hi i have a mini dirt bike 2stroke 50cc as soon as i pull start it jumps into life and flys away from me !! the throttle isnt stuck brand new carb and air filter so have no idea what the problem could be

joe_rs_turbo, May 2010

no its only the springs that will need to be replaced mate they stop the cluth from engaging all the time and only when they are spinning enough to be thrown out with centrifugal force should they engage.the springs are about £5.00 for a set if you can get them.ve-uk sell them for scooters but they may not be the right length for a mini moto unless you can measure them and ask them if they have some that length.

adam bike doctor, May 2010

thanks guys :/ if it is the cluth will it be exspensive ?? thansk will give it ago :)

anderson_rs_turbo, May 2010

if its NOT revving to high then as ted says the centrifugal clutch is engaged which will no doubt be the fault of the clutch shoe retaining springs ,they break and cause this problem.

adam bike doctor, May 2010

sounds like the tickover's set too fast or the throttle cable's too tight, this will make the centrifugal clutch engage immediately the engine's started. Put the bike on a milk crate with back wheel off ground to adjust carb and/or cable with engine running. If that doesn't work it means the clutch is seriously binding or stuck in the engaged position and will need further investigation.

2 stroke Ted, May 2010