Any of the new Lifan 140cc are all 4UP now....as said the older versions 1DN-3UP were not as robust.
I bought one from Hoopers last year,a 1DN-3UP,not as educated as I am now :35: and the date code on it was 2008 :13:
But...I have over 1700 miles on it now,probably more with all my inaccurate mileage readings from numerous wheel changes, and the thing still runs perfect.Not easy miles either with full throttle off road shifting just about every time I ride my White Bike.I am wanting to see how much it can take so I can upgrade
I'm sure the new 4Up versions are every bit as good as the 125cc 4UP engines,I have 2 of those,they shift butter smooth and run vibration free at all rpm's.
If I ever kill my older 140cc I will not hesitate getting the new and improved version.Just too much easy cheap and fun power to play with.Like everything else improvements are on going and quality improves with time.
I do have 2 genuine Honda engines in the garage and will rebuild some day for a purest built bike,but to get the same power at this low cost would be difficult.In the meantime these little "disposable" engines are hard to beat
This vendor has been good,but you have to sign for the package upon delivery,so keep that in mind.
He seems to be out of stock but there is another one also
Lifan 140cc Oil Cooled Engine Motor Set CRF50 XR50 XR SDG SSR 110 125 V | eBay
I haven't bought from this guy,but there all coming off the container ship in Long Beach...
New Lifan Manual 140cc Oil Cooled Engine Kit for Honda CRF50 CRF70 XR50 | eBay