Modern Vespa

I finally got my v90 buttoned back up and took it on a ride around the neighborhood. First time its been on the road in three years I think. Gotta tune the sucker now.

'70s v90 engine, stock crank and gears
Malossi 135 topend, didn't do any case matching or such.
This Simonini pipe, https://www.vespatime.it/default.asp?cmd=getProd&cmdID=3089
Indian ebay electronic ignition
Stock 19.19 SHB carb

Its super rich right now. I wanna say I stuck a 100 jet in there when I was putting things together. I've gotten used to tuning mopeds and modern 50cc scoots, they tend to like big carbs and lots of fuel. Any suggestions on what a good starting point on jetting would be?

Is that enough carb for this kit?

I never did any research before buying the Simonini pipe, I just bought it on a whim.

I would hazard a guess that if you are on 19mm carb, your jetting is too high, this would likely run as is, more like an ET3/ETS performance if it were me id start with a 90 main and work down from there. The ETS 125 haf a 20mm carb and standard jetting is 76 main. I think the ET3 with 19mm carb is around same area. So from 90 going down i think you are in the right area. Buy a jet kit, cheapest way of doing, right royal pain in the ass taking tank and carb out each time to change jet. Im assuming your malossi kit is an early one? I seem to remember most folks recommending a 20-24mm carb for the early malossi?? However, if youre on standard 90 gearing, I dont think you are gonna get the full top end potential with standard 90 gearing; 19mm might do for nipping about on around town until you change your gearing that is best suited to the kit. You need a small frame guru to pop by here to help.

Yeah, I got jets for days at least. I just started big because that what my 50cc t-n-g brain said.
I'm not sure if this is considered the "old" or "new" 135 kit. It's this one…
https://www.scooterwest.com/malossi-135cc-cylinder-kit-w-head-for-vespa-small-frame-m315260.html

The carb had a 74 in it and I just felt that would be seize city. Running a 19mm carb with a 90 or smaller jet on a 135 engine is hard for me to get my head around. Last engine I took the time to really tune to the gills was a 70cc topend that wasn't happy until it got a 21mm phbg and was jetted around 110. Kind of fun having a 70 mph "49cc" bike. I know that's much higher rpms and massive transfers compared to my v90 though.
If after some dialing in it really doesn't like the 19.19 I do have some bigger carbs I can try on there, I'd just have to figure out mounting.
I'm on a hard moratorium on spending money, so gotta stick with what I have in the shed already, I'd really like to get the reed kit that goes with this topend.

Oh yeah, and I'm not really chasing more top end than I was getting before. The bike would previously (100 cylinder, Polk I pipe) top out just above 50mph and that felt sketchy to me. I just like the idea of getting to 50 faster than everyone else.

If I just wanna harass the GY6 guys I have a mildly tuned Stella, if I actually need to go fast I have a 96ci Dyna.

My old Polini 135, 19/19 stock carb with Malossi exhaust (not as performance as yours) ran an 80 jet. A few points richer than stock. That was with a 4 speed gearbox! The 3 speed gearing/load on yours might cause some jetting headaches FYI.

Try an 85 and see if that feels better than the 90. Start rich and work your way down, seeing what gives you full rpm under load.

The good thing about the m6 jets you can now get them in one point steps to get them fairly bang on. When I say bang on, dependent on climate and season as my scoots lean out in winter. My pk75 with 20mm shbl carb and bgm pro box pipe reaches just over 50mph with no kitting. That runs a 78 main jet. I think malossi are now selling the mk3 kit , I don't know the differences from early type to newer, probably metal used,amout of ports and induction ; dual inductions, reeds etc .

That simonini pipe looks real nice. Says you need to jet up 5 pts just for that pipe alone. Bet it sounds like a dirt bike. Can you YouTube it all once you're done as would love to see and hear it. I had a a 1976 v90 years back and top speed was 42mph, still loved it despite its limits.

Getting it dialed in. Still tops out right around 50 which is what I expected. Big difference is I can pretty much stay in 2nd while in traffic and not have to keep shifting up and down to keep up.

if you've still got the V90 primary, with a 3spd and that carb you're not going to see much more than 50. dialing it in will make it smoother and better running though.

that kit likes a 24/25 and with that pipe it would be really smooth. keeping the V90 primary and a 4spd you'd be in power wheelie territory for 2nd gear and you'd have legs in 3rd.

I'm not that interested in splitting the cases right now. I have another smallie engine that the plan is to do a long term build with all the fun parts.

I do have a 21mm PHBG I figured I'd try on there at some point.

Clutch seems to have decided to start slipping too, so I can't enjoy the improved launch to its fullest.

Sorry to interject in this thread.. Just curious if swapping 3 spd to 4 spd small frame needs a change to the shifter arm on the engine, or if it's just the full gearbox/axle switch itself and nothing else needed?

Just this?
https://www.sip-scootershop.com/en/product/gearbox-kit-58-54-50-46-teeth-4-gear-pk_134907J0

Good info from this thread about how critical the extra gearing is for upgraded kits on the v90. I never would have guessed keeping the 3 speed would restrict his performance that much! Not sure what the stock v90 top speed is, but assuming it's close to v100.. I barely break 40-45mph so throwing a kit on it alone would really be an incomplete upgrade only providing about 5-10mph increase top speed, with money invested in the upgrade left locked up in the missing fourth gear. It's almost like you gotta spend double to make the kit worth it.

nope, arm stays the same. if you've got it apart, knock some new o-rings in there and if it's high mileage check the bronze bush and blocks on the stirrups. other than that it just all knocks together.

it's a slippery slope tuning wise. snapping a kit on with a stock carb and 3spd with a banana will make a difference, but you have a massive 2~3 gap and the kit loses all those RPM where it likes to huff. it'll do 50ish, but takes a hot minute to get there and you have nothing else left once there. adding a decent pipe to that set up doesn't yield much in results, because you're still operating with the stock carb.

ideally, an upgraded carb and exhaust with the right gears is what you want to shoot for when throwing on a kit. a DR with a stock 19 and a noisemaker with a 4spd will do 55 all day. with a bigger carb and better pipe, you'd probably see an 8~10mph increase.

I'm not saying you have to go hog wild, but you can build something decent without reeds, a 30 carb and some gnarly pipe.

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Many moons ago in 1983 I had a v100 and a v90 at the same time. Bought the v90 cheap to sell on. The v90 wouldn't go more than 42mph , the v100 with a fresco (the only tuning pipe we could get at that time) would go Off the 50 mph clock all day long. The 90 was a slouch , the v100 would burn off derestricted gilera 50 motorcycles and Yamaha fs1es and we're rapid.

Probably not as fast with 220 lbs on it!

That 2-3 shift is still a bear but at least with the 135 kit it doesn't completely fall on its face if I'm not totally revved out in 2nd.

I'm not 100% sure I need a fresh clutch now, it may have just dried out from sitting so long it was unhappy. Or I'm just getting used to the slip and adjusting my throttle/shift habits? I've spent enough time on tuned single speed mopeds that my brain feels a clutch should slip some off the line, lol.

I'm about 250. I was getting just over 50 out of my v90 with a 100 jug, Polini pipe, SHB 16 carb.