i just recently bought a 400ex and now it is having problems. it will stay running with the choke a little under full choke but anywhere else it shoots smoke from between where the engine is connected to the carb.. at first i thought it was the carb then i cleaned it and it still doesnt work. if anyone has any ideas on what to do please let me know. thanks

 

hmmm, you mean it shoots smoke from the boot attached to the engine? or is it comming through the airbox? there should be nothing coming from between the carb and engine. This area should be airtight. from the situation with the choke that would say that it is too lean, and i would clean the carb. Make sure enough clean gas is getting to the carb, also i would replace the spark plug, and check the valves probably.

 

when it starts it runs and then when it stahls out the boot pops off the engine and then it dies. it pops a little cloud of smoke out of it and it seems like the exhaust gets built up and the back pressure pops out of the boot.

 

i would say either ur jetting is very lean or u got a funky intake valve

 

could be the timing chain jumped a tooth or 2 , then backfires and blows the carb of the boot ?