to answer your question my sons derbi senda r does 55mph with me on it and im 14stone but remember it is unrestricted and if you upgrade to a 70 or 80cc kit it will go even faster
there is a restrictor in the carb try tht
stop what your are doing and sell it to me.
Should be just after the postive output from the battery, fuse is a 4amp and should be just a couplr of inches from the battery
about 80 mph
Its 19 to 22 newton meters on a torque wrench. It should say in the manual under section 'torques'.
When you do the exhaust, it means there's the potential for more exhaust fumes to leave the engine, but to keep the engine 'balanced' you therefore have to increase the amount of air (by an air filter) AND fuel (by a bigger jet in the carb), which will result in a more powerful engine. The sprocket can then be changed to alter the gearing to improve either acceleration or top speed, at the loss of the other. mate
Derbi was created in 1922.
It may be your stator, coil or even your spark plug give these a go if your stator isn't giving enough power it won't give the electrical charge to your coil Try this it may be the problem
The motto of Derbi is 'Mucho + k Moto'.
a 50cc bike is about 10mph for adults and 35mph for kids under 10 for 12 upwards its about 25mphslow
About 5km/h
45mph with no mods