carb is the best and easiest solution, though you will have to figure out how to mount one to the LML reedblock or buy the four-petal reed block/manifold kit from SIP.

And so still retaining 120 BE3, went from 125mj to 130mj then 135mj finally 140mj(that's the biggest Ive got), at each increase of the mj the spluttering ( this is at the point where giving it a bit of throttle to coast, once you then give it more it then pulls through it and cleans up) increased more, (wide open throttle on all the jets fine), but on the 140 the spluttering is quite obvious
At 135mj, its there but not as pronounced as at 140mj
The pic shows, doing the 1km flat out dash, cut motor, check plug (an 8), on the 140mj

The CHT temp readings have always reflected a cool motor