Any pictures of inside the 5G?
Even the entire kit pictures of everything don't show it let alone what kind it is or any ratios!
The closest thing I could find with even a hint as to what is inside the 5G was from the link to buy a replacement on BikeBerry
http://www.bikeberry.com/engine-kit-parts/4-stroke-parts/4-stroke-transmission.html
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(edited Q&A text from above link)
Q: Does this fit the Hunsang 49cc?
A: The 4-stroke transmissions that we carry will work with our most current models of the 4-stroke motor.
However older models of the Hua Sheng motors are not always compatible with the current model transmission.
Currently our transmission are coming with a:
10 tooth drive sprocket, with a dual chain in the transmission.
Q: can you adjust the tension of the inside chain?
A:
Unfortunately, you are not able to adjust the chain tension on the inside. .
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I think I seen one of these a few years back when I was first starting, a repair for an even older bike.
Dual sprockets at each end and 2 thin chains with an oil bath and no way to adjust them.
That design even made the Stage III three gear oil bath transfer case look like an improvement because real gears don't stretch.
Anyway...
From what I can glean from the sparse info anywhere steer clear of the 5G.
For bolt-on's stick with an adjustable T-belt (Toothed belt) transfer case, they vary in quality at the clutch and freewheel, but an adjustable, clean and quite transfer case does make a difference in riding comfort and ease of service.
In short I'd rather dick with the 7G's clutch than trying to tension or replace 2 chains with no adjustment ability....
But then again the 5G clutch bell would need to be in a bearing system to support the sprockets so better than the 7G there...
Don't ya hate those trade-offs?