So my 400ex was smoking bad!! So i replaced the stock piston with a pro x piston and had it bored .50 over got all the parts back put the sleve and head and valve cover back on it turnes over just fine it either is backfiring or acting like it wants to start...So i put new plug in and does the same thing.So i pulled the plug back out and its getting spark!!! Is there anyway that the timing is 180 out??? Any input?

 

you can clean the carb, but it sounds like the timeing is off

 

timeing is off

 

I know i got the timing on put the cam with the lobes down and have the three marks lined up and im goin off the t mark!! I did notice i lost the decompression pin that rides against the cam its a $3.00 part..I am sure thats what it is!