Modern Vespa

Hi,scootermarc69
i have studied your carb mod and your exhaust project before.
The Keihin Pwk 28 when is used to 4strokes engines gives sometimes problems at low rpm,PE28 runs better.The stumble may dissapear if you lower the clip of the needle one or two positions to make the mixture rich and set the mixture screw then at the turns that gives the highest rpm with the throttle closed.
If nothing good happens,try a thinner needle to make the mixture rich enough.

The second reason i don't use extension tube at the carb,is that i am afraid it may affects power at high rpm.

About the exhaust my friend,stay tuned.
I am working on a Superflow flow bench now,we have to measure head porting,intake extension tubes,exhaust flow,etc.
Numbers are better than butt dynos.

Last edited by dynagrego on Wed, 24 Oct 2012 14:33:13 +0000; edited 1 time

Thank you for the answers, I bet you can tell I am a rookie when it comes to these things, and because of that I have some other questions..
You lost me at the valve job... So you replaced the stock 150cc intake and exhaust valves with bigger ones. Wait what? From which scooter model? From what cylinder head?
Afterwards you show a picture with the old cylinder head and the 150cc piston on the left and "specials" on the right. What are the specials? What type of cylinder head is the new one with the bigger valves, and I suppose the cylinder is the Malossi 190, not the Liberty 200, right?
If I will use the Liberty 200 cylinder + assy with the original LX150cc cylinder head, will it work? If yes, which cylinder head packing (gasket) should I use? The bigger one, that suits the Liberty 200 assy? Or the original that suits the LX150 cylinder head?

They are different:

Liberty200 http://www.easyparts.nl/showarticles_info/0015843204/0-968-1-m420-m106-m6274-m2330-s2162-d38485/2162/Head_Cylinder_Packing.html

LX150
http://www.easyparts.nl/showarticles_info/001582682R/0-968-1-m425-m1557-m1560-m1566-s12563-d110029/1566/Packing.html


Now about your last picture, which I believe is the Pwk28 carb setup on scootermarc69's Vespa LX150. I am even more lost... The secondary air hose is disconnected from the intake manifold and capped. Ok.. Why? The fuel hose from the intake manifold goes to a T which feeds back to the top of the carburator.. Why? Is that how is supposed to work? Because is not vacuum like the stock one? So the secondary air system on the LX150 becomes obsolete?
On your PE28 setup on the ET150 engine, where is that grey hose going? There's an evap hose on the side which you clamped, I got that, but the two black hoses going in the carb, which one is which? Both from the fuel pump?

Thank you again, and bare with me here, I'm a bit slow..


Pixel

The intake length on the piaggio engines is way to short to get any good and useful resonance. Even on the 250 we had to extend the intake by much more than what it would take to get the carb positioned here.

GTS Tuned Intake

If anything I'd think the longer intake would help.

1.I use Ferrea valves.I passed them from the lathe to give them the length and shape of the original and machined the valve seats to match the bigger valves.
Cylinder head is stock from a liberty 125,it's the same as yours(lx 150).
The only difference from et4's head is a small port above the exhaust for the exhaust gas cleaning system that i have tapped.
All air cooled Piaggio leader engines(125-150-200) use the same cylinder head so you are okay.

2.You have to buy cylinder head gasket for liberty 200 for use with the Liberty 200 cylinder kit.


3.


Last edited by dynagrego on Thu, 25 Oct 2012 05:30:28 +0000; edited 1 time

That's very interesting because theory says that short intake runs good at full engine load, and long intake works well at lower load.
Anyway i''ll try several tips on the flow bench and maybe later on a dynamometer.
Of course,the best would be a Variable length intake manifold,not exactly a piece of cake for me.


Honda DOHC i-VTEC, dual-passage intake manifold.

it's true that the higher the RPM the shorter the intake needs to be but the stock length would be ideal at like 17000 RPM or something crazy like that. We did a long extension to get it effective at a max of 8500. Would need to be even longer to work at lower rpm.

Gday guys.
Good to see some of you are having fun with scoots still. Hotrodding a scoot can be MORE fun than the usual 200+Hp suspects sometimes.
Better grin factor when you notice the changes.

Dynagrego, thank you very much for your write-up on the AC Leader, excellent help and pics all round.

The chart below is an intake length tuning chart, based on RPM. The 2nd harmonics are the strongest, but more usually the 3rd harmonics are used due to packaging reasons, and the 4th still has a noticeable effect over no tuning at all.

