motocross bike

[willyh..]

hi im new to this and looking for some help not sure if im posting this in wright place
iv got a kx 125 was rideing fine then next day went to start it and it had no compression so I put new piston and ring in it but still the same can anyone help me as im new to the motocross this
thanks

 

[Rich Rohrich]

When you say it has no compression did you actually measure the compression before and after you replaced the piston?

 

[The Redrider]

If you have no compression, it sounds like something is severely worn. Your cylinder could be worn out, may be time for a replate for nic, re-sleeve for regular cylinders. You will have to match the piston to the new bore. Did you install your rebuilt piston correctly? Arrow to the front? Rings in correctly, wrist pin circlips locking correctly? Did you torque the cylinder base and head to specs? Spark plug installed correctly? Lots of factors, but rebuilding a single cylinder is very easy with the manual, you have a shop manual right? Hmmkay...

 

[jaguar]

Could be losing compression past the head gasket, especially if you didnt install a new one. Also could be a warped head.