The real Zongshen motors that hit the market maybe five years ago were decent, depending upon the exact model. Some models had their problems, mostly electrical and shifting issues and these could be corrected, for the most part. Some models actually came with Japanese bearings in them. These also cost more than the ultra-cheap stuff currently on ebay. The Z108 is the only unit that's been around long enough to have a record of field service. The Achilles heel of these engines is the gearbox. They're known for wearing out the third gear cluster and for having soft shift forks (virtually all PRC motors have these issues, particularly the soft shift forks). Unlike nearly every other PRC motor, parts can actually be had for these. For non-race use, it is possible to get decent service life out of one. That's where the good news ends.
Trying to find a genuine, high-spec, Z108, preferably the secondary clutch model, has gotten very difficult. PRC bike parts are built to different cost/quality specs, levels 1-5. Quality costs more to produce. With the Waldomart marketing mentality that's taken over, there's mostly engineered-to-sell lookalike product available lately. Even dratv gave up trying to sell the Z108. At $700, a proven motor sold on quality doesn't look as good as a prettied-up $265 125cc motor sold on price. Pick your brand, it can say anything on the cases. Copyright enforcement doesn't exist in PRC. Three guesses which wins in mass merchandizing, quality or price? And that's the issue, you have no idea what's being offered for less than $300. There are so many variations, cobbled together from odd-lot parts, many of which failed Q/C, that it's a total crapshoot. Setting aside consideration of quality issues, finding parts is a nightmare. Even the hardcore devotees who want to fit aftermarket cams, heads, bore-up kits run into major headaches trying to figure out what parts to buy. The aftermarket vendors don't have it any better trying to navigate through an ever expanding blind maze of motors.
If you want something beyond a dixie-cup, use-it-and-toss-it engine, ask the seller for a parts list and try to order some small replacement pieces before you buy that engine. A solid dealer, selling a legit zonger will be able to provide product support (setup, wiring & repair information) and supply you with replacement parts. The market has undergone a rapid and dramatic shift over the last year. The one constant is that if it seems too good to be true, it probably is. It's not that acceptable product doesn't exist. At issue is how, exactly, one goes about finding it.
