chainsaw-weedeater motors
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More Turbo
Joined: Jun 2001
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chainsaw-weedeater motors
I never really thought about this much untill I tore into mine. on a 2-cylce engine such as a chainsaw or weedeater, how does the bottom end(crank-rod bearings) get lubricated? there is no oil down there. Or there isn't in any of the ones i've seen :P
Post Fiend
Joined: Feb 2000
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From: Kansas
chainsaw-weedeater motors
[updated:LAST EDITED ON 16-Jan-02 AT 06:12 PM (EST)]As the piston goes past the intake port fuel mix still flows and thus goes to the crank area. The reason you may not have seen any lubrication is most of the mix is gas and has evaported off or was burned. There is still a film of oil present. Not much but it's there.
If you could see a 3D image of a 2 stoke motor in motion it would be clearer. There is a reason for the size and shape of the ports on the cylinder wall.
There is never much lub down in the crank area - rather a film of mix on the surfaces while the motor is running.
If you could see a 3D image of a 2 stoke motor in motion it would be clearer. There is a reason for the size and shape of the ports on the cylinder wall.
There is never much lub down in the crank area - rather a film of mix on the surfaces while the motor is running.
Fleet Owner
Joined: Aug 2001
Posts: 29,941
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From: Drummonds, TN USA
chainsaw-weedeater motors
Two-Cycle engines carry the lubricant in the fuel-Air charge itself. This is why they are so "smoky"....
It's also why the plugs foul so often.
The bottom end acts like a compressor, and pushes the recieved fuel into the cylinder through a bypass that is uncovered as the piston travels down...
The reason you have a specific mix that is needed for your engine is because the manufacturer has to balance what a "burnable" mixture should be, against the lubrication of the lower end bearings (usually ball, or roller bearings).
Another point worth mentioning, is that if a 2-cycle is left unused for too long, the oil in the bottom of it can become "gummy", and not work so well.
For this reason, you should be careful when you store one for a long time. Sometimes it helps to ground the plug, and spray WD-40 into the carb, then pull it through a few times to clean it out.
-Hope I helped some...
~Wolf
It's also why the plugs foul so often.
The bottom end acts like a compressor, and pushes the recieved fuel into the cylinder through a bypass that is uncovered as the piston travels down...
The reason you have a specific mix that is needed for your engine is because the manufacturer has to balance what a "burnable" mixture should be, against the lubrication of the lower end bearings (usually ball, or roller bearings).
Another point worth mentioning, is that if a 2-cycle is left unused for too long, the oil in the bottom of it can become "gummy", and not work so well.
For this reason, you should be careful when you store one for a long time. Sometimes it helps to ground the plug, and spray WD-40 into the carb, then pull it through a few times to clean it out.
-Hope I helped some...
~Wolf
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