You hit the nail on the head..."cheap ass engine". In an effort to cheapen it; the factories have skipped over some important machining operations. The engines I offer will no longer be poor quality. I've been looking at these since September as far as what can be done to make them far superior without going overboard.
I figured I described enough stuff in the last post so here's more...
Looking at the core product...the castings are, (contrary to popular belief), totally acceptable. The castings are made by a process called Die casting. How do I know this: Look at the castings, they all have ejector pin tooling marks. Die casting is similar to injection molding pastic and produces a far superior product when compared to sand casting.
In creating a split case engine there must be a positive register that ensures the two halves can be assembled so that the bearing recievers are pefectly in-line and concentric to each other, especially when there are two sets of bearings; one set for the crankshaft, and another for the countershaft. A missalignment of more than .0015" is not acceptable. The factory manufacturing process allows for more than this. It's a point of bearing failure which only serves to leave the novice wondering why some engines last so much longer than others. Based on the way the case halves are registered it is purely chance as to whether or not you get a good engine or a bad one. The final alignment is not positively machined...it is left up to the "feel" of the worker who is doing the assembly.
Sealing is important for any of the mating surfaces that are part of the combustion process. The machining of these surfaces is poor from the factory, that's why they ooze from every orifice regularly. This not only results in reduced performance...it's also messy. The crankshaft and countershaft seals are of the wrong type, improperly installed, and usually of poor quality.
Neddle bearing vs. bushing on the con-rod small end:
There is nothing wrong with a needle bearing on the small end. This has been done in 2-cycle engines for as long as I can remember. The Suzuki trail 90 that I had as a kid had a needle bearing on the small end. The thoughts and theories that have been bandied about on the internet regarding this are wrong.
What is wrong is the fact that the piston was not fitted properly to use a needle bearing. There is a HUGE gap between the width of the con rod and the piston boss for the wrist pin...this allows the needle bearing to float out of the rod. 25-30% of the needle bearing leaves the rod and provides no support or bearing surface at all. This is an easy fix.
The idea is NOT to offer high performance engines in the traditional sense. High performance can also mean longevity through precision components...yes from the precision assembly there will be a horsepower increase...but it will not be such that it will overpower the mechanicals of a bicycle. 5 horsepower is reasonable, and plenty for an engine powered bicycle.
Jim
