Modern Vespa

So i have had my PK125XL for a while now and i have found myself on the highway a lot more often than i imagined when i bought it.

It is quite a struggle to keep up at 80km/h up a hill without the slipstream of a semitruck and "passing power" is a solid "no"

The "propper" solution would probably be to go get a 200cc Vespa like a PX200 buuuuut i quite like my PK and its not that far off from a performance level id be more comfortable with.

I dont want to do anything that can't be undone and i also dont want to end up with a scoot that cant be used for bopping around town at 20km/h so pretty mild mods. Budget is also pretty mild, maybe €200 or so?

Right now i am looking at the MALOSSI "Power Exhaust" Banane: https://www.sip-scootershop.com/en/product/racing-exhaust-malossi-power-exhaust-banane_M3219292?usrc=Racing%20Exhaust%2080-125cc,%2051mm-%3E

And the POLINI Banane Sport: https://www.sip-scootershop.com/en/product/racing-exhaust-polini-banane-sport_20020510?usrc=Racing%20Exhaust%2080-125cc,%2051mm-%3E

Are these good picks or should i be looking elsewhere? Do i need any supporting mods? Will the VMX6T cases simply shatter under the strain of a little extra power?

Get the newer Polini 'Banana' definitely better than the old one…

https://www.sip-scootershop.com/en/product/racing-exhaust-polini-original_20020540

what are the highway speed limits you want to run at?

one of the best bang for the buck to run around 50-55 mph is short 4th on the primavera gearbox. not sure if the later pk xl gearbox had same ratios as the primavera, but the primavera 4th is way too long, leaving you out of the power band in 4th even with simple setups like DR130 + polini banana.

Good point, seems like a solid choice

Speed limit is 80km/h at most, trafic rarely moves over 90km/h during the hours I commute. Not sure about the gear ratios but I feel like I am past the power peak at 80km/h because it pulls pretty well to about 70-75km/h, on a downhill I can get it to the theoretical max of 95km/h

your speed needs aren't that nuts at all

dropping a 135 kit of some sort on there and getting a short 4th tree you'll easily get there.

Johnny mule hit it right on the head. kit, banana pipe, short fourth or long 3rd. straight drop on, just re-jet the stock carb and you're in business.

if you keep it mellow, you can just upgrade the stock clutch with good plates and springs. you don't need to get some high dollar aftermarket piece.

Before spending on anything, you could try a little O tuning. Take off the cylinder head, skim down at least 1.5mm. Put a 1mm packer under the cylinder. Up the ignition timing a little. Up the main and pilot jets to suit. Should be good for a few more km/h.

I also have a PK125XL, except it isn't stock anymore. But back when it was, i installed a DRT short 4th gear in it. It was worth the work to get it installed. It gave me a little boost in power for the hills and headwinds. It was still good for just over 55mph on a flat, but still not a lot of torque. I still had the stock muffler though.

FYI, the VMX6T case is the bestest of any smallframe! You won't have any problems with it.

Oldschool, i like it Reminds me of the stories my oncle used to tell me about how he snuck his cylinderheads into woodworking class and use the powertools to do stuff like that when the teacher was looking elsewhere

Too bad the mill i have access too is out of order right now as it is getting a VFD installed... If anything were too go wrong my vespa would be out of order for quite a while and a large buck so i think ill look elsewhere for now.

What i am getting is at least that it seem just doing an exhaust wont cut it?

Old school but still works, all free and virtually fool proof. Getting a big bore kit would seem easier but this begins a whole world of modification and damage cycle for the less experienced.

The head can be skimmed on a belt sander and smoothed on glass. No fancy tools required.

I used to do the same at school with my 50 special parts. Was decking cylinders at 16.

I just got the same bike and was thinking about just what you are looking for. I like the newer Polini banana that SaFiS suggested, and Jack's plan for the stock top end.

But I also like SHB 20L carbs and have 2 on older stockish 125 smallies. I like the integral bellmouth and simpler clamping, and they use the same jets as other SHBs.

SaFiS, I think they came stock on only some later version PK125, maybe ETS or Elestart ? And with the Polini pipe and Jack's top end mods, do you think this would be a good fit?

Right now i am leaning towards buying the new Polini banana and adjusting jetting as needed and seeing what that gets me.

