Two Stroke Rear Bearings
04-13-2009, 06:00 PM
#1
Two Stroke Rear Bearings
There has been a lot of talk lately about replacing the bearings in OS two strokes. I have a 120AX, and have been advised to use a sealed, stainless steel bearing. I have also heard conflicting advise saying that a sealed bearing will rob the rotary valve of lubrication.
Can someone please explain the pro's and con's of using a sealed bearing, and maybe talk about how lubrication reaches the different parts of the engine? (I find it hard to believe the rotary valve will suffer as all of the engine's lubrication comes from injected fuel, which obviously comes directly in contact with the valve.)
Can someone please explain the pro's and con's of using a sealed bearing, and maybe talk about how lubrication reaches the different parts of the engine? (I find it hard to believe the rotary valve will suffer as all of the engine's lubrication comes from injected fuel, which obviously comes directly in contact with the valve.)
04-14-2009, 09:50 AM
#2
My Feedback: (11)
RE: Two Stroke Rear Bearings
You replace bearings only if you have a good reason. If they are clean and smooth, there's no reason to replace them. There are a lot of different suggestions, but the best one is to use a stock bearing or equivalent. We only use bearings provided by O.S. to replace bearings that need it. There are no "sealed" bearings in use in O.S. engines. Some come with grease packed between the shields, but that grease will eventually become washed-out by the action of model fuel. This would happen after several seasons of average use. Only certain engine have such a bearing, and they are not two-stroke, high-speed engines.
You don't want to replace an open bearing with a "sealed" bearing because the bearing will get no lubrication. That will drastically shorten the life of your engine.
The best thing is to use a good-quality fuel with a good lubricant package. Fuel with a significant amount of castor oil in the oil mix is highly-recommended because castor does a better job of corrosion prevention than the synthetic oils, and it also provides better protection against high heat damage. After each day's flying, run the engine dry of fuel (at idle), and then crank it until it will no longer fire. Finally, you must be very liberal in the application of an after-run product. The interior of the engine, and all the steel parts must be well coated with the oil. A few drops is less than useless. We use a teaspoon or more, depending upon the size of the engine.
You don't want to replace an open bearing with a "sealed" bearing because the bearing will get no lubrication. That will drastically shorten the life of your engine.
The best thing is to use a good-quality fuel with a good lubricant package. Fuel with a significant amount of castor oil in the oil mix is highly-recommended because castor does a better job of corrosion prevention than the synthetic oils, and it also provides better protection against high heat damage. After each day's flying, run the engine dry of fuel (at idle), and then crank it until it will no longer fire. Finally, you must be very liberal in the application of an after-run product. The interior of the engine, and all the steel parts must be well coated with the oil. A few drops is less than useless. We use a teaspoon or more, depending upon the size of the engine.
