2 stroke questions



  • Hi all,

    So I know the basics of 2 stroke engines and I know the crank is oiled by the stroke oil.

    My yz engine doesn't have an oil pump and it's self mix.

    I'm assuming not all 2 stroke road bikes have always had a oil pump?

    The reason I ask is because a guy I was talking to today reckoned I would be in trouble using the yz engine on the road because it would have a lot of overrun/coasting down hills and in traffic etc. He seemed to think that it would blow up rather quick as the crank would be dry.

    I know some oil will get onto the crank with the idle ammout that's aloud to pass but will this be a problem?

    Also what ratio would you guys use on the road? I don't mind a bit of Smoke and I also get a bit excited with the throttle.... every day.

    Thoughts would be great


  • Global Moderator

    As @Calum has mentioned a few times, if you want to give the bottom end a nice bit of oil every now and then, just hold the clutch in and twist the throttle. When they are on the track, 2 stroke bikes are pinned 90% of the time so they are designed to work like that, but then they are probably rebuilt after every race. I never had any issues with my SX 125 and I treated it like a normal bike. Didn't rev the nuts off it all the time but didn't coast everywhere either.



  • It's the converse.

    He is right, you will seize the engine coasting downhill.

    However this is worse on oil pump bikes. Not premix.

    The oil pump on the DT runs off the throttle cable. No throttle no oil, or very little. This isn't true for all bikes. On the aprilia the oil pump is driven directly from the crank. So it's relative to the rpm.

    As said, the best way to keep the engine lubed, it's more than the crank, blip the throttle. You will find on a crosser it will foul the plugs as they are designed to be flat out all the time. Riding them on the road without caining them will foul the plugs.

    The crank actually survives on very little oil. It's the cylinder walls and rings that require the modt amount of oil.



  • Ok awesome thanks guys



  • What ratio would you run?



  • 200mls to a full tank. 0.2l to 10l.

    Smoked like fook mind you, it was fine when you were thrashing the tits off it. But to be honest I used my bike as a daily and never thrashed it.

    It may sound like a waste, but it's so dangerous commuting on a motorbike. The amount of times I nearly got knocked off was crazy. Plus I really loved going slow on my bike. It was just built for cruising it is lush.



  • I like 34:1 or 32:1 if your romping it, it's a shame the gear ratios are so short on a YZ. If you keep it fuelled on the over run, just a blip or 2, you can expect no issues, provided the engine has the correct fuelling mixture!

    These engines are awesome, and can withstand abuse, just got to keep it setup correctly.