After that ill either get a kit for higher capacity like a 135 kit or if the mill is working again maybe skim the head if i am still not satisfied.

Installing a cylinder kit is a bit risky with my current workshop situation as i cant keep my Vespa in the shop overnight so if i cant ride it home i have a problem It is a lot less work to just swap an exhaust

Right, about to order the new polini banana, just have a question about jetting.

I only have one jet kit, sizes 100-122, is this the range doing an exhaust swap would land me in or should I get the 75-98 kit as well?

Right now I am running a size 80 main and a 60 idle with everything stock. I'd expect to jet up maybe two sizes but I can't find much good info and I don't really have any experience with 2t tuning beyond cutting the restrictor out of my first moped 😂

Ended up with the Malossi Power Exhaust Banane instead of the Polini.

Took >10h to install...

The holes for the manifold were not drilled in the right places, the exhaust gasket was wrong but some time with a drill and dremmel fixed both of those. Not too happy about having to remove the exhaust to get the tire off now though. There is a lot of space it could have swung out behind the panel as the spare wheel won't fit with it anyway but instead it hugs the wheel so tight I can't even get a finger in there...

Ended up with an 88 main jet, started with a 90 but it just would not rev when opening the throttle. Plug came out black as night and soaked in gas so stepped it down to an 88 and it ran and revved like expected. Still stumbles a bit on acceleration and at low speeds so I think it is still too rich but the plug looks alright and better to start out rich.

Might put an 86 in there at a later date but I did this tuning at about midnight yesterday so good enough was good enough

Power seems good. I don't feel like I lost any low end and the top end is phat going from 50 to 70 km/h in third feels amazing, before the power would really taper off but now it pulls great all the way!

Have yet to test this on the hill I specifically wanted the power for but it feels solid so far! Might need to get a muffler though, it is a tad loud for bopping around town 😅

The ones that I rode managed too hit at least 95km/h but sometimes 100km/h(on the speedometer). What I did noticed is that the gearing seemed short in my opinion but they were peppy.

What I think I would do in your case would be putting a cylinder kit, a nice exhaust and upping the gearing if needed. I am not sure you can fit a P200 engine on a narrow chasi PK. Are you hitting 80km/.h on the speedometer or GPS?

All numbers are speedo, I don't have a nice enough GPS for a reliable number.

As it was I could go a bit over 90 on the flat or downhill, just a specific uphill I go up almost every day that I was struggling to get up at 80.

Now with the exhaust, the main thing I have noticed is that it revs higher than before. Before it was running out of breath at 70 in third, now it keeps pulling past that.

I have still not had the opportunity to ride that hill yet, not sure when I will actually, maybe next week unless I go out of my way to ride it.

This is why I want to suggest new Polini Original. But I saw your thread too late.
Polini was absolutely perfect to mount and works also very nice as for me.

you might worry about the temperature of your tire....

Couldn't find much of anything about either exhaust so bought the Malossi as it was way newer and a bit more affordable.

Seems like I definitely bought the wrong exhaust

Malossi is not new. The Polini Original we suggested is the newest of them all…

Welcome to the work of tuning, mistakes will be made…

After some riding about now with highway and city stuff here is a plug comparison.

This is NOT a plug chop.

Just for clarity, again this IS NOT A PLUG CHOP.

This is just the smushed together average of the last few days of riding.

I would say it is on the lean/hot side?

Jets are 88 main and 60 idle.

The brand new and current plugs are NGK B7ES and the one I was running with the old exhaust was an NGK BPR7ES. I also ran the current plug with the old exhaust and it seemed happier with the B7ES than the BPR7ES.

Plug gaps are all 0.55-0.6mm.

Not sure what to do about this though, if I go to the next size up in main jet it fourstrokes with more than 1/6th throttle opening and it already has the largest idle I can find available.

Still bogs on acceleration from a red light and seems to fourstrokes or stumble at 40-50 km/h which to me feels like it is too rich on the main still?

Maybe what I need to do is swap to an aftermarket air filter and up the main to a 90?

Ok well....
Lemme just....

60 idle jet seems too big. There is 52 on my SIP/VMC 125cc cylinder, racing crank shaft, SHBC 20L and Polini Original.
Before you buy new fancy air filter you can upgrade your original one like I'm done here.

Or do bit smaller holes as Malossi recommend for their cylinders.

