250ED Thunderdog oil pump

[dnaj11]

I recently purchased a very nice Thunderdog, alas the previous owner had changed the throttle assembly with a straight single pull Magura type and disconnected the oil pump. He ran premix for several hundred miles with the disconnected oil pump still in the motor. I'm guessing this was no good for the oil pump should I wish to reconnect it? I'm also guessing I'll have to split the cases to inspect it. Can anyone advise? Will the process and pump be the same for the 250SL -searching for a manual. Thanks

[olddogs]

These pumps are pretty tough. You do not have to split the cases to check its function. Leave the bike in neutral and remove the shift cover and pump cover plate. Hook up the supply hose from the oil tank or some other source and let it drip to remove the air. Then hook it to the inlet side of the pump and start the engine. You already have pre mix in the gas tank. You can manually rotate the pump control to full speed and wait for it to start pumping out the output side. These do not squirt oil across the room. They are a very slow pulse of one drop at a time. Rotating the arm to full will speed the process. If the pump works just locate a throttle assembly and cable. Their is a little barrel end that holds the cable in the pump arm. Adjust as needed. the 250 SL and ED systems are identical.

[dnaj11]

Looks like I actually have everything to restore the oil injection circuit. ,The PO gave me a box of parts with everything nicely labeled - including the oil tank and fittings but as I inspect the bike further, the PO cut off the fill spout part which is welded to the frame - where you put the two-stroke oil in. I don't know why he did this. Bike has a reproduction Clark tank but that's no problem.

So I'm wondering if I should just leave it all as is and continue to run pre-mix. I can pull the oil pump to save it.My first rule of old bikes is -do no harm! Do they make a backing plate for it? Will I even need a backing plate if I pull the pump?

[olddogs]

The oil injection system made it convenient for long trips where you would be stopping for fuel while headed for your destination. Just gas it at the pump and go. It is not as much of an issue on a dirt bike that usually returns to its starting point before it needs gas. I think someone made an accessory block off plate, but I'm not sure if its still available. A gasket and any flat piece of thin plate steel or aluminum with 2 holes in the right spot should work. Use the pump to locate the position of the screw holes. It is not visible so making it the exact shape of the old pump is not must. A very common modification.