Hope this will help in your future tuning quests.
I've found over the years that getting the intake tuning right, even just using the 3rd harmonic, and ALSO getting the exhaust system tuned to match, can be worth in excess of 10% extra over already good set-ups.

Thanks for the Leader info.

Cool chart!

Also the exhaust is often tuned to give a boost in between the harmonics of the intake to smooth out the power. This can be useful on a CVT as a dip in power can sometimes be hard to push through.

Great info MODNROD !
1.But what do you mean with "intake length"?The black rubber carburetor intake manifold or the distance from the valve stem to the carburetor's slide or something else that includes the air filter?

2.What is the right intake length according to this chart for a leader engine that is running steadily at about 7500-8000 rpm?12''=30,5cm?
I think that this will affect throttle responce too much.

Normally the intake length is measured from the face of the valve to the first widening section (ie the bell of the carb or throttle body). This is because the sound waves reflect when the cross section changes.

In the stock setup with the carb and then the snorkel you end up with two sets of sound waves reflecting around. I'm sure that piaggio models this and dials it in just so to hit power/economy targets but the software to do it is ~$60K.

For the bell we made for the GTS we had it fit smoothly into the throttle body so that there was no crosssection change at that point. this extended the tuned length all the way out the end of the bell.

The intake "tuned" length is measured from the back of the valve to the end of the trumpet. Although there is a throttle blade somewhere along the intake tract, and yes although it does have a slight effect, when the engine is WOT the tuning length goes to the first either major obstruction, or the first open end (end of bellmouth).
When cruising at part throttle, the intake length has very little effect on engine output compared to other factors like reduced cylinder fill and timing.

On a dragbike, I would pick the intake length that corresponds with my highest shift point, thereby getting maximum benefit from the shift point down to the drop-rev point in the next gear.

For a scoot, I would pick the top rev range chosen in high-speed operation (eg. 8500 seems to be where most of these scoot motors rev to at the top), then line up that rev point with the top of the selected intake length.

8500 RPM would correspond to 2nd Harmonic length of 16.9" with an average of 10% boost to the curve (that's a max theoretical boost value), 3rd Harmonic length of 12.1" with a boost of 7%, 4th Harmonic length of approx (off the chart) 8" with a 4% boost, etc.

If you decide to alter cam timing and ports/carbs/valves to get 10000rpm for extra power, then pick the 10000rpm line to find your intake length.

And yes, it is sometimes possible to set exhaust length and diameter/volume to "fill in" the dip between 2nd harmonic and 3rd harmonic to get more average power over that range, better than more peak power. 17" intake length at the 2nd harmonic tuned for 7500-8500rpm will also give a 3rd harmonic boost from 5000-6000, so you could set your exhaust tuning to 6750 to give a total boost over the 5000-8500 range for the best average power.........theoretically!

The variation in intake diameter does affect the tuning, but an open bell mouth has vastly more tuning effect than the "steps" in the path.

An excellent tool (and great for learning) is a program called Pipemax.
In practise it actually works quite well, and generally as predicted.

I'm really curious about it,i'm going measure the factory "intake length".

The main problem to see 10000rpm or more is the piaggio ignition's limiter as you see at this screenshot from the manual.

I am waiting answer for prices from this company.
http://www.hpi.be/applist.htm
information
This CDI bypasses the original immobiliser system and is a direct replacements for the original part.
Our parts are direct replacements for the OEM CDI. Each CDI is factory tuned and tested.
CDI's come with all the required connectors and wiring, making replacement of your standard CDI as easy as possible.
The Digital CDI-unit is developed for optimal racing performance. Made from state of the art technology and based on 30 years of experience in motorcycle-electronics. Your engine will start easier and will run at the highest possible performance.
The timing curve has been developed on a dyno and tested under race conditions.
All units deliver massive gains on the track, where you'll really notice the difference.
Possible options are: 2 curves, powerjet, throttle position (6 curves), and can be programmed with your own curves using our TuneBox software.

I think (though not sure) that the CDI from the GT, or the malossi CDI for the GT, can be used on the ET/LX.

When I was about done modifying the GT harness to fit my LX I realized there are not that many differences. The GT CDI also has a pulse for the turn signals but you don't have to use it so you may not need any modifications.

With your cam and valve work is the power still climbing at 9000?

I haven't finished with the head porting yet,maybe next week i''ll be ready.
But big piston,valves,carburetor and camshaft are enough to hit already the limiter on a flat road.

I don't worry about piston,connecting rod or crankshaft bearings if i raise the limiter.At 10000 rpm also,the linear velocity of the Malossi piston will be only 16,2m/sec,so i am safe enough.

