440ex oil return problem

[4door5g]

hi i have a problem with my 400ex its a 2005. the motor has just been rebuilt. my problem is the oil will not return to the tank. it fill the motor with all the oil but wont put any of it back. so it dumping out the breather in back(copper looking pipe) i have pulled the oil pump out and it seems to look ok. and the motors fresh and built right, plus no mater how long you wait theres never oil in the tank. any one had this happen to them please help.

[QuadManiac]

Check for plugged oil cooler or return lines.

[4door5g]

i took them both off and blew threw them with the air hose, oil came out of both lines so im purty sure there not cloged.

[QuadManiac]

At the wrong end of flow for your symptoms, I think, but have you checked the filter screen in the oil tank?

[4door5g]

no, how do i check that?

[drew416ex]

Originally posted by QuadManiac
At the wrong end of flow for your symptoms, I think, but have you checked the filter screen in the oil tank?

You take the clutch cover off and in the bottom of the case there is a screen close to the oil pump with one bolt holding it in.

[4door5g]

ya my mechanic had the oil pump out to check it. im sure he checked that to, hes going to put a diffrent oil pump on this week and see if maybe thats it

[BigBore24]

I think what quadmaniac may be talking bout is actually the screen that is inside the oil tank itself. you take the bottom line off your tank then screw the fitting out of the tank and there is a screen made onto it. but i think he is also right about this being the wrong symptoms for this, if the screen was stopped up no oil would be going from the tank to the motor not vice versa. you said you checked the lines for being clogged but what about the cooler itself? the only other thing i can think is the pump is just to weak to pump the oil up to the cooler.

[QuadManiac]

Exactly, BigBore. Thanks for clarifying!

BTW, I'm not familiar with the 400's oil pump, never had to deal with it yet (knock on wood). However, my Raptor has a 2 stage pump. One stage pulls oil from the very small pan beneath the tranny, the other pumps to the tank. If the ex has a similar arrangement, it could well be the tank stage of the pump that is failing. I'll look it up.

[QuadManiac]

Bingo! According to the manual, the 400ex has a two impeller pump, so one may have failed, or if you have a clog in the passage or in the supply lines to the tank, or in the cooler, it may well come out the overflow, while the other pump keeps the engine lubricated.

[4door5g]

how would i go about checking something like that?

[QuadManiac]

Disconnect the return line at the engine, crank engine over with kill switch at kill (so engine won't start, just crank), see if oil comes out of engine. If so, disconnect return line at tank, crank same way. If no oil you have a blockage in lines or cooler.

[4door5g]

so i put the new oil pump in, and its still doing it. i have no idea what to do from here. have u heard of the big bores causeing to much crank case pressure? or of any one adding another crank case breather to fix it?

[QuadManiac]

Did you perform the flow checks described earlier?

[4door5g]

yes i had turned it over when i blew threw it with the air hose. and it spit oil out of both lines

[4door5g]

any one else got any ideas? this bike just got out of the shop for a full rebuild, i dont understand what could be causen it

[4door5g]

come on some one has to have a idea this thing is driving me crazy im ready to burn the stupped thing

[BigBore24]

I dont know if its even possible or not but check to make sure the lines didnt get crossed somehow going into the engine side cover. make sure the bottom line comes out of the bottom of the oil tank. I have never heard of big bores causing too much crank pressure before, and with a brand new rebuild (im assuming new rings and freshly honed cylinder) too much crank pressure definately shouldnt be a problem. if there isnt a problem with the lines and with all the other things you have already checked chances are it is something internal. possibly the builders got a oil passage blocked or something. i would take it to them and make them fix it since it wasnt like that before.