Modern Vespa

Morning and Random question.

Does anyone know the difference/ why jetting May be different S1 and S2 gs?

I pulled a carb to bits and rebuilt and was surprised it had a 115 main. Seemed large. Scooterhelp verified this was right for a S2. I wondered if anyone knew why the jump from 108 for S1? Is this possibly a typo on Scooterhelp? Did match my carb though…

Reason is most likely will ride with a sip (conversion stub) and gotta start with some upjets and wondered where to begin!

Thanks heaps.

According the information I found in some workshop manuals there was some kind of "recall" on the GS160.
This page is not available in all workshop manuals available in the web.
I use the 115 with the BE3 in combination with the Sito exhaust without any problems (sea level).

Translated:

To avoid on the Vespa G.S. mod. VSB1 that the carburation is rich, that the consumption is not regular and that there is little power, in addition to carrying out the maintenance operations indicated in the tab from p. 11, make sure that the air intake opening located under the seat is not partial or obstructed.

To eliminate the inconvenience, if necessary, make the following modifications to Vespas G.S. up to VSB 1 T-0029901.
1) Replace the pre-existing purifier groups - air filter, bellows, joint between link elbow and frame with the corresponding new ones indicated in the update to the PR catalog (purifier with filtering group on top; bellows shortened; larger joint thickness).
2) Apply the tube designed to discharge the waste mixture to the outside of the purifier box.
3) Replace the gicleur of! max of 108/100 with the gicleur of 115/100 ; the pre-existing emulsifier, marked E1, with the new marking BE3 or BE2.
4) Replace (only in vehicles prior to VSB 1 T. 0025248) the pre-existing gas valve with the new valve indicated in the catalog update, with a radiated central cavity and a square shape.

Quite large difference between the early pepper can and the later flat filter in a box.

^^

Thanks, yeah. Thats sort of what I was thinking.

Although its kind of just a visual thing? Air going into a carb?

And Pilif, hard to read with translate, but seems there may have been some sort of recall on the 108s.

Im going to take 115 as a starter!

This is all very interesting to me. I have run a 108 in my GS160 Mark II since I owned it and I've never really felt that it has run smoothly. After completing my SS180, I have really noticed how much smoother it runs than the GS. The SS has a 115.

The GS seems to have the symptoms that Pilaf is describing. After reading this, I'm going to change out the 108 on the GS to a 115 and see what happens.

May help i reckon.

Just as an extra, the whole stack seems different, which also corresponds with Pilafs notes. I didn't look at the whole thing, but will check now.

Flick between S1 and S2 to see.

https://www.scooterhelp.com/scooters/VSB2.GS160.html

All this time using the wrong main jet.

Just checked, and my whole set up same as S2 version listed by scooterhelp. BE3 etc.

Could be worse. May be like discovering a favourite if it runs better.

The ss may still trump it though! I think they went to 180 for a reason…

I think the SS trumps the GS in a couple ways. The engine is smoother running, a bit higher top speed, and more comfortable sitting in its frame geometry. Having said that, I still love my GS.

Good lord. I just changed it to a 115 and it runs purrrfectly now. It has smooth, powerful acceleration unlike before.

It's never too late to get things right, but that's a tough one to take. All these years (about 10) running sub-par on the "correct" 108 jet, informed of recall and now perfect on the 115.

Thank you to everyone here, especially Pilaf. I'm stoked!

nomadinsiam Glad the problem is solved after all these years. I've solved the "115 jet issue" after removing the points ignition and installing a Vespatronic. Couldn't get it right after installing and finetuning the sparkgap and timing. Then I went back into the "old" books and found this jet information. Suddenly all my issues were gone and I expected a more black and rich sparkplug but is was the same coffee color as before.
At the wintertime maintenance I found out that the on the piston and between the rings there was a lot more coal deposit. I adjusted the timing of the Vespatronic back to the factory default (26 degrees at 2000rpm) instead of the advised 23 degrees by Vespatronic. I also increased the sparkgap to 0,7mm instead of 0,5mm since the spark given by the Vespatronic CDI is more powerful than the old 6v ignition coil. It is running a bit hotter (but well within limits) than before, but most important a lot cleaner.

I plan on keeping it 6 volt points, but thanks for the information.