Liquid Cooled Head 70cc Peugeot 103

by Andrew Scouten
Added: • Updated:


I was torn on this build, at first I wanted to keep it stock(ish) ported the stock 2-transfer cylinder, added some Tomos Airsal reeds, a small Circuit from DOS, and a 15 Sha, upon jetting I realized the seals, well blown out isn't the right word, I needed a 90 jet to get my temps under 400, just weren't there? So I decided if Im gonna rebuild the motor, I might as well make some upgrades, and I hadn't really built a 70cc 103 before so I said why not? I reused the stock cases, cut a third transfer, new bearings and seals, Doppler crank, I decided on the small port 70cc Airsal, the transfers lined right up and off I went, for the first set up I used a 46mm dcomp-less head, it ran well but as all French bikes do, it had heating issues, so I started looking for an LC head, I was going to use one of the MlM Hobbit 46mm heads but they are a bit pricey, considering Id be taking a dremel to them anyhow....150ish $...Now here's the deal 103 stud spacing is 70mm, hobbits are 67.5mm, so I found a guy who made a 47mm LC hobbit head, he was running m7 studs, so that meant he was at about 68.5mm, I took a 9mm drill bit and opened them up, now they were 69.5mm (NICE) and close enough. Boom head on, thermosyphon to the rescue again, temps well under 300 degrees. I modded up the stock vario in the traditional fashion, and boom we have a little ripper UPDATE I moved the radiator, and added a Polini engine spring, fuck me this thing will rip your dick off, viva la France! UPDATE UPDATE: I removed the LC head in an effort to simplify this bike, replaced it with a Treats Modified Derbi head, also while I loved that simple Polini Utah pipe, it snapped like 3 times, so I replaced it wit this mystery pipe I had on my shelf. Still does 50, still lots of fun!


1978 Peugeot 103SP




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