Truth about gy6 150cc scooters

[qwertydude]

Yes except I'm also one in real life. This is why us engineers hold such disdain for designers. You make assumptions, don't care about science, and don't believe facts when presented clear as day in front of you. I've met enough designers whose principal talent is BS. I'll tell you one thing, you don't have an open mind, None of us here claim our stuff is as good as the name brand stuff because we know it's not but we love our Chinese bikes still for their value, but we understand the limits of their quality.

Where I work we're not even allowed to buy Chinese steel for a good reason. We make critical helicopter and turbine engine components and because of rampant certification falsification in China, Chinese steel mills can give us contaminated steel which when hardened beyond Rockwell HRC 40 will catastrophically fail without warning. We buy metal from India, Europe, Japan no problem the certifications can be traced, verified and the steel tested. We sent Chinese steel to an independent certification lab and came back half of the samples were contaminated even though they were "certified" by the Chinese company as pure. All it takes to buy a certification in China is a few bucks.

And the difference is you've posted claims and opinions with no proof. Everyone's might be an engineer on the interwebs but at least those people try to back their claims up with something resembling proof. You're basically saying a Ford Model T can be made to the same quality a modern Honda Civic with just some minor upgrades. It simply can't. And the GY6 is a nearly 50 year old design so most definitely technology has progressed way passed this nearly half century old design.

When I say the metallurgy is different even between different GY6 engine manufacturers it's no joke. For example in our cheap Chinese scooters how often do we stress adjusting the valves? It's usually the first thing we suggest when engines have running or starting problems. I had a Honda Metropolitan it's 50cc. I sold it at 15,000 miles and the valves were still in spec and didn't need adjustment. Try going that far on a GY6 without adjusting the valves. You won't. Valve recession is one glaring hole in your Chinese is just as good as European and Japanese brands. You can replace all the hoses you want. Unless you can pop those cheap stainless valve seats and replace them with real Stellite valve seats you're not gonna have the same valve durability period.

Do you even know what the ceramic coated cylinders in SYM's engines is? It's Nikasil. If you've never seen it before this stuff is so durable when your engine finally loses compression at 75,000 miles all you have to do is put new rings in and you'll be good to go. It literally does not wear out and won't need reboring or rehoning. But in order to make an engine that durable you need a more solid lower end, better cranks and connecting rod bearings and crankshaft bearings. Something the Chinese GY6's lack because of the need to keep tighter manufacturing tolerances and strict quality control all of which costs money which is why the Taiwanese scooters cost nearly as much as the Japanese ones.

I've posted specific models and makes you can look up. Even in the best possible OEM manufactured condition the GY6 engine design is limited in its possible specific output, ie hp to displacement. I could go further but it would take a lot longer posts. But if you can refute any of my claims with facts and not opinion. Please feel free. As an engineer I actually welcome it, as taking constructive criticism is part of the job, you need to be able to take it and use it to design and produce better products, improve quality and reduce costs.

But right now you're the one whose quite short on facts and way too long on opinion. Back it up and make me eat my words. Again I welcome it.

[kz1000st]

OK, here's my two cents on this topic. Will a Chinese GY6 last as long under the same conditions as a Chinese SYM GY6 or Honda PCX. No. That's why you have to observe the limits. Cruise all day at 45 mph and 3/4 throttle on a Chinese GY6 150, it will last a good long time. Someone mentioned Acworthpatricks Automoto, he just passed 40,000 miles. What he didn't mention is his Baccio GY6 scooter. he's well above 45,000 miles on that and, yes, he just replaced the rear gears but not the engine bits.
What I find interesting is this "My expensive 50cc scooter will outlast a cheap GY6". I would think so. At $2000 for a 50cc Piaggio Typhoon or Aprilia, I would hope so.
Here's my point. Plenty of people out there are nailing down incredible miles on cheap GY6s by riding with their heads. Truth be told Chinese GY6s are like Harleys. Mod and ride them hard-they blow up. Leave them stock, do the maintenance and ride sensibly and they get high mileage.

It's a Universal Formula.