Modern Vespa

Hi I have a Vespa PX125 2016 70th anniversary edition and I am thinking of buying a Zeus CDI. Apart from a Sip 2 racing exhaust it is completely stock. My question is I know that I will have to upjet the carburetor but could somebody please help me out on the size of the main jet and is it a push on jet or a screw in? Any advice would be much appreciated. Would I have to upjet the other jets too? Thanks for taking the time to read this and I hope someone could help me out. Cheers.

Cheers!

Good looking scoot! I don't know the zeus so can't comment there... As far as your main jet goes, you *should* be able to change the main jet without messing with the rest of the stack.

It is just the tip….(ahem)…. And it's easy to pull off. Just unscrew the main stack from the carby first. IIRC, Stock main is a 100, so I would order 3 jets. A 106, 104, and a 102.

Start with the 106 and work down until it doesn't feel boggy. Smart money is the 104 will be the winner.

YMMV

Normally UK PX are 96 stock. So Birdsnest advice is sound and hes bang on with calculation of 4+ over stock jet, accept i wouldnt get a 106 it will be way too big. Real Delorto jets are getting pricy now, £6-7 a pop, so you can save a few quid. If you are just doing the pipe, then 4 over standard at 100, if you are going to get the drilled filter then 101/102. I know so many people who run what you have, i have done so myself on my current scoot that was a px125 (now 177) and this jetting is always correct.
As to the zeus, are you sure you really need it? I guess you are doing this to get over the RPM restrictor, but quite frankly you are very unlikely to hit more than 6200 RPM on what you got. I think on the restrictor it starts to plummet way over 6200! Something like 7k. Pop you big jet stack off from under your air filter, get a magnifying glass or use your phone magnifyer and read the number. If it says 96 then do what Birdsnest says, get a 100/102, id be tempted to stay with the 102 for the cold weather and the 100 for the hot. You can get a 101 which is what I ran with the same rig as a compromise balance between seasons. You should really take advantage of the massive 0.5bhp increase with a drilled filter, in which case put in a 102 if you do this. As the px125 is low HP anyway, a 0.5 bhp gain for using a drill is cheap bang for no bucks.

Thanks for correcting me on the PX main size! Should have looked it up before posting.

Yes but you're right , 4 pts over, I do know the jet stack varies outside the uk though .

Well... even if I looked it up I would have gotten it wrong. :-/
Looks like the old (early 80's) P and PX125s were 99/100.

https://scooterhelp.com/scooters/VNX2T.px125e.html

I bet they reduced it due to emissions in later years?

Yep, over here with have all the Euro III, IV, i think we are heading for Euro 6 emissions and safety regs. The PX200 of course was killed off by Euro III, then just the 125 left, leaned up even further, then catalytic converters. At one point they were talking about riders having to have air bag trousers!!! Imagine that on your vespa, a nice jaunt along the seafront in the sun with freaking airbag trousers on. Tightened Euro laws probably the downfall of LML Scooters as ABS dual braking laws came in, etc.

https://www.visordown.com/news/product-news/airbag-motorcycle-trousers-are-now-thing-apparently

*laughs/shakeshead*
"Air bag trousers"

Yes , it's all true. With my cynical head on and likely truth you think that the euro politicians invent a law like this to push through their own interests in manufacturers to make the new requirements and they own shares in them. Can't be true can it, corruption like that ? Ummm I wonder https://www.wantedineurope.com/news/the-european-union-invests-in-airbag-jeans.html

Thanks for the replies much appreciated.