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2 stroke "autolube" oil pump leaking?????

Discussion in 'Technical and Troubleshooting Torque' started by yamahapat, Aug 7, 2005.

  1. I've got a 1999 Yamaha DT230 road/trail 2 stroke that has developed a leak from the autolube pump area. It is a single cylinder that uses a separate oil tank and automatically pumps oil into the motor so you dont have to premix the fuel. I am using the recommended yamaha oil.

    Ive had the bike for about 3 months and have done about 2500 k's since I bought it at 9000k's. It hasnt missed a beat in the past and has seen a fair bit of dirt but is mainly used on the road.

    Just recently I have noticed small pools of 2 stroke oil under the bike when it is parked and it is coming from the drainage hole in the pump housing. When I remove the pump cover there is a bit of oil sitting in the casing, only about 15mls, but I can't see where it is coming from. I clean out the pump housing, start the bike, warm it up and watch the pump and can not see any leak. Took it for a ride, came home and still no oil in the casing. Left it overnight and the next morning the pools of oil were back. It has also fouled up the plug a few times recently, so badly that the bike wouldnt start. Ive had a few people look at it but no one can pinpoint the problem and Yamaha Australia do not have a service manual available for this bike.

    It has only started happening since the cold weather hit. Its been about 3-4 degrees the last few weeks at night and the bike is left outside under a carport.

    Any help would be greatly appreciated because im completely stumped now.


  2. The fact that it only seems to happen when the bike is left for an extended period (overnight or longer) indicates that it is a very small leak that will be hard to find.

    You didn't say what side of the bike the pump is on either. If the bike leans in the same direction on the sidestand that could be an issue too. Oil will obviously find its way to the lowest point.
  3. Have you considered disabling the oil pump and just using premix?

    It could be that the lines that combine the oil/fuel mixture are clogged forcing the oil to the drainage hole, and also doing damage to the bike by not supplying enough lube to the motor.

    Just a thought. I had the same problem with a GT250 stroker a few years back, ended up snapping the con rod and blowing the piston through the exhaust. Not fun at 100mph!!
  4. Excellent suggestion, even if you just do this as a trouble-shooting exercise. If it stops the problem, you'll know the source of it and you can fix it. Great stuff, foxy!
  5. I'd say there's probably a problem with the seals inside the oil pump or the oil pump may need adjusting.

    The oil pump flow is usually regulated in conjunction with throttle action. As the throttle is opened the pump pushes out more oil. If when you are closing the throttle the pump isnt returning to the closed position and it is remaining slightly open oil will continue to drain from the oil reservoir.. its only point of escape being the breather hole it sounds like its weeping from
  6. Thanks for the replies.......

    I might just disable it for now and run premix fuel. I think it might be a sign that its time to upgrade.