4-stroke engines can be ringed or non-ringed like two strokes, they can also have dual needle or air bled carburators. I don't know of any 4-strokes currently being sold that have bushings instead of ball-bearings. Most of the popular 4-strokes sold today are ringed and have dual needle carburators.

Bushing engines aren't inherently weaker or shorter lasting than their ball-bearing counterparts. The O.S. .65 LA is much lighter weight than the O.S. .61 FX, but will actually turn some props faster than the .61 FX using the same fuel and glow plug. Thunder Tiger's published specifications show that their GP-61 produces more horsepower than their Pro .61 ball-bearing engine.

Bushing engines get a bad rap for two reasons:

1) The O.S. .40 LA is by far the most commonly sold bushing engine in existence, and it is weak compared to all other .40-sized 2-strokes. The Thunder Tiger GP-42, for example, is a bushing engine with an air bleed carburator just like the O.S. .40 LA, but is signficantly more powerful. Too many modellers think that the .40 LA is representative of the power output of all bushing engines, and this simply ain't so.

2) Bushing engines are designed to run pure castor oil lubrication. The ideal fuel for an O.S. LA series or Thunder Tiger GP series engine is 10% or 15% nitro with 20% pure castor for lubrication. The castor oil not only helps "float" the crank shaft inside of the bushing, but the extra thick viscosity of the castor oil also helps seal up the crank case and provides maximum compression for the engine's operation. Too many folks are buying all synthetic or 80% synthetic/20% castor lubrication fuel to fly their bushing engines. It's getting difficult to find all castor lubrication fuel anymore.

If you run any bushing engine with 20% lubrication all-castor fuel, you'll be pleasantly surprised by the performance. This type of engine will also last long enough to pass on to your kids someday so long as it is tuned properly and not dive-bombed into concrete.