100 MPG Madness: Project Aprilia RS50

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After stripping our bike down, we found that the aluminum frame was in good condition with a clean up.  Most of our bolts were finished in yellow chromate so after a soak in some penetrating oil to dissolve the white corrosion, they looked new.  We sent the wheels off to Embee Performance to be powdercoated and ordered a new set of plastics from AF1.

100 MPG Madness: Project Aprilia RS50
Malossi has this 21mm Dell’Orto carburetor which is much bigger than stock and has all of the fittings so it bolts straight into the RS50 keeping all of the stock stuff in place.

We then disassembled our engine.  To gain more power we got a Malossi 80cc kit from an overseas mail order house.  We shipped the cylinder to AF1 who gave the ports a light clean up.  We did not want to do extensive porting as we did not want to make the powerband too high or narrow.  We then WPC treated the cylinder, piston, rings and wrist pin. (read about the magic of WPC Treatment here!) AF1 supplied a Doppler full circle HD crank.  The crank takes up dead cranckcase volume which helps high RPM breathing on a two stroke and is much stronger, allowing the engine to rev beyond 12,000 rpm safely.

100 MPG Madness: Project Aprilia RS50
The Malossi carb totally dwarfs the stocker on the right, it has to be 3x bigger!  The stock carb has water heating, probably for smog reasons.  We had to bypass the water lines as the Malossi part has no provisions for water heating.

The transmission is a weak point on built AM6 engines so we cryo treated all of the gears and shafts then subjected them to a severe shotpeening with hardened shot.  Next we WPC treated the gears. This treatment should help the tranny hold up to our expected power increases. The clutch can’t handle much more power than stock so we replaced the stock clutch with a heavy duty Barnett clutch and clutch springs.

100 MPG Madness: Project Aprilia RS50
Here is the carb in place, it is compatible with the stock intake manifold, throttle linkage, oil injection and airbox.

 

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