Brand new oil pump (900 RMK) but no oil getting pumped in!

[Gmiller]

I've been having problems with my 900 oil pump after a top end rebuild, i bled it many times with no luck so i bought a new one, i confirmed that the new pump is spinning when the crankcase is moving, i bled the lines and it still didn't work, im running lean again! One other thing i noticed is when i take the oil cap off there is an air suction there (is that normal) When i bleed the lines i have to remove that cap in order for oil to run though! Otherwise i don't know what to do, i've done it all so far and i only have 1in of rope left, Please help!

Thanks
Grant Miller

 

[skibreeze]

Sounds like your oil cap vent is plugged, time for a new one. Or figure out what is wrong with the old one.

 

[nmmiles]

^^X2

 

[GKR]

You nailed it. The cap must vent to gravity feed the pump. Sounds like you did a pump change for nothing Once you draw a negative pressure in the tank the pump will starve and no worky.

 

[diamonddave]

Oil cap must be vented as stated. Was thinking about this on my last ride but forgot to find your last post.

 

[nmmiles]

Not to hyjack a thread but what about the fuel cap? Is the fuel system vented in any way? Mine is always under vacuum and can be a PITA to get the cap off if I ride on a full tank without taking it off once in a while. Sled runs fine, no lack of fuel what so ever.
Thanks,
Nolan

 

[diamonddave]

Not to hyjack a thread but what about the fuel cap? Is the fuel system vented in any way? Mine is always under vacuum and can be a PITA to get the cap off if I ride on a full tank without taking it off once in a while. Sled runs fine, no lack of fuel what so ever.
Thanks,
Nolan

Fuel tank is vented. But not the cap.

 

[rmkboxer]

oil cap, it should flow, just rebuilt my dads motor because of this. very costly

 

[benamen]

nmmiles

Your gas tank is vented near the top of the tank on the clutch side. Plastic vent hose kinks near the tank in that area and causes the vacuum. At least that is what problem I had after pulling the tank to replace the ECU.

 

[Gmiller]

Well thanks guys!! I took a look at it and tried to suck/blow on the tiny hole, but nothing seemed to work so im gonna go and say you were all right! Im gonna buy a new cap and hopefully thats what all my headaches have been about the last two months! New oil pump (preventative maintence) i guess! There is still snow, so i have a chance of fun yet!

Thanks Again
Grant