Vespa Grande: dellorto 13/13 jetting & air fil

You guys convinced me,...I just bought the dellorto 13/13 for my Grande. I don't want to buy 15 jets though, can you guys give me a rough idea of what jet sizes I should pick up to start? I wiki'ed it, and I couldn't find anything that specific.

My Grande is completely stock, with the exception of a Malossi Multivar Variator (currently 4.6g weights) and a tecno circuit pipe. So what range of jets sizes should I start with,.......and what jet size would you guys suggest I install first and work from?

Also, I am going to buy a performance air filter, as suggested. I was going to buy the Malossi from Zippy,.....or is there an air filter that's better than the Malossi for Vespa Grandes? The only ones I could even find were the Malossi and a generic one from treatshq.

Thanks again, everyone. I can't tell you how much I appreciate all the help from everyone. You guys are awesome for taking your personal time to help a dumbass novice like me.

Re: Vespa Grande: dellorto 13/13 jetting & air

This is a good place to start:

"Moped Tuning Sheet":

You can see there what other people have done. It looks like mid 60s would be a good place to start.

Re: Vespa Grande: dellorto 13/13 jetting & air

the tuning spreadsheet is very helpful. From the looks of it a 64 jet looks popular with a your setup. remember you have to take in to account altitude and temperature of your location. oh and for air filters those are your two options I couldn't tell you which one flows more but I have the generic one and I can't imagine the Malossi one flows more cause the one from treats has very corse open cell meshy foam. but more isn't always better.

Re: Vespa Grande: dellorto 13/13 jetting & air

Thanks for those that spreadsheet guys,.....that was a big help.

Paul, you said to account for temperature and altitude. I am in Hollywood - warm and dry. I'm 12 miles from the ocean, so I would guess that I am close to sea level. How exactly do I determine what effects that will have on my jetting? My guess is hotter weather would make you run richer, because everything is expanding? But I have no clue, that's just a dumbass guess. When you get time, I would love if you could explain it to me. I have wiki'ed a ton of carb info - but I didn't recall seeing anything about altitude and temperature effect.

Thanks again.

Re: Vespa Grande: dellorto 13/13 jetting & air

it pretty much has to do with the density of air and amount of water molecules in it.

if the air is thin (high altitude) and/or the there is a lot of humidity (more % water in the air) you need a smaller jet (which controls the fuel flow) to keep the proportion of gas/oil to air. in denser air with less humidity, there is more % oxygen so you can use a larger jet (more gas) to keep the fuel/air mixture balanced for the ignition (explosion in front of the piston).

Re: Vespa Grande: dellorto 13/13 jetting & air

Excellent breakdown.

So if most people are running 64 jets (which seems to be the case),...I'll probably end up around a 66 jet in dry, low altitude So Cal.

Re: Vespa Grande: dellorto 13/13 jetting & air

yeah, 64 or 66 might be good starts. many folks get the jetting right by looking at the spark plug (plug chop) after riding hard for a mile or so. grey/white too lean, mucky black too rich. i usually use the biggest jet until the engine 4-strokes (gets bogged down, goes faster if i let off the throttle) and use the next smallest jet size. maybe two sizes smaller. hope this helps

Re: Vespa Grande: dellorto 13/13 jetting & air

you got it. but the 64 might be better for you because it is warm in LA and warm is less dense than cold, thus less oxygen. I like to jet my bike so that it runs a little better on a cold night so that I don't end up lean when I'm out blasting with my friends on said night. As said above the plug is your best indicator as to whats going on in the combustion chamber. You want the porcelain insulator to be the color of coffee with cream. not light tan and not dark brown.

Re: Vespa Grande: dellorto 13/13 jetting & air

Jetting is not so sensitive that one size bigger or smaller will make or break it. So I'd say get like 62, 64, 66 comes in the carb, a 68 and a 70. You could really even skip every two if you want.

Re: Vespa Grande: dellorto 13/13 jetting & air

im running a 70 jet in my 13.13 carb on a 65cc kit.

I feel like its a little strange though, i may have a small air leak

im ripping though. so who knows.

Re: Vespa Grande: dellorto 13/13 jetting & air

that does sound a bit big. I would check for a leak.

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