Gears keep locking up ( i need advice)

[Rockjaw]

Just put on a 66cc 2 stroke ..the engines gears keep locking up..not a kink in the chain..the other side..i open the gear (clutch) side box and the gears turn and then i move the bike and it locks up...ive greased the gears...still same thing. Any advice ? someone have a video on solving this problem?
thanks all!
RJ

 

[crassius]

take out spark plug - lock clutch lever to release clutch - turn engine by spinning magneto nut

if it locks up now, it should be easy to spot why

 

[josh]

make sure you keep an eye on how the chain is feeding into the engine sprocket, you could have a tooth missing. id also make sure your chain tensioner is lined up with the rear wheel sprocket. and lastly give the back tire a spin and see if your sprocket spins evenly. if anything is off it could be locking the chain up. if all thats ok then you could have a ceased piston and thats usually from mixing your 2 stroke gas/oil wrong. ive had that happen to me before. thankfully i was able to free the piston after taking apart the engine. now i know its always better to have more oil than less if your not sure how to measure it