Reeeeeeeeeeeeally wishing I had read through the entire Snowball thread before buying anything now

The Polini Original looks fantastic, the fit seems awesome... Maybe I'll just buy that and concider this exhaust "learning money"

If I get some time I will swap the idle jet for a smaller size, and I will probably have to increase the main to compensate. Will definitely drill my air filter like you have whenever I get some time for tuning.

Got a busy week ahead and then I'm leaving town for a month so nothing will probably happen for a while with this

Feel free to ask any questions in Snowball thread or in PM. I will glad to help you.

the Nyloc wheel nuts are not fitted correctly the nyloc is not touching metal.(top Photo)

Sharp eye and great tip!
bananasplit_00 don't use nylocks on the wheel studs. Go with standard spring washer and nut.

Yep, well aware just have not got the hardware to fix it right now. Previous owner has used nylock everywhere instead of spring washers and normal nuts. It was even on the exhaust....

Ah uploaded the picture of before I tightened all the nuts. Good catch, they were all correctly installed before I ever rode away

So the PK died on my way home today. Just shut off completely at the crest of an uphill. Wouldn't start and I had no tools.

This was after a 30min highway ride at 60-90 km/h and a similar trip earlier in the day.

Anyway got picked up by a very nice man named Alex with a big van and we packed the Vespa in the back and I got a ride to my garage.

Pulled the plug and it is as black as night. Think my jetting might be a bit rich rather than lean as I thought.

Going to pull the carb and change the idle to the 50 I've got and see what that does on a quick ride.

Found the issue and can confidently start that I have encountered the strangest thing in my wrenching career...

The main jet fell out..?

Changed out the jetting today as I got a few hours free unexpectedly.

Now running a 50 idle jet and 90 main. It ran pretty bad when I first put that combo in at high throttle and the plug was pretty black when I pulled it so I did as suggested and drilled the air filter box

That one change made it run amazing right away, much better than it ran even with the old exhaust

Great at any throttle position at any speed, expect launch. It sometimes bogs pretty bad on launch if you don't spin it up and slip the clutch enough.

Think I might go up to a 92 main as the plug looks a little pale to me but that will have to wait, just locked the bike away as I will be gone for the next month.

What plug are you running there? Looks like the long reach version used in P200 & LML motors that have thicker heads. Small frame and large frame 125/150 motors usually use the short reach plugs.

I'm running NGK B7ES as PK XL uses long reach, see: PK125XL Elestart spark plug? (Post 2649390)

It's pretty confusing honestly

Here is for PK 125 S - not XL. Better to check what you really need.

So with new jetting that feels great the Vespa is now quick but slow.

I've lost almost 20km/h top speed up hills because fourth is practically useless for anything not flat or downhill.

Acceleration is great, as long as you avoid bogging on launch it shoots off and pulls great until you get to the top of third at about 70km/h.

Not sure what to do about this, maybe I just bought the wrong pipe or maybe I really do need that short 4th. I am a bit afraid to loose top speed and make the fuel efficiency even worse but I've got to do something about this for sure...

If i can interject, i have the PK75XL, the motovespa cousin of your 125XL. As standard mine uses a 20L carb. Book speed for the 75 is 80kmh and for the 125 90km. I could hit over 80kmh with a sito plus, but lousy on hills and wind so I bought the often overlooked BGM box pipe for small-frames; its relatively inexpensive and gives you complete access to rear wheel. I lose about 2KMH top end, but the pulling up hills and maintaining speed into wind is far better as i have far more torque. Im not sure of the original jetting for the 125 xl but having a 90 jet seems awfully high to me. The XL uses the same carb as the ETS; doesnt the xl also have the same engine? Standard factory is 10569.1 Slide
76 Main jet
50 Idle jet
60 Starter jet
Float 6122.2 3.5 grams . My scoot in pic, BGM box pipe.

As for the plug, yes it should be using a 19mm long reach, as confirmed in the manual pic attached. Malc

I'll check the plug once I can swing by the workshop, hopefully tomorrow, should tell me if it is too rich still. Looked good on a short test ride but maybe I could go down a size or so. Just being careful not to damage the motor as this is my daily commuter.

I think I might just have the wrong pipe for my application. That box pipe seems like a better choice based on your experience. I don't need much top speed, I just need to get up hills at 80km/h so I don't get froggered by a truck or SUV