But i worry about the strength of the transmittion system,especially the belt,variator and drive pulley.If something goes wrong there,it will be a disaster.

The transmission can take the 20hp that the GT puts out and then some, so don't worry about that. The crank is basically the same as the GT as well so no worry there either.

The valve train will likely be the limiting factor, so interested to see how it does.

I mentioned the 10000rpm thing coz I figure with your head, cam and carb, that would be a more realistic peak power mark than 8500. I spose you'd just have to test a few things, it's pretty easy to alter stack length with bits of tubing or rubber/silicon hose and then time the thing off accelerating from 50kph to 100kph.
For me I'm in the process of looking for a get-to-work ride. For me that involves 200km return trip over bumpy bitumen rolling hills with 20km of gravel (I work 4 on, 4 off) with clothes and food for 4 days. My TT Supra doesn't like the bumps much (go figure? ), my Vmax is downright scary on the gravel, and my beloved little VW Bug is in pieces waiting some lovin!
Maybe it's just a mid-life crisis, but a friend offered me his 2009 Aprilia Sportcity One (125 AC Leader) coz he knows I've had a few scoots over the years and love them, but since at the moment the Supra needs work so I'm sitting on 80-90kph to work, the idea of 90kph for over an hour dodging road trains, although interesting and probably fun (it IS a scoot after all!), isn't appealing.
Thanks to your write-up I now know I can have a 200cc ride that should do 100-110 all day long, and the best thing is the air-cooling! WOO!HOO!
Yep, definately mid-life crisis! Get rid of all the water-cooled crap, back to simple basics, an air-cooled scoot, an air-cooled hotrod VW, an air-cooled drag Kwak for the track, not a radiator in sight!
The little scoot is an awful lime-yellow colour, but I might give him a ring later I reckon. I'm thinking 200cc, ported head with stock cam, Polini upgear, 28mm flatslide.........oh yeah, and flat black with flames! HAHA!
Thanks for your help Dyno and Oops, much appreciated.

Sorry guys,but 467eur~600$ are too much for a scooter's ignition.

OK.
This is NOT a plug-and-play, and I haven't contacted them to determine suitability for these machines, and I doubt it would interface with the stock immobiliser etc, but these guys do a lot of fairly adaptable set-ups, and a quick chat to them to explain your requirements may lead to a suitable way of optimising ignition and/or injection.
http://www.ignitech.cz/english/aindex.htm
http://www.ignitech.cz/english/aindex.htm
I think if they realise how many of these Piaggio units are around, and if there are enough customers for them to develop a specific product to suit different options (eg, Vespa 250GTS, Berverly 300, X-9 500, X-Evo 400 just with wiring and software differences to suit, but the same basic hardware), they may be willing to look into it........
Apart from that, I wouldn't pay $600 for a TCI either. OUCH!

These guys have a CVK throtle body and programable ignition. http://ecotrons.com/Small_Engine_EFI_PNP_kit.html

Theoretically i can use any CDI ignition from a single cylinder carbureted motorcycle,piaggio or japan made.
If the pick up sensor doesn't match,i may bolt the sensor from the new cdi.

But practically,there are some problems to solve:
1.there will be no immobiliser. I don't care cause i never trusted it.
2.I have something to do with turn signals,our ignition controlls them now.I''ll need a turn signals relay.
3.The most important is to find an ignition with no rev limiter but with advance curve that matches to the needs of the Leader engine.
Here are the advance curves of Leader 125 and Leader 150 engines.
Ignition advance of the 150.
10° at 2000 rpm - 26° at 6000 rpm

Ignition advance of the 125.
It seems more angry,the big 150cc piston may put under bigger stress the crankshaft bearings and may this is a tip for safety.
But i would like to try it,because i haven't heard for troubles from the 125 owners that bolted a big cc kit before.
15° at 2000 rpm - 28° at 6000 rpm



I see that there are many differences of the values,like the two engines are completely different,not only some more millimiters of piston's diameter.

Last edited by dynagrego on Wed, 31 Oct 2012 07:07:39 +0000; edited 1 time

I just had a quick look, what a great product! Thanks for the link, I could have used that for friends bikes many times over.

If you are able to adjust the closed loop control AFR for steady part-throttle cruise conditions, it would be ideal. As an aside, some air-cooled motors get hot while cruising on 14.7:1. It's the ideal AFR to allow operation of most modern cat converters, but overheating on air-cooled engines in these conditions (that aren't using a cat converter) can often be reduced or eliminated by running an AFR of over 16:1, as well as gaining better economy over the usual method of dropping cruise AFR to 13:1 to cool them down. Lean or stoich cruise can sometimes cause overheating, but VERY lean cruise does the opposite.

