Re: Suzuki DT140 Oil Induction Filter
Assuming your '85 is set up close to my '98 DT140 (my service manual covers '86 to '00) here is what you should look for...
Looking at the parts breakdown, Fig. 8
http://store.brownspoint.com/pdf/DT140(83-85).pdf I don't see an oil flow sensor. I'm not so sure your alarm is associated with the oil flow because I don't think you have a sensor for that. It still may not hurt to remove the oil tank, dump and filter the oil, reinstall the tank, and BLEED THE OIL SYSTEM to remove any air.
On my model, to AIR BLEED:
1) Mix some 50:1 fuel and hook it up to your engine.
2) Fill the oil tank.
3) Start the engine and let it idle.
4) Open the small bolt (8mm on my engine) to let the oil flow out of the pump. This is very messy, use lots of rags stuffed in the engine compartment.
5) Hold the oil flow arm full open to speed the bleed process.
6) Close the bleed screw/bolt.
Mixing any TC-W3 rated oil should be fine. However, I blew my '96 DT115 because there was a clump of gelled oil in the bottom of the oil tank. I have no idea what caused the oil to gel but it was there when I dumped the oil tank. Given the year/age of your engine I think it would be a good idea to dump the oil to make sure everything is good.
If this does not fix your problem you can continue troubleshooting.
