My DT3 has had some 2stroke oil pooling in the magneto side case. Not much and it's not getting on any of the electrical stuff but some collects in there, at the rear of the case.. Can't figure out how that oil could be getting in there. It's not transmission oil, it's same color as the 2 stroke oil in the oil tank. Any ideas? Thanks, Al

shouldn't be able to happen in theory. Not something unusual like the carb bowl breather/overflow is being vented into there via 'it's' breather pipe & fuel is dribbling in then evaporating leaving the oil residue. Ok i just shot my own theory to bits as oil pump feeds into the inlet not carb--well unless it's premix. Ignore all that sorry, stupid theory. Still want to know though!!

Its time to play detective.....my bet is the crank seal is leaking on that side.
Second cause is oil is leaking from one of the case screws (highly unlikely)
inside that cover.

Pull the flywheel and remove the stator ...clean the case till its absolutely clean of any oil...reassemble and ride for a few miles.

Tear it back apart and look real closely.....the oil trail should be evident. If not you need to use a magnifying glass !

If the oil pump is allowing oil to pass through while it is sitting and the check valve spring is missing, weak or stuck and the hose to the banjo bolt is cracked or loose or the banjo bolt gaskets are bad then 2 stroke oil may be leaking across the top of the crankcases through the grommet around the wires into the magneto case.

Also oil can pass through into the cylinder without leaking outside the engine. It can fill the crankcase to the point of it leaking past the left crankshaft seal into the magneto. This would also result in more smoke when starting.

Lots of ifs in this scenario.

Thanks for the input guys - will do some more sleuthing and report back when i get it figured out. stay tuned!
There seems to be an odd little sump in the left case and cover - photo attached - Guess they must have planned for fluids to get in there, but wouldn't hold much. Al

Replace the magneto side crank oil seal.

After removing the points plate on my 74 dt250, I noticed oil leaking from the case screw , took a metric allenwrench to see how tight it was , it was fairly tight but I was able to loosen it , I tightened it back up and gave it a little extra and the leak stopped.

Would anyone know the tork spec for the Allen case screws

Not sure there's a torque spec but probably is. I just do em up tight. If ya worried perhaps get a very small thin Oring that can be compressed in around the screw without cutting the Oring--just as a security blanket. Only way oil can get up there is from the case joints which is a worry but--wouldn't worry if she's running ok. More trouble than its worth to get in there for that.

Had the same issue as you're describing, just a small drip of oil on one of the case screws behind the stator. Once I removed the stator I could see some oil on the crank seal behind it. I replaced that seal, cleaned everything up and put it all back together; no more leaking.