Dyno, I think the 125 advance curve would suit your motor better. The extra timing advance at idle would suit your bigger-duration cam specs, and the extra 2deg at high revs shouldn't overheat it. If it does, try a spark plug one or 1/2 range colder and you should be good to go.

A quick stoooopid question please Dyno.
Do you know how thick the standard Piaggio cast iron (are they? or alloy?) cylinder liners are, the wall thickness? Do you know if the 150cc has the same barrel as the 125 just bored out, or is the 150 barrel thicker?
Thanks in advance.

I don't know about the 125.
But i know that the 150 can accept maximum 1-2mm thicker sleeve.

Unpacking and installing the PM tuning clutch bell.

I bought the clutch bell direct from PM Tuning.
http://www.psntuning.co.uk/scooter_parts.php?prt_id=559

It weights only 750 gr when polini weights 950gr and factory 1100gr.
It is a very good quality product and it's about the same with that from the world record's scooter(11.90 sec 0-400m,169km exit speed).
I payed with paypal and the shipping was fast..

It's made from gold!



new next to old


back side


factory bell is taller!


They give you a new spacer.I don't know why,it is the same with the old one.



it's a pitty that it's hidden behind the trans cover.


I have read a report for a bended bell like this,but i''ll use it on the road,not on the track.I hope it last.

not expensive, no limiter, same plugs, designed for the LC 4V motor that spins to 10000.

for harness without immobilizer
http://www.sip-scootershop.com/en/products/cdi+ignition+unit+malossi+_m5512524

for harness with immobilizer (there is no immobilizer in it but it works with the harness)
http://www.sip-scootershop.com/en/products/cdi+ignition+unit+malossi+_m5512341

Very interesting!
Can we find the advance curve?

What do we do with the turn signals?
Does it support them?

It's designed for the GT so, yes it has the turn signal circuit in it.

I'd suspect the ignition curve would be about the same as the GT200.

Removing the decompression device for faster revving.




After the light clutch bell swap,here is another tip for faster revving and simpliciity.
I removed all the decompression device from the camshaft.
Centrifugal weight,decompression bell,spring,etc gave their place to the 2 camshaft shims from liberty 125 head as you see at the picture.
The decompression mechanism is for the kickstarter version of leader engine,models with and without it have exactly the same strong electric starter.
I didn't notice any change,scooter starts easy as usual when i press the button.

Does it work?
It isn't exactly like a turbo or nitrous mod but we are speaking about a stage2 tuning,so it is nessesary to lighten some moving parts.

From the valve stem to the carb opening=157mm~6,18"
From the valve stem to the slide=4"
Not so good according to your chart.

That's not unexpected, it's more about packaging in a tight space than optimising runner length. If the manufacturer was into at least attempting to optimise runner length and volume regardless of the effect on storage or tank size (if you get the chance, have a look inside the airbox of a Ducati 4V made in the last 5 or 6 years........), then in the case of scooters the carb might be downdraft with the air filter right at the front of the seat.
Anyway, if you could extend the inlet tubing from a pod or airbox entry to the carb inlet......
Tuned for 10000------an extra 8".
tuned for 9000---------an extra 10".
tuned for 8500---------an extra 11".
This is for the 2nd harmonic, the strongest tuning pulse.

Treasure hunting:The Myth of the Hidden Horses.
Porting the head


The myth says that many horses hide behind the small valves and ports of Leader's cylinder head.
There is a rule that says the intake valve must be 45-50% of cylinder's diameter if we want to have great power.Malossi cylinder is 70mm so we must have at least 31,5mm diameter of the intake valve.But factory valve is only 27mm and there isn't much space to put bigger than 28mm as i did,without serious modicifications of the head.
The exhaust valve is also very small for a 200cc engine at 21mm and the best i did was a 22 mm valve.
A 4valve head would be the solution but i love my simple,air cooled,2valve motor.

So,the Leader is an engine made for torque,not for power but as we saw at the Superflow flow bench the Myth of the Hidden Horses is true,there are big gains if you port the head.

On the left of the picture the factory intake.On the right,the ported one.

Last edited by dynagrego on Sat, 03 Nov 2012 19:32:02 +0000; edited 1 time

Compare porting behind valve seats,factory on the left.


Ported exhaust side.Now it matches with the exhaust tube.



We made a small fin,where the red arrow points,for better flow.


