Modern Vespa

I have 2018 primavera iget and 22000km
Recently i installed malossi power drum with new belt and new clutch.
The performance was noticeable both in acceleration and top speed it used to be around 105km after changes it reached 125 which i never seen before
So i was like why not lets take out catalyst converter from the exhaust so that would improve the airflow and power .
Since that day my fuel consumption is 3 times more lost all top speed (100kmh max)
Throttle not that responsive but low torque is ok.
I installed akrapovic + new o2 sensor just to see if those caused the problem but no performance was the same
I installed a o2 spacer with small catalyzer still nah .

I dont know what is going on with this bike i checked the clutch and the the weights all look brand new and ok.
I even installed a bolt on exhaust exit pipe to simulate back pressure but that didn't work either even though i tried with akropovic and didn't get that top speed back.

I feel like i'm going crazy please help

Check the cylinder compression. And when was the valve clearance checked last?

Spark plug is bad.

Installed a brand new one today although the previous one was in good shape
It didn't solve the issue

Never valve clearance asked the mechanic to take a look he said it will create a noise the bike sounds fine

Is the exhaust sensor wired incorrectly? Can you reverse it?

What makes you think this?

You have obviously negatively affected the air flow mechanics on a 150cc engine.

Maybe try putting the above parts back the way they were? How about that idea?

If the valve clearance is adjusted in such a way that it makes noise, it's already too late. Loss of power due to incorrect valve clearance can also occur without noise.

There's a very good reason Catalytic Converters are fitted to combustion engines so it always surprises and disappoints me when people go on the internet and openly admit they're selfish and irresponsible just in the hope they may get a fraction more power out of their scooters, especially when that extra power will not be more than 1-2 bhp at best.

it's definitely not 50 centimeters, because it's going faster than 100 km per hour

Ok, it's the 150cc. My bad.


My point remains the same.

Again, why not return it to the original condition when it was running better?

Seems rather logical to me. 🤷‍♂️

The problem is when i tried the akrapovic exhaust the problem remained that is why i'm very confused about the matter

I'm going to check the valve clearance tomorrow and update you but i don't think its that 20-25 kmh top speed drop it has to be more obvious

go backwards.
undo the modifications.

> i installed malossi power drum with new belt and new clutch.
what is a "malossi power drum"? is that a standard belt and clutch or malossi?

> I installed a o2 spacer with small catalyzer still nah

what? the O2 and catalyzer are very different things. And a "smaller catalyzer" what?

photos of the changes would help us understand what you have done

Modern engines designed as integrated units: the injection system reacts not just to the throttle, but to information from the exhaust system, coolant temperature, knock sensor (if present) and the like. Things like removing the cat without doing anything else doesn't do much, and can cause the engine to behave neurotically. Without installing a new cam, new ignition, new head and piston (possibly), I doubt you would improve performance. "Performance" exhausts deliver a far more pleasing sound, but that's about it.

It used to be fun and relatively inexpensive to hop up an IC engine. These days the cost and complexity (and the risk of causing major damage) makes buying a faster scooter (or an older one that normal humans can monkey with) a better choice, IMO.

First i changed variator to malossi multivar 2000 (three 9gram and three 13 gram weighs)
Then installed a new clutch(and clutch bell) + new belt original piaggio (both)

I noticed increased acceleration + top speed (from 105kmh to 125 kmh)

Then i wanted to increase it further so i asked local shop to take out catalyst converter out of my exhaust the bike was there for couple of days after that

The top speed went back to 105kmh
So i recon its the exhaust fault so i barrow my friend akrapovic exhaust and installed on my bike but again that didnt resolve lost top speed (after obd test i found out o2 is faulty p0032) so i installed my friend o2 sensor as well and still top speed stayed at 105kmh


So if its not the exhaust and o2 sensor what else could it be , it can't magically lose 20kmh on top speed

After all these changes i chaged air filter to malossi and installed a new spark plug those didn't help either.

My humble opinion:

It's very difficult to gain 20 km/h on these small engines with these changes; with much lighter rollers, they would be a top speed lost. All the changes you describe are as most to do a most explosive take-off, but not for top speed.

