Modern Vespa

Hi all
I have a Vmc Super G kit ( bolt on) with a Bgm fast flow carb, fast flow tap, filter heart drilled,and a polini box exhaust on a px125

Jetting is AC160 BE3 MJ 130. idle 160/55

Is there any advantage to removing the air filter but leaving the bellows to frame in place, l.e. more power. ( I'm looking for grunt as the scoot will have a sidecar attached)

Also in theory if I did so would just a bigger main jet be needed or would the whole stack and idle jet need changing.
Appreciate your thoughts Andy

On its own getting rid of the filter will not gain you anything, fitting a bell will and then you have to decide if/where you want a filter.

lot's of discussion on the topic here:
Bell-mouth intake

Thanks for the heads up, will have a read.

I'm all for it. Running without a stock style filter is the next best to a bell mouth. However, if not up jetted enough your G will loose it's Super very quickly.

Assume this is a 20/20 carb as it was a 125. First thing to change is the AC160. Possibly a 140 but if you need to buy one get an AC120. One this is changed the other jets can be tested.

Sorry thought I'd said, carb is a 24 24, thanks for your insight, question?
Are we only taking about top end improvement or does it help across the rev range? And what sort of MJ change would be a good starting point assuming a 140 AC ( no point in keeping the 160 and moving the main jet even higher?)
You'll have to forgive me if the questions are basic, trying to understand what's going on with the jetting , the whys and wherefores

The first step is to set the main jet to the AC. Use the biggest main jet you have, even if it's 150. Run it as it will be, bellows on , box top on, no filter. At all times the same way. Each of these affect jetting.

What should happen. When fully hot, wide open throttle (WOT) in 2nd gear should splutter so much it won't rev out and feel so bad you can't ride it anywhere. Once at this stage, main jet can be reduced one at a time, until it nearly revs out. This jet number will dictate what to do next. Ignore any issues that occur when not wide open.
Might be snowing Tues, so tomorrow or the weekend.

Thanks Jack, will give it a go and see what happens, thank you and I'll let you know how it goes/ pester you for more info

Just read your topic and found it fascinating( and hats of to you young man for your ingenuity)
Did you ever manage to quantify the improvement the bell mouth gave you on the 24/24 and where in the rev range it happened?