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When letting out the clutch, I have to get the revs pretty damn high, and feather the clutch to get going. This has led to inadvertent burnouts on slight hills when trying to not roll backwards, or just stalling out, and having to roll backwards out of traffic.

After cleaning up the carb, I picked up the stock jet stack listed here: [/url]https://scooterlounge.com/vespa/reference-library/vespa-stock-jetting-reference-guide.shtml[url]

Everything after 1/3 throttle feels pretty good. But the take off is god awful.

This diagram [/url]https://modernvespa.com/forum/wiki-guide-si-jetting-chart-how-to-tune-an-si-carb[/url] makes me think it's the AC/idle jet/mixture screw, but im not sure which one to immediately go after.

Any ideas?
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Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
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Location: The state of insanity, SoCal
 
Sergeant at Arms
@greasy125 avatar
Weird 80's Vespas & Cool Vintage Lambrettas
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Location: The state of insanity, SoCal
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Guide: SI Jetting Chart + How to Tune an SI Carb

read up on that, bunches of info and pointers.

but cover the obvious first. look for airleaks at the carb base or carb box due to something being loose.

having to rev out to get moving could also be a clutch issue. have you had that open for inspection yet?
⚠️ Last edited by greasy125 on UTC; edited 1 time
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Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Location: London UK
 
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Location: London UK
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Did you replace the pilot jet? And same issue before and after?

Post some sound recording and we'll be able to hear what's going on.
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So the previous owner had a 94 main, E3 atomizer, and 140ac . After things started running wonky, I swapped for a 100main, BE3, 160ac, since thats supposedly the stock configuration, but didnt really help.

This morning, i put in the 100main,E3, and 140ac. Seems to be running much better. It doesnt fall on its face when i crack the throttle to take off.

Im not hip to all the SI voodoo. Does this combo make sense?
⚠️ Last edited by coastalviews on UTC; edited 2 times
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greasy125 wrote:
Guide: SI Jetting Chart + How to Tune an SI Carb

read up on that, bunches of info and pointers.

but cover the obvious first. look for airleaks at the carb base or carb box due to something being loose.

having to rev out to get moving could also be a clutch issue. have you had that open for inspection yet?
I havent opened it yet. When I got this thing, there was a little over 1k miles on the odometer. It looked like someone dumped it a few times while learning to ride, and then eventually gave up. When I went to replace the brake shoes, cables, etc, it all looked brand new.
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