Best premix ratio for dt125r ?

  • Hi all, I've had my oil pump in my dtr125 fail on my twice now so I've decided to completely do away with the oil pump and was wondering what the best oil to fuel ratio is? I've never done it this way always relied on the oil pump so might be a silly question lol! My bikes pretty standard only cosmetic mods like SM'd with DTX parts really and recently I fitted a full dep exhaust system and re-jetted the carb but engine wise it's nothing fancy so just in need of the best ratio if anyone can help as googles giving me alsorts! Thanks and great forum

  • There are lots of factors to consider, and I've never used Pre-Mix with the original TM28SS carb. But I started 31:1 - and 28:1. I'd say try 30:1 and go leaner if your not happy

  • Ok thanks I'll give that a try! 🙂

  • The ratios should be on the bottle of oil you buy. I ran 200mls to a full tank. But as you can imagine. Not empty the tank after eaxh stop means you get more and more oil. Yeah she smokes a fair ol whack!

  • Ah ok haha never thought to check the oil bottle for ratios etc.. glad I posted though as I now have a better idea of what I'm doing 🙂 . Can I ask one last question is there any downsides to mixing the fuel yourself (apart from it being quite inconvenient lol) will it damage the engine in anyway after a long period of time doing it or is it ok long term?. Thanks

  • Yep there are some down sides.

    Imagine this. You are cruising down yhe dual carrige way. Engine at 8K rpm. Now usually the oil pump is driven off the crank shaft. So 8 thousand rpm spins the oil pump 8 thousand rpm. The oil pump is also controlled by the throttle cable.

    Now remove yhe pump. The oil only enters the engine via the fuel. Yhe engine is spinning 8 thousand times a minute. But you are cruising. Not accelerating. The throttle is cracked open just enough to maintain rpm. You then shut thw throttle off as you are approaching then. The engine slowly winds down. From 8. To 6 to 4. You shift down. 8 6 4. Shift down 8 6 4. Again and again from 6 to first.

    Not only do you ride along the dual carrige way at 8k with oil delivery at the minimum. You then shift down 5 gears with no oil pump.

    The eventuality...engine seizure.

    The point I am trying to make is that you must learn to ride a two stroke. I done it oil pump no oil pump. But I remember initially doinh it I struggled. Two strokes don't like engine braking because you go from low rpm to higg rpm and starve oil. Unlike a four stroke when the oil pump picjs up oil.

    The premix two stroke only gets oil when the throttle slide opens. So be sure to blip the throttle upon down shifts. And be sure to wide open throttle for very short periods of time wheb maintaining a cruise as to ensure good lubrication of oil into the engine.

  • Thanks! very informative reply there I've never thought about it like! Yeah looks like I'll be riding differently now I'm mixing the fuel defo wouldn't want the engine seizing again happened before due to this oil pump so this seems the only way to go

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