my speedfight 50cc would not start so i took the carb off and cleaned it, i fed petrol straight into the engine bypassing the carb and it started but when i came back the next morning, no luck. I read on the internet that a 100cc carb would fit and possibly increase the performance so i bought one and fitted it and i got it started once but if i gave it some revs it cuts out please help.

Alex Birch, March 2010

sorry but you wasted your money, 100cc's are dell orto and 50 ccs are gurtners with different reeds inlet manifolds etc, doesnt work your problem would almost certainly have been the autochoke (solenoid) invest in one of these!

m, March 2010

i expect it is too rich,the 100 cc carb runs a bigger main jet then the 50cc one,did it tick over ok before you revved it ?and have you checled the reed petals in the reed valve are not shattered or split as this will also cause this problem as will a leaking crank seal

adam bike doctor, March 2010