Vespa Tuning/Gearing Q's

Hey guys, I've been tuning my Ciao for a little bit now trying to get it dialed in and it's getting pretty close and running really well! However, I'm having an issue getting it to go faster than about 32mph on the flats. Here's the setup:

-DR43 lightly case matched, Malossi head w/gasket, ported 13mm intake, opened contact patch (not too big), Mazzu anticipato crank, Gianelli Fire.

-13:13 SHA, 70 or 72 jet (can't remember exactly which atm)

-Points set at .016

-Polini Variator, 6g weights

-Malossi belt

-Stock Euro clutch with Malossi black springs (2000rpm clutch engagement), aftermarket steel bellhousing

-12.5 : 1 gears in the transmission on Si cross mags

The engine runs good with a steady idle, has good pull throughout the powerband, gets up to speed quickly and can pull pretty decent hills at ok speeds. I feel the variator is tuned pretty spot on as the pipe comes on and pulls right in the beginning of variation and pulls it to full variation plus a few more rpm after that. After that though it's like it hits a wall even though the engine is pretty up there in RPM's. I've messed with the jetting and different weights up and down the range with little difference in top speed (unless of course I tune it too far out in which top speed suffers).

I'm wondering if maybe the transmission gears are the limiting factor here? Or maybe the pipe just can't hang? What are other people with a DR and variators + super low gears pulling for top speed? I've searched the forums and have found other people experiencing the same issues but never a resolution, I really wonder what's causing the issue.

Any Vespa gurus have some sage advice? (edited)

Re: Vespa Tuning/Gearing Q's

What contra spring are you using? Are you running 90mm clutch cheeks or 100mm clutch cheeks? Have you used a marker on the variator cheeks to ensure you are getting full variation? My grande has a similar setup and it tops out at 43mph on 12.25:1 gearing.

Re: Vespa Tuning/Gearing Q's

Stock contra spring, 100mm pulleys on a Euro clutch. I haven't marked the variator cheeks but I can see it variating as far as it will go, if I set it up with much heavier weights it'll start to variate right as the clutches grab and won't let it pull high RPM. Right now it's variating through and still pulling a little more RPM after that.

Re: Vespa Tuning/Gearing Q's

I had issues with my euro clutch not allowing the belt to variate all the way. Here’s a thread I made about it.

https://www.mopedarmy.com/forums/read.php?7,4105776

What I would do is pull the clutch apart and reassemble without the contra spring and pull the belt by hand between the cheeks to see how far down it will go.

Re: Vespa Tuning/Gearing Q's

something holding you back from getting to low 40's, don't think its the gearing,

Re: Vespa Tuning/Gearing Q's

I double checked the rear clutch, it doesn't look like the clutch shoes or anything else is coming in contact with the pulley. I marked the variator and the belt only rides 3/4 of the way up but when I take the belt off and close the variator I can see that where the belt is riding at top RPM is where the variator cheeks are completely closed.

I was just riding it around to see how the variator/clutches looked at certain RPMs and the rear variator somehow got stuck into the "open" position and I'm unable to close it, don't know how that could happen considering the contra is pushing on that inner cheek. I guess I'll pull the clutch, swap out contras and make sure everything is opening as far as it should but everything looked like it was moving how it was supposed to before the clutch just did this bs. These things are more of a headache than French bikes

Re: Vespa Tuning/Gearing Q's

Jeremy Edwards /

I have a ciao with polini 63 kit including head, proma circuit exhaust, modified casings and crank, malossi variator and belt, 13 carb and I find that I can't go above a 60 jet in the carb, mine runs best with a 58 and I can get 38-40mph but it is screaming at that and you certainly couldn't hold it at those speeds for long without doing damage but I do find it's got good acceleration and plenty of power for hills and will cruise fairly comfortably at 33 though, I actually expected an easy 45 with that set up but there is no way it would ever get to that with standard gearing. I think a 70+ jet is huge for that set up and think you could possibly have an air leak somewhere, as I said mine runs best on a 58 with a 70+ it wouldn't even idle without having the screw nearly all the way in, the instructions for my kit states that it works best with jets between 52 and 56 and I find that a 58 just gives it a little more power without sacrificing top speed which to me that indicates my engine is working as it should and the fact you are on such a big jet further confirms to me you have a leak somewhere, most likely at the base of the barrel but other possible areas to check are the joint in the engine casings and the oil seal behind the points, I also had the same issue with the variator only going 3/4 of the way and I modified it so it now runs to the top but in all honesty I didn't think it made a noticable difference so I wouldn't blame that for now. I will be interested to know if you have managed to get any further forward with yours?

Re: Vespa Tuning/Gearing Q's

yes to the air leak at the base gasket, on one of the transfer edges it thin like 1mm, you can find it by spraying carb cleaner on it and it'll die.

I cleaned and added a chunk of jb weld to seal.

Re: Vespa Tuning/Gearing Q's

Have you tried lighter than 6g? You may still be over variating not letting it rev out

Re: Vespa Tuning/Gearing Q's

I would check that nothing is binding too, sometimes the front vari can rub the frame, gearbox tight, old gear oil, brakes. I dunno, that setup should be jamming.

Re: Vespa Tuning/Gearing Q's

Jeremy Edwards /

Yes I had to do the same on engine casings, as the area for gasket was so thin it would prob never have sealed. I think the over variation is possible too if still running the standard rear spring, I know with the malossi variator I got a yellow spring which is a fair bit stiffer than standard one and it came with 6g weights for that, although I do feel they were just slightly light prob 6.5g would be better

Re: Vespa Tuning/Gearing Q's

Dirty30 Dillon /

If you didn't use a decent fiber gasket for the base, there's a high likelihood you have a leak. Also, despite the indexing collar (which often gets lost on rebuild) the vespa cases can end up very slightly twisted, leaving high spot-voids at the 12/6 position. When you rebuild it's always a good idea to check that the base surface is as close to perfect at the seams, before you install your engine peripherals. It's easily adjusted by loosening the case bolts and some taps with a rubber mallet.

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