Converting from stock Gurtner AR carburetor to a Dellorto SHA carburetor
The Gurtner carburetor is an oft-malgned piece of equipment that can function well and supply adequate performance for the motobecane user. It has the additional benefit of being design to work with the supplementary systems on a Motobecane, and so installation and maintenance is fairly easy. That being said, Gurtner AR's can be difficult to clean after being ravaged by time and the elements. NOS replacements can be difficult to find and pricey, so a number of riders over the years have looked to replacing the carb with a readily available and adaptable Dellorto SHA style carburetor. There is the additional benefit of swapping out a small, restrictive carburetor for a larger, 12mm(Dellorto SHA 14/12) or 15mm (Dellorto SHA 15\15) body.
- Use the bendy 14mm intake, available from Handy Bikes or 30MPH parts engines.
- Use the click choke model SHA carb body.
- Cut your throttle slide so you can pull the cable enough to open the carb all the way and let it close enough to idle.
- Use a #57 jet.
- Tilting the carb clockwise when looking at it from the moped’s starboard side will help.
- Some say using the Gurtner cable guides will help.
- If you have a variator I recommend removing 1 or two ball weights in order to utilise the newfound engine speed capacity. See guide on Motobecane Variator Repair and Tuning.