Exhaust change on pk125s elestart VMX5T


I am French and I would be interested in a change of exhaust pipe. My PK 125 S VMX5T currently has a Sito Plus. It is equipped with a DR57 130cc kit, Dell’Orto SHBC 19/19e carburetor and the rest of the engine is original.

I would like to mount a Polini Racing art 20020510 or a SIP Racing Road art 24174000 instead. The SIP website indicates that they can be mounted on VMX5T. Do I have to make frame changes for one or the other? Will the spare tire and the battery be a problem?

Thank you.

I know this exhaust 

Sorry, but this makes no sense in your case. 

You only have a DR130 which is no high reving race barrel. 

You did not do anything else on this engine - you just clamped the barrel on the standard engine and that was it. You only have a small carburetor, no racing crankshaft, no adapted gear ratio etc.



Before you start thinking of such exhausts, I would reccomend to get the principle mechanism of a rotating-valve 2-Stroke engines back in mind.

As 2-Stroke engines are designed in a particular way, you cannot just fit every type of exhaust.
This Simonini will reduce your driving fun. 

OK, maybe you might get some extra revs in the upper rev segment (which makes the engine faster on ideal conditions), but you will loose torque in the lower revs, also on the hill, with headwinds or when your take a second person with you.


Your entry question was to gain some extra power, but the Simonini will not do this.


Also...You will have to remove such exhaust everytime when you want to change gearbox oil (which you should reglary do once a year or every 5000 km).

Also...it doesn't sound good...sounds tinny....it is just a cheap thin italian pressed metal...

the SIP Road is the better choice in your case, also  regarding optical (it doesn't look too striking) and sound aspects.

But honestly, the question is what you expect from this exhaust, with only a 19/19 carburetor...as you have not modified the crankcase inlet port (for fitting a 24 mm diameter carb), and for sure you did not adapt the transfer ports from crankcase into the cylinder.
All these measurements are intended to set free more power and reaching higher rev levels.

But the DR 130 is more a tractor like cylinder, which is not meant to be operated at high revs regulary.

Hi !

"If you are not dependend on the electrical starter, it is possible then to rebuild the electrical system to work without a batterie, as all PKs, which are not eqipped wit the „e-start“ option, do.

My PK has an ETS exhaust, and no battery. Works perfect."

Have you do yourself the electrical rebuild ? How can I make this ?

It will be ok for me to exchange spare wheel by repair spray but can we use it on tire with tube ?

Otherwise, i’ve found this right side exhaust, Maybe less esthetical but more simple to mount.


Guten Abend,

Thank you for your reply.
The advantage of the exhaust change is to gain a few horses, a little pleasure. I know it would take more than an exhaust to get a herd of horses. My „sito plus“ is very tired, so take one more effective. My main concern remains the assembly, I have the spare wheel with the battery in the middle. The battery is used for the starter, the indicators, the brake light … I cannot exclude it.

That's an important supplemetary information, thanks.

If you want to keep the battery and the spare wheel, unfortunately, both, the SIP Road and the Polini exhaust are out of the question, as their design does not allow the space for batterie and spare wheel.

Also be aware of the fact that it would not be a good idea to remove the sparewheel, but place the battery a little bit higher - the hot exhaust will heat up the battery.

But, another question yet, please excuse me but I would like to be sure:
Do you really have the SITO PLUS or is it the "standard" SITO for the PK80-125ccm?

This is the SITO PLUS (with alternative Pipe geometry, compared to the standard version):

I would say, to buy a new SITO plus to replace the worn out old one would seem to be a lean choice.

With the DR130 only, you would not gain remarkable more output with any race exhaust...as it is comparable to an ETS 125ccm setup...maybe 0.7 to 1.2 horses could be set free...the limiting factor is the small carb and the crankshaft, and the lack of reworking the engine's inlet port and transfer ports plus some minor fine tuning.

By the way, I also own a PK 125, and I have 2 engines on the shelf, one of them similiar to yours, with a DR 130...

With any other left sided race exhaust it is always necessary to remove the exhaust, if you need to get access to the rear wheel.

If you are not dependend on the electrical starter, it is possible then to rebuild the electrical system to work without a batterie, as all PKs, which are not eqipped wit the "e-start" option, do.

My PK has an ETS exhaust, and no battery. Works perfect. No need to think of the battery charge. OK, I don't have a spare wheel, but when I'm on tour I carry a can of tyre emergency repair spray with me.

Honestly, after 33 years, I did not experience too many punctured tubes myself. Not more than a handful. But I have to confess that I change tyres regulary to comply with the legal situation (but mainly to my own safety), and every time when I do this it is compulsory for me to also change the tube.

I also take care that I don't damage tubes whilst assembly. So ... no sloppy assembly with the valve sitting a little displaced...also taking care that I don't squeeze the tube between the rim halves...after all of the tubes I've changed on other Vespas than my own ones I have to accept that in most of the cases they where not damaged by something coming from the outside...


The problem with the larger diameter of the hose and the hindering of the passage of the tire ...well, I don't see a particular explanation from my desk here...but it might be a question of the tyre type and its profile.

Thks for reply !

Yes, it’s a ‚sito plus‘. Besides, I’m having trouble removing the rear wheel. The hose has a larger diameter on one part and hinders the passage of the tire … for the punctured wheel it is not annoying but for the inflated spare wheel it does not pass. in short …

So if I understand you correctly the spare wheel must be removed or moved and the battery must be placed elsewhere or higher; That’s what I feared.

I do not want to put a „Sito plus“ again, I bought it new on the site in 2008 to replace a tired „original“ when I bought my pk.


Thx for reply.

Thank you for all these details, I will think about it.

Best regards,