When the bike is at operating temperature the oil is the same viscosity. the first number representst he viscosity at room temperatures.20/40 wight oil is recommended.Maybe 10/40 is too light?
Is the oil plug still there?
No I meant too tight, but I said it wrong earlier. Jumping a tooth is normally too loose, worn belt or gears.BradT ..... don't you mean if its too loose, ?