Velosolex/Solex General Information
Spark Plug -
all models (except Tenor / 8000) -
Champion L86 / L86C
Bosch W7AC , W8AC
NGK B6HS , B5HS
AC 44L, 44F
Marchal CR 36, V 36
Denso W16FS, W16FS-U
Spark Plug gap: 0.5 mm
Fuel Mixture -
Always mix your fuel in a clean, separate container.
Never add oil directly to the Solex fuel tank.
Avoid fuels that contain ethanol.
Ethanol is damaging to 2-stroke engines in general, and is especially damaging to the rubber and plastic pieces of the Solex fuel system. It will swell the fuel tank cap, distort the fuel tank causing the halves to separate, distort the fuel pump seating piece and fuel filters, and wrinkle the fuel pump membrane.
~ Models 45 cc, 330, 660, 1010, 1400, 1700, 2200 V1 -
3% , 33:1
4 ounces of oil mixed with one gallon of ethanol-free gasoline
~Models 2200 V2, S 3300, S 3800, 4600, 5000, Micron -
3 ounces of oil mixed with one gallon of ethanol-free gasoline
Use semi-synthetic / synthetic blend 2-cycle oil.
Do not use full synthetic oil.
Full synthetic oil is designed for high RPM engines with tight clearances. On a sloppy, low RPM engine like a Solex, it will leave a film on the piston and cylinder that will lead to over-heating.
Velosolex Solex websites:
Solex 3800 USA : https://solex3800usa.over-blog.com 
Velosolex 4600 : https://velosolex4600.over-blog.com 
Velosolex Parts for Sale: https://velosolex4600.over-blog.com/2021/02/velosolex-solex-parts-for-sale.html
Velosolex Solex video channels:
Velosolex Solex video channel: https://rumble.com/c/velosolex
(videos of various Velosolex Solex bikes, events, Bastille Day Rendezvous Rallies, and more.)
Velosolex Solex HELP video channel: https://rumble.com/c/solex
("How to" videos to help you service and understand your Velosolex Solex.)