It's possible that when making the changes, the belt wasn't properly seated and was too high in the variator side maybe some of the washers are not correctly in place?), which increased the speed (but reduces the take-off). Once it was in its correct position, it's now giving the correct speed?

Always as I change the belt, I feel the scooter as being looser, less lively, but after traveling about 100-150 km that goes away, which I assume is the time for the belt to settle with the other components.

It's also possible that the 125 km/h reading was a glitch on the speedometer?

Edit: Now I read that you mix rollers 9gr and 13gr? That is not good at all! You can mix, but not with that huge difference! Maybe mix 10 with 12, and you obtain the same 11gr you have now but with a 2gr difference between rollers and not 4gr that is to much.

As Pebowles noted, you destroyed the back pressure when you destroyed the Catalytic Converter.

An Akrapovic exhaust is open to make sound., not power.

A bolt on exhaust cannot add power. It only changes the sound.

The ECU DOES NOT compensate for exhaust changes. No ECU does that.

Only fuel mapping does that.

It is PURE MYTH to think that manufacturers leave horsepower on the table. They don't.

Engineers are highly trained and technical experts. They design the balance between reliability and performance.

You changed all that. 🤷‍♂️

I am fairly certain that you now have what you have. Unless you can find an OEM exhaust again.

that's an Amateur hour move and can break the variator. Stick with all 9gr or get some 10 gram weights.

The 9 gram and 13 gram (3-3) coming from malossi pack its not something that i invented
Quick update (before i made any of this changes) something i forgot to add and just reappeared today (even before touching the exhaust ) sometimes when i'm riding i hear a hissing sound like a snake around my exhaust and right then throttle stop responding the rpm goes up but the scooter wont gain speed and just slow down
I have to play a bit with throttle until it goes away.

And about fuel injection remapping does anyone can help me how to do it?

Malossi kits comes with 2 rollers weights so you use one OR another, not combined, and if your kit use 6 rollers it comes with 6 + 6. the point is that with the huge difference 3 of them goes up very fast and 3 "long" time after, something that is not good.
As I say previously, if you are happy with the 11gr combined weight, purchase a set of 11gr rollers and put all the same, or purchase one set of 12gr and other of 10gr and combine, a small difference between both. The snake sound could be air being sucked in where it shouldn't be, or the exhaust gasket not sealing properly. Both of these things affect engine performance.

fix your existing problem first.

Fuel injection mapping requires extremely expensive equipment and a dynometer.

It is not something you can do yourself.

Apart from the dyno, what equipment are you thinking is so "extremely" expensive that is required? ie, what piece of equipment doesn't have an affordable entry level version?

Terribly sorry but I have no desire to engage you in contention of which you seem to be looking for.

Why are you trying to argue with me instead of helping the young man?

{Apologies to the anonymous Moderator}

ScottMastrocinque has been ejected from this topic for excessive know-it-allness

My set only cane in 6 weights and didn't have the extra ones , so your recommendation is to purchase another sets so the numbers are exact or close together for more balanced approach ?

Also focusing on the current problem meaning the hissing sound right?

I took it yesterday to another mechanics they told me the problem is unclear they need to spend couple of days for testing many different things as the root cause is unclear until they get to bottom of it.

I will leave it there tomorrow and update you guys as many of these mechanics are scammers over here and cant be trusted so we can discuss their findings

Thank you all for helping me out on the matter

Hey all, just a friendly reminder -- Modern Vespa is, first and foremost, a polite forum. It is not twitter or Facebook -- by default, we act with civility. We do not snipe. We are free to disagree and debate those disagreements as long as it remains friendly and civil.

I've noticed an increase in argumentative and even abusive tone from users here, and I want to be clear: anyone who behaves this way will get bounced from a thread or even bounced from the entire forum.

We now return you to your regularly scheduled programming.

The Malossi Multivar for your model comes with two sets of 6 rollers. One set is 9g and the other is 13,5g. If you installed 3x9 and 3x13,5 this is definitely your problem. I suspect that the heavier rollers gave you initially that false top speed. Mixed rollers result in non optimal operation of the variator. As suggested, I'd also go for something in between (11 or 11,5) so as not to compromise acceleration but also gain top speed…

Get your scooter back? Results?