Aprilia SR50 MotoIQ.com Project bike

Project Aprilia SR50: 100 mpg Madness Part 1, Basic Bolt on Stuff

By Mike Kojima

A few years back, if you rode a scooter, most people would immediately write you off as a dork or some sort of lame PeeWee Herman sort of deviant. With rising gas prices, scooters have started to become an interesting alternative to cars, especially in urban areas as they are small, easy to park and their automatic transmissions deal with traffic and other urban hassles with greater ease than a motorcycle's manual transmission. They are also amazingly cheap to insure. With practical necessity, scooters are becoming more accepted and are quickly becoming fashionable transportation among urban hipsters with a culture all their own.

Read Part 2 here!

pee wee herman  you are a giant dork

Perhaps you have seen the MotoIQ approach to scooter culture if you have been reading our exceedingly popular Project Ruckus series. We took a pedestrian 50cc Honda Scooter and turned it into an urban assault vehicle capable of taking on the toughest urban commuter traffic. In other parts of the world Scooter Tuning is a huge market, perhaps bigger than the car tuning market in this country. At MotoIQ, we want to bring you some of this continental culture to show that you can tread lightly but still have fun. Modding a scooter is cheap compared to a car and having economical back up transportation means that you can take more time to build your car correctly or park it for awhile if it is costing you too much to run instead of having to sell it.

Our new two wheel project is a very unique machine; it is an Aprilia SR50, perhaps the most advanced scooter on the market. It uses a hi tech, Orbital engine which combines the compactness and power density of a two stroke engine with the fuel economy and low emissions of a tiny four stroke. The Aprilia engine uses licensed Orbital technology which is basically An ECU controlled, directly injected, stratified charge two stroke. Two strokes by nature produce pretty low NOX emissions due to their low operating cylinder pressures but are terrible for hydrocarbons as they tend to blow raw fuel out the exhaust port on overlap.

Aprilia orbital engine

On the Aprilia’s Orbital engine, an electronic fuel injector puts the fuel directly into the combustion chamber after the exhaust port is closed, eliminating hydrocarbons blown out the exhaust port. The fuel is atomized by a burst of electronically metered high pressure air from a crank driven air pump. The burst of air and fuel is disbursed to a rich zone located around the spark plug. This rich area is easily ignited and helps support combustion in the leaner remainder of the cylinder. With this lean-burn system the Aprilia engine can run at air/fuel ratios as lean as 25:1 and can safely run as lean as 16:1 even at wide open throttle.  Unlike other two strokes the fuel is completely kept out of the crankcase so the amount being metered into the engine is precisely controlled with no uncontrolled fuel wetted areas. This greatly helps emissions and fuel economy compared to conventional two strokes.

Aprilia Orbital direct injection system

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Monday, November 30, 2009 7:02 AM
I want you to do a mod of the Sach's Madass scooter and then the SYM Symba!

(Honda Cub distant relations)

Monday, November 30, 2009 2:27 PM
Mike, you should have picked up a Yamaha Aerox:
Or perhaps a Italjet Dragster:
Mike Kojima
Mike Kojimalink
Monday, November 30, 2009 4:15 PM
I want an Aerox bad, they have killer parts for it but they don't sell it here in the USA! You can build them with 26+ hp with just off the shelf parts!
Friday, December 04, 2009 1:28 PM
I know because I owned few of them !
Everything Polini. Bumped up the Compression to 14.1:1 displacement to 90cc. Got a bigger radiator. Dell'Orto carburator 24 mill. When I was done tuning the carb with the right jet I was pulling away (in acceleration) from regular 125cc Cagiva Mito (2 strokes)...good times.
Unfortunately my scooter was so fast it caught too much attention and it got stolen (at one point it reached about 75 mph)....a full tank of gas lasted about 2 days....haha.
Mike Kojima
Mike Kojimalink
Friday, December 04, 2009 6:55 PM
Where did you live? I would have put a 28mm on it.
Wednesday, December 09, 2009 9:46 PM
I spend my childhood in Switzerland til 13, then moved to Japan til 18, and now here in the US.
Another popular moped to modify was the Piaggio Si and Ciao, also 50cc air cooled. Polini made everything for it.....lots of good times....hehe
Thursday, December 24, 2009 9:53 AM
Hey Y'all - Can anybody tell me what kind of front rotor is on this SR50 - I'm lovin it and want to find one - also, any like recommendations for the rear as well -

Many thanks for any help ...
Mike Kojima
Mike Kojimalink
Monday, December 28, 2009 4:46 PM
The front is a stage 6 the rear a Galfer.
cameron campbell
cameron campbelllink
Monday, December 26, 2011 2:06 PM
i just found this and i thought this was great. i have been driving peds for about 4 years. i just got an sr50 and the project yall did is extreamly helpfull
Saturday, June 23, 2012 5:27 PM
I was just wondering where exactly you guys bought the European side cover for the transmission. I need one of those. My next question is do the European SR50's use a different airbox that is slimmer? Im just wondering if it will look strange with the big plastic airbox and a polished cover. I would use an open filter like you guys did but I ride in all weather conditions.
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