I ride my Magnum a lot in Michigan during ice fishing season and often make longer runs in snow across frozen lakes. The other day I was unloading my machine from the trailer and noticed that engine oil (about 2 ounces) had leaked onto the bed of the trailer from directly under the crankcase toward the right side (shift lever side) of the ATV. Looking underneath the ATV, I could see a few more drops of oil hanging onto the skid plate in that area. Since it didn't look that serious, I decided to go out on the lake as usual. I monitored the leak throughout the day whenever I stopped to fish and saw a few more drops fall on the ice/snow from that area. At the end of the day I loaded the ATV back on the trailer and head for home. This morning I planned to have a closer look at the leak. When I looked underneath the ATV on the trailer I was surprised to see that the oil leak has apparently stopped. Not even a drop on the trailer bed or any drops hanging from the skid plate. I checked the engine oil level with the dipstick in the oil tank and it is filled. I don't want to tear into this thing if I don't have to so thought I'd ask for opinions here. Is it possible that oil may have temporarily come out of a crankcase vent and has now stopped? Is this normal? Any thought ideas would be appreciated. Thanks.

 

Someone might have a better idea on what or where it's coming from, but have you checked the air box and the crank case vent line?

 

Check your vent lines(2 on the Magnum) from from the oil tank and crank case vent that go to the air box as Scooter recommended plus run your finger under the water pump cavity at the weep hole and see if you have a film of oil. Oil could possibly seep or forced from the internal oil seal and drip out the weep hole. Another place to check is the recoil housing. Same thing can happen on the stator plate o-ring when temp is cold and if o-ring needs replacing, oil can seep around it.May just happen in cold temps,but I'd run light weight oil like 0w40 and keep a check on it.If it was a combination of oil/water I'd say water got into the recoil housing.

 

Thanks guys. I will check on all of those things. It has been very cold this winter so maybe the vent lines did get some frozen condensation in them. I know there was a oil tank vent line but did not know there was a crankcase vent line.

 

Can't remember off hand how it splits,but vent ties in under the air box,drain tube is at the back of the air box for any excess oil removal. Dirt Cheap Yamaha, Polaris, Suzuki & Kawasaki OEM Parts & Accessories – Cycle Parts Warehouse