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 17.5mm or 19mm for Buggeye sport cylinder 
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Joined: Sat Aug 05, 2017 8:39 am
Posts: 36
Location: Arroyo Grande, CA
scooters and mods: 2005 Zuma, Athena alu. Sport 70cc, Giannelli Reverse pipe, NCY variator and clutch, UNI flat filter in 125cc airbox,
Post 17.5mm or 19mm for Buggeye sport cylinder
Forgive me for asking this as I'm sure it's been answered/explained somewhere on here but I just cannot seem to find the info by searching.

I am finally completely fed up with the stock carb and want to upgrade to either a 17.5mm or 19mm Delorto for my Athena 70cc sport (10mm) (aluminum) cylinder. What are the pro's and cons of both? I definitely want to keep my stock airbox but will I need to upgrade my intake and reeds/cage? Since I'm already running an aluminum sport cyl. and Gianelli reverse (high RPM pipe) would it be bad to try and tone it down (still running 10mm crank bearing) with a smaller carb like the 17.5 or would it be best suited to run the 19mm as to match the intent of the sport cyl. and pipe?

2005 Zuma 50, Athena Race BBK, Giannelli Reverse exhaust, NYC Transmission kit, Dual Headlight LED's, 125cc airbox & filter, carbon reeds in stock block, vented CVT cover, moto style kickstand, moto number plate stickers (+1/2HP)LOL,

Sat May 25, 2019 6:15 am
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Joined: Fri Aug 31, 2018 5:18 pm
Posts: 623
Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: 17.5mm or 19mm for Buggeye sport cylinder
Code good to see you back
here is a reference with dynos ... comparison

I am looking at a new carb it is on my christmas list so I am early in figuring this out .
I have a graph saved somewhere from a different scooter shop that 17.5 works for up to mid race cylinder and pipes after that a 19mm starts to work better .

A 19mm works for sports 70 up to race .

So for me I will take the one I get a better deal on because I will stay at a sport build .

This thread seems to lean toward the 17.5 or imply it also is good enough


2004 Vinos Derestricted exhaust and variator stock carb with mikuni 70 main jet needle down 1 clip 40 mph
Athena Sport BBK waiting to go on

2004 Vino Malossi sport 70cc Malossi Wild Lion pipe malossi multivar 6.5 sliders green polini clutch springs stock carb 75 mikuni main one clip rich 47.5 mph Michelin S1 90/90/10 rear tire Michelin S1 3" x 10 up front

2004 Zuma Malossi sport 70 cc Technigas next r 2008 zuma torque driver polini high speed variator 5.5 grams sliders malossi delta clutch yellow contra yellow clutch springs Stock Carb 84 main jet 46 pilot jet needle 1 clip rich stock athena 14/42 gears 11 to 1 final ratio 56 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich (sold)

Sat May 25, 2019 7:04 am
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Joined: Wed Mar 16, 2011 9:25 pm
Posts: 742
Post Re: 17.5mm or 19mm for Buggeye sport cylinder
Based on the reports I've always heard in the past, a 19 mm may be a bit wasted. It's not bad, it's just not necessary. Main con weighing against a 19 mm is that many people report that they end up being difficult to get into tune. As for trying to "tone it down" I'm not entirely sure what you're implying. If you're thinking about rpms, then the carb won't have any bearing on that.

Stock '05 Zuma - in the wild somewhere.
2015 Zuma - Stock. For now.

Sat Jun 08, 2019 3:17 pm
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