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  1. #1

    What happens to excess oil, water, gas, etc. that ends up in crankcase?

    If oil has been sprayed on the crank and rods, fogging oil in cylinders, or "God forbid" water has accidentally gotten into crankcase because of bad flushing techniques.
    Does it stay in the crankcase forever, or does heat and steam evaporate it and send it on through?
    I also had a jetski mechanic tell me that if you run the ski in sand or muddy conditions, you can suck this up and decrease the cooling capacity of the engine because it settles out and stays in the engine. Any truth to this? Wonder where it accumulates?


  2. #2
    Waveruiner pauladave's Avatar
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    Have a look at 'How a 2 stroke works', and you'll see that the crankcase and crank are subjected to a constant 'wash' with 2 stroke mixture during operation (unlike a 4 stroke which relies on seperate oil in the sump or remote tank to be pumped around the engine parts, and not burned but re-used thousands of times before being changed at regular intervals). This is why a 2 stroke MUST have a pressure test on rebuild, as any pressure loss in the crankcase will result in the engine not running right, and can lead to a very disastrous 'lean siezure' etc. Any fogging oil etc. in the crankcase is thus mixed with the gas/oil mix and burned off on the ignition cycle. Hence a ton of smoke when you de-winterize a 'fogged' engine, as it's burning 2 stroke mix AND the fogging oil until it's clear. Water is the same, in small quantites, and will be carried out of the motor with the exhaust, so long as it's not enough to render the gas mix unburnable! You will read of motors being totally flooded with salt water (as mine was 3 years ago), but being saved by IMMEDIATE removal of the water through the plug holes, the engine being started, and then being run at full throttle for a good 20 minutes on the water (the best advice I ever read was, "Ride it like you stole it". I did and it worked!). This gets the 2 stroke mix to wash the crankcase and cylinders clean of any water and salt, so preventing damage from rust to the crank bearings and journals etc. Of course, I recomend you don't fill the engine with salt water at all, but mine didn't cut-out when I dumped it after a big wave, and it sucked a gallon in before finally dying! Your mechanic was also right in saying mud and sand can cause the cooling water passages to clog, but a good flush (10 minutes) on a clean cold water hose after EVERY ride should help prevent this. Never use warm or hot water as this crystalises the salt, and it becomes as hard as rock inside the passages! Obviously try to avoid getting in too close to any sand or mud banks etc, as this not only gets into the water passages, but it ruins impellors and pump liners as well. Hope this helps. Dave.

  3. #3
    Wow, quite a dissertation! I never expected such an involved response. Thank you.

  4. #4
    Quote Originally Posted by pauladave View Post
    Have a look at 'How a 2 stroke works', and you'll see that the crankcase and crank are subjected to a constant 'wash' with 2 stroke mixture during operation (unlike a 4 stroke which relies on seperate oil in the sump or remote tank to be pumped around the engine parts, and not burned but re-used thousands of times before being changed at regular intervals). This is why a 2 stroke MUST have a pressure test on rebuild, as any pressure loss in the crankcase will result in the engine not running right, and can lead to a very disastrous 'lean siezure' etc. Any fogging oil etc. in the crankcase is thus mixed with the gas/oil mix and burned off on the ignition cycle. Hence a ton of smoke when you de-winterize a 'fogged' engine, as it's burning 2 stroke mix AND the fogging oil until it's clear. Water is the same, in small quantites, and will be carried out of the motor with the exhaust, so long as it's not enough to render the gas mix unburnable! You will read of motors being totally flooded with salt water (as mine was 3 years ago), but being saved by IMMEDIATE removal of the water through the plug holes, the engine being started, and then being run at full throttle for a good 20 minutes on the water (the best advice I ever read was, "Ride it like you stole it". I did and it worked!). This gets the 2 stroke mix to wash the crankcase and cylinders clean of any water and salt, so preventing damage from rust to the crank bearings and journals etc. Of course, I recomend you don't fill the engine with salt water at all, but mine didn't cut-out when I dumped it after a big wave, and it sucked a gallon in before finally dying! Your mechanic was also right in saying mud and sand can cause the cooling water passages to clog, but a good flush (10 minutes) on a clean cold water hose after EVERY ride should help prevent this. Never use warm or hot water as this crystalises the salt, and it becomes as hard as rock inside the passages! Obviously try to avoid getting in too close to any sand or mud banks etc, as this not only gets into the water passages, but it ruins impellors and pump liners as well. Hope this helps. Dave.
    well said, i sunk my old 800, and never had any problems after i brought it back to life. 2 strokes are amazing machines, especially once you research the supercharging effect of the exhaust and how it creates the powerband. fascinating stuff

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