Matcing carburetor and rubber intake behind it,there must be no steps.


Funny,intake valve has the same diameter as carburetor,at 28mm.



Last edited by dynagrego on Sat, 03 Nov 2012 19:34:38 +0000; edited 1 time

Gday again Dyna.
I'm curious about the head flow, and the valves you used. Would it be possible to use valves of the same stem diameter and a length you could work with that would fit? For example, if the valve length standard is 100mm and stem of 6mm, it may be possible to substitute valves out of a Kawasaki Z650 (intake valve 31mm, 6mm stem, 102mm length), just as an example. Do you know of any off-the-shelf valves from something that would come close, or are your cut-down Pro-Flows easy to get in there?
As an aside, the 1970's Z650 Kawasaki has bore of 66mm, intake valve of 33mm (from memory, I think?), and standard makes 70HP @ 8500rpm. I had one years ago that with standard bore/valves/carbs of 34mm CV, made over 85rwhp @ 10000, just through porting and a mild cam.
On this Leader single at 190cc, with porting to suit and attention to squish for good burn, I don't see why you couldn't get 18-20HP @under-10000rpm out of it.
Oh yeah, I like the port shape, nice blending around the valve guide support! 8) How much room is there in the walls?

EDIT: Oh yeah, something else, sorry!
Your valve lift/diameter ratio is about 0.25, do you think the port and chamber shape would lend itself to using 30deg seats instead of the more usual 45deg for the sealing cut?

If someone wants bigger valves than mine,has to fill the combustion chamber first and recreate it from the beginning.

Yes,there is much material to grind but this is the reason i used a flow bench,i didn't want to kill the power at low rpm.

We noticed a serious problem when we put the head on the flow bench:The intake flow at 1mm lift was about zero because of improper cutting of the valve seat for installing the bigger valve!!
It was making something like tube effect so i cut again the valve seat at a much better machine.

Cutting valve seat from the beginning


Testing for leakage using vacuum tool.

I had in mind the Kawasaki GPZ too!
Great power with only 8 valves. I don't think i can make more things at this head.

Today i put the engine back on the frame and i rode the scooter around the city.
Idle is good and throttle response is better than stock because of the type of the carburetor.It revs fast up to the limiter,much faster than before and it begs for a free exhaust.Now i have the original silencer because the crappy sito plus doesn't match.
Power is more than the frame and 10'' wheels can handle,i wish you could have a ride.
Mileage is 5-5,5lt/100km with fast driving.

Performance at high speeds is something that i expected.
The unexpected is the wheelie at the throttle opening after the traffic light turns green.
I think that this has nothing to do with the head's porting.Maybe the light clutch bell in relation of fixing the problem of the intake valve seat at 1mm lift are the reason for the traffic light wheelie.
Remember that wheelies are more difficult for my engine because of the much taller transmittion(polini upgear kit).
I also have to say that i wanted reliability first from all my modifications.The camshaft lobes are designed to put under small stress the rocking levers-valves-seats system and i didn't cut a lot from the valve guide's length when i ported the head.It's not a stage3 drag bike,it's a scooter for every day use with much more fun.
Exhaust,advance curve and rpm limiter are the next target for me.

oopsclunkthud,i have a terrible need of trying the malossi cdi.

This Excel worksheet from the flow bench is the inlet flow comparison between my cylinder head with bigger valves before("standard") and after("modified") the porting.
Flow is measured by CFM(Cubic feet per minute) and you can see clearly now,that at 1mm lift the "standard" gave only 2cfm of flow!That happens because the combustion chamber gave his shadow over the bigger valves.
After modifying the chamber,the flow climbed to 6,6cfm.

A cylinder head with normal valves should have a very small difference before and after porting up to 2,5mm lift.




If i could jam a little more the outer lips of the inlet,then there would be a serious increase of flow over 5mm lift.
But i have already jam too much the walls of the black rubber intake and i didn't find something bigger aftermarket.

Flow results,exhaust side.

Got a Piaggo part number for these?

They should be Item Nr 8 and 9 on the drawing...
http://www.piaggiospares.co.uk/spares/epc2.asp?modelID=11820&PageiD=43&m=LIBERTY+125+4T+%28EURO+3%29+MOC-ELLE+M671M+2009-2011+rocking+levers+support+unit+&uID=0

codes:
8= 830446
9=830447

But mine are much bigger,maybe the drawing is faulty.
All aircooled leader engines without kickstarter must have them,they don't need decompression system.So you can search between Piaggio Liberty and Fly 125-150,the models without kickstarter hole on the trans cover.