Air Cooled 50cc 103

by Andrew Scouten
Added: • Updated:


UpJet 103! I drove to NYC to pick this bike up, big thanks to Nick UpJet for holding it for me! Since my other 103's are all complex builds, I decided to keep this one simple, Crate motor bottom end, Le Partie CDI, 15 SHA, TSM head, in the pictures it has a Mini Circuit from DOS, and a Teknix cylinder, however I had a cheapo 6 port 50cc Airsal on the shelf, so I swapped to that with a Simonini Circuit I had laying around as well, modified the stock vario, and called it a day. Nothing fancy hear, just your basic 35-40mph Frenchie, reliable, and quick off the line, it will be one of my go to daily's for the 2020 commuting season. UPDATE y'ALLLL This bike was to slow, and at the time I didnt have any air-cooled fast 103's, soooo I tossed a Polini circuit, and a 64cc cast iron Malossi on it! a needed upgrade, now it does 47mph, still using the 15/15 sha, and stays well under 350 degrees (coooool for a 70cc Frenchie!) UPDATE UPDATE: I blew this bike up in Nashville, so it was back to the drawing board, kinda twice. I rebuilt the engine with.....fresh bearings/seals/crank/cases/50cc Airsal/clutchless ER3/Doppler ER86 Pulley (the crap pulley)/Athena reeds/15 SHA, and it was riding again! But I felt it was a little slow for all those clutch parts, then came DOS....These fine people re-popped the 64cc W-port Liquid Cooled Polini, and I couldnt resist it. So I slapped the Polini on, tossed a likely to small (but hey it worked on another lc bike in the past) radiator, plumped it with a overflow bottle and the intentions of relying heavily on my overflow to keep it cool. it started right up, but damn its winter here in Ohio, more tuning and possible pipe changing to come in the Spring. THE SAGA CONTINUES: After some tuning this summer, and some hassling from Jim Henry, I decided this bike needed a few things, first a pump. So I added a regulator/rectifier to convert the ac charge coming off the stator to DC, stepped down to 12v, with a battery (giant cause if your gonna do something, over do it) in line, so basically the stator powers the pump but at idle the battery makes up for the loss of power. Next I switched from a 15 sha to a 19 Polini CP, and finally I ditched that shitty pipe for a Ninja with a broken baffle (hence the heat tape keeping it all together). Oh and a kill switch, since ahhh one time the carb fell off and the air leak about sent me into a wall at 50mph. So Ya this thing is tuned, the pump really helps, the pipe is kinda low, but thats the French life I guess, shockingly it doesn't rub on hard right turns. All in all Im very happy with this bike, go fast, have fun, ride French.






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