stupid question about the crank and rods

[89SEAPOO]

Since this is a two cycle engine and there is no crankcase oil how do the rod bearings/bushings (whichever they are) keep from heating up and seizing? What lubes them? Do they have sealed bearings like on a pulley on a car or something? Laugh if you must but I don't know a whole lot about 2 cycles, and I'm here to learn so that some day I can answer other another newbies stupid questions.

 

[kustomkarl]

With all 2 stroke engines the oil is injected or pre-mixed with the fuel. The oil and fuel mixed, is sent to the crank from the intake area of carburetor and is sucked to the bottom of the crank, as the piston rises to the top of the cylinder. It is than sucked up to the top or the cylinder as the piston drops to the bottom of the cylinder via transfer ports in the sides of the cylinder. Now the mixture is compressed and the spark plug ignites the mixture to force the piston down allow the gas out the exhaust ports to the exhaust pipe. The engine completes this procedure in 2 strokes bringing in fuel and transferring to the top of the cylinder and firing it to only expels it out the exhaust. This is just a quick idea of how the fuel with oil lubes the bottom end,(crank) and allows the engine to burn the mixture to keep it running. I hope this explains it a bit for you .

Karl

 

[seadoosnipe]

bearings.......

The bearings in a 2 cycle engine are of roller ball and needle pin type. The standard babbitted bearing would not last in a 2 stroker, the friction would be to great and over heat it. The wrist pin and connecting rod bearings are needle pin and the main bearings are roller.

That's why the oil is able to lubricate and keep these motors running.

In a 4 stroke, you have an oil pump and sump, that applies pressure to the oiling system that delivers oil to the bearings babbitt through internal porting. A thin film of oil is between the bearing and metal shaft to minimize contact with the metal components, giving heat caused by friction a way of transferring away from the bearings surfaces...........:cheers:

 

[89SEAPOO]

Thanks for clearing that up for me snipe and karl. One more question for ya. Can I purchase just the lower rod bearings? My 92 XP that i purchased already has the engine apart with the cylinder jugs off and the crank and rods exposed. I can spin it over by hand no prob but one of the rods is just bouncing around on the crank and the other one is perfectly tight. The piston that was on the bad rod is also a little beat up at the top and the part above the top ring is smashed down onto the top ring and it no longer moves freely. If I was able to get a used piston with rings and matched cylinder jug and one new/used rod or bearings would I be good to go? I am trying to be as cheap as possible here and I understand it is not the correct way at all to fix this, just the absolute cheapest. I do have a 12 ton press in my shed to use if that is how these cranks are put together.