ok here is the deal a customer brought in a 2001 250 polaris that would not start it had low compression. i pulled the cylinder off and had the machine shop bore the cylinder reinstalled it and it will not start? has good compression i checked the piston before i put it in. it seems it is sucking at the exhaust side and spitting on the intake side. i used a namura piston the f mark to the flywheel. i also installed new bottom end seals.

 

try a leak down to see if there are any vacuum leaks

 

done that no leaks it is blowing air out the intake sucking on the exhaust

 

its going to do both blowing and sucking on both the intake and exhaust. since there are no mechanical valves to stop the wrong action, it will do whatever the piston is trying to do till the skirts block off the appropriate port in tthe jug

 

SOunds like you have the piston in wrong.Most pistons are marked to go to the exhaust.

 

numara pistons have a f that goes to the flywheel side. he put it in right

 

<div class="FTQUOTE"><begin quote>Originally posted by: ftwflh

SOunds like you have the piston in wrong.Most pistons are marked to go to the exhaust.</end quote></div>

yep your right...