Crankshafts and bottom ends
- Thread starter biknut
- Start date
Hey this is a wholesome family oriented forum where discussing your crank and bottom end may be too sexually explicit and inappropriate.
TiM
TiM
IMHO, a forum section for that would be overkill. All that's needed is a few engine disassembly threads 
Oh wait: there's already a bunch of those!
Oh wait: there's already a bunch of those!
Do say. How about you elabrate a little bit about how you replace your rod. Then if it's not too much trouble, please explain what method you used to true the crank afterwards.IMHO, a forum section for that would be overkill. All that's needed is a few engine disassembly threads
Oh wait: there's already a bunch of those!
Really? When I think hub, I'm usually thinking wheels. Gearboxes, and sprockets don't really suggest crankshaft to me either.
How about,
Bottom end, Crankshafts, and Rods
Lets face it, this is one of the weakest areas in a china girl motor, and we don't have much information about them.
Use a big hammer that's how they slapped them together in the factory in the China shop making fine china that is. Hammer press!
Or you can get super elaborate with a press of sorts and some all thread rod. You will have to construct one with steel plates. Thick ones. Also so ya don't warp it going back together a custom thickness plate or shim of sorts to set between the fly wheels when assembling or pressing apart. Could keep it straight if approached right? Think MC Hammer it's Hamma Time! The hammer is likely to get attractive at some point lol.
Still in a lot of press fit bearings and races in the like of wrenching when approached correctly is acceptable and common practice.
Or you can get super elaborate with a press of sorts and some all thread rod. You will have to construct one with steel plates. Thick ones. Also so ya don't warp it going back together a custom thickness plate or shim of sorts to set between the fly wheels when assembling or pressing apart. Could keep it straight if approached right? Think MC Hammer it's Hamma Time! The hammer is likely to get attractive at some point lol.
Still in a lot of press fit bearings and races in the like of wrenching when approached correctly is acceptable and common practice.
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Certainly. If I'm going to bother, I'll unbolt the old one and bolt in a new one. Fiddle with it til it works. If it doesn't, replace it.
Of course. If I'm going to bother, I hammer til it works. If it doesn't, see above.
Therein lies the issue: many people consider the chinagirl to be a disposable toy engine. The Chinese seem to build em like so.
In this instance gearbox vs "bottom end" may be a minor matter of semantics as with most motorcycles, mopeds etc the gearbox is the bottom or lower end... granted the "china girl motor" doesn't have a transmission per say, but it does have reduction gearing, as does most of the small engines we use - thus "gearbox" is a general, all-inclusive term in common usage and covers many variants and components. While we could alter the title instead of a whole new subforum... it could make for a looooong title lol as "Hubs Gearboxes and Sprockets" is meant to be general, covering all aspects of power transmission, internal or external gears, multiple gears and/or just reduction, cranks, shafts, sprockets, etc.
The term "bottom (or lower) end" is also ofc in common usage, but it's usually very specific & excluding other topics which insofar as subforums are concerned, starts to lead down the path of having a separate subforum for each and every individual component, which needless to say gets to be problematic.
As not everyone has or is interested in one engine type alone, we try to strike a balance between such generalities and specific areas of interest, in fact every time a new subforum is discussed we find our memberbase is split between those that say we've too many as it is and those that say we've not enough - so in that we try to strike a compromise as well.
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Alright I dig what you're saying. It's only a suggestion anyway, no big deal.
What about this idea, and then I'll shut up about it? Instead of starting a new forum, change the name of to
Crankcase, Gearboxes, and Shafts
Move the hubs to the wheels forum, since a hub is part of a wheel.
I agree most of the china girl motors are not much better than toys out of the box. I see new people lamenting that fact everyday. It doesn't have to be that way though. This forum is partly about lifting people up, so they can do what they need to do to make their bikes dependable.
I don't consider my bike a toy, even though I use it for fun.
No worries man, feedback & suggestions are always appreciated! Hubs are tricky tho, yes they're part of the wheel... but they can also be part of the drivetrain, jackshafted gearing is quite common and is why hubs were included - to encourage discussion of the various hubs used for such with the thought that any hub discussion not related to the drivetrain would be in the 'Wheels, Brakes and Suspension' section...
Amen to that
I think the only real issues regarding these kits are twofold, the first being how they're promoted as motorized bicycle "kits" when a more honest approach would be that they're motorized bicycle engine kits - as in, the engine itself is also a kit, only loosely assembled as to keep all the parts together. The second would be the expectations stemming from that somewhat misleading presentation as well as what you can reasonably expect from such a low cost investment - it really is somewhat unrealistic to think you'll get any sort of a quality, "finished" motor for that kind of money, let alone an entire kit for converting a bicycle.
While there will always be an element of randomness with such a low-cost engine, their absolute simplicity and near ideal bicycle conversion capability make for an excellent introduction to both basic engine design and motorized bicycling. Without such an inexpensive "toy" to experiment and learn with, far fewer people would discover the potential these bikes have - or the capabilities within themselves for that matter.
Some may resent the experience they've had with them, yet without that experience would they have discovered the alternatives? Would they, without ever having had an opportunity to so easily & cheaply experiment - invested the time and money it takes to build something so much more involved? Some would without a doubt, but I suspect the vast majority of our best fabricators cut their teeth on the much maligned "China Girl" kits lol
