oil pump help

[jackrb100]

How do you check that the oil pump is working on the 400ex. I'd appreciate if someone could help me. Thanks.

[rubbersdown]

It s a mechanical pump so not much can really go wrong with it. If you want you can measure the tolerances between the inner and outer rotor, service limit is .20mm. I guess if you really want you could pull the return line and fire up the quad and watch oil squirt into a cup or somthin. What makes you think its not working? It could lose a little oil pressure after a while from wear but being a mechanical pump the only way it can really just completely stop working is if the rotor got jammed up with something (which is unlikely because of the filter screen) and/or all the teeth stripped off the oil pump drive gear which is also unlikely because you would definitely notice that as there would be 20 or so teeth bouncing around in your bottom end which would more then likely seize the motor up in more than 1 way.

[jensenracing77]

there are two oil pumps in one on the 400EX. one pumps oil to the oil cooler/tank and the other pushes oil through the engine from the tank. i don't see to many oil pumps with problems on the 400EX other than the ones that never have there oil changed. if it has wear, an entire new pump is only $80.