I spent about 4-5 hrs today assembling the Livefastmotors chain drive 40cc 2-stroke rack mounted kit. It would probably be a 2 hr job if I had the proper instructions or were to do another. I basically ended doing a lot of things twice to get it right. The kit comes with a toolkit which is nice and all the parts (and some that you don't need).
I think the kit looks good and is not as complex as the Chinese frame mount, ie no muffler, carb, clutch, twist throttle, gas tank, wiring or air filter to assemble. It does have a gear box which isn't bad....especially if you had instructions. I used loctite or nylock nuts on all bolts.
Performance: with the centrifugal clutch and only 40cc does not produce the get-up-and-go as the 70cc Chinese engine. It helps to peddle to start and the acceleration is not as quick. I don't know how it would compare to the 50cc Chinese engine. I haven't clocked the top-end speed but I would guess it is slightly slower compared to the Chinese 70cc. I'm running at 5000 feet in Utah which is quite higher than my 3000 feet at home in Alberta. The elevation difference would also have a significant impact on performance. I haven't tried it on any hills...I hope to tomorrow. It sounds about as loud as the Chinese 70cc.
Summary:
weakness:
1) No instructions. The instructions on the internet are for a different motor and the mounting is significantly different due to the placement of the gas tank.
2) The pictures on Ebay are not the same engine. It does say this in the description but it would be nice to have the correct pictures of the engine kit you are actually buying.
3) $95 for shipping and handling is a questionable practice. Obviously the vendor is building in a fixed profit margin through the shipping. It makes the total price to be $185 to $250 depending on what you bid....comparable to the Chinese 70cc total price.
4) Shipping was quick but kill switch was smashed because the engine was laying on top of it.
5) It has a very small gas tank
strengths:
1) The kit would be simple to put together if one has instructions.
2) The kit is less complicated than much of the competition
3) The vendor shipped a new kill switch the same day he was notified...not questions or hassles.
4) Performance is not bad for a 40cc centrifugal clutch unit.
5) I think it looks good.
6) Comes with a tool kit
I built this unit for my college age son for transportation from home to university. He is not mechanically inclined and doesn't have