There is no issue with the standard wrist pin bearing. In fact it is a much more durable method of operation from my experience doing heavy haul, where the engine experiences high temperatures, and high mechanical load.
This theory has been put to the test, because i reused a wrist pin bearing consecutively in 4 engines, just to see how long it would last. That wrist pin bearing is in the engine currently installed in my bike, and it's operated perfectly well for over 20,000 kilometers or 12,400 miles, and is still giving dependable reliability.
By account, the engines that i have had with a bushed bearing system did not last anywhere near that distance. In fact the bushed bearing was the greatest source of wear in the engine.
What does destroy the big end connecting rod bearing and wrist pin bearing is over revving the engine.
The 2-stroke Chinese bicycle engine should not be revved more than 4,200 rpm between gear shifts, and should not be revved any more than a maximum speed of 4,800 rpm. Once you rev the engine over 4,800 rpm for any length of time, you are significantly reducing the life of the big end connecting rod bearing. If you go to 5,500 rpm, start counting the days before the big end connecting rod bearing fails.
My experience has consistently shown that normal gear change points should be made no higher than 3,800 rpm for reliable engine operation and a life span of 6,000 kilometers or 3,700 miles, though i have had one bottom end give 10,000 kilometers, or 6,000 miles or operation, but cylinders generally last 4,000 kilometers or 2,500 miles using air cooled specification 2-stroke engine oil at 25:1, together with the jetting optimised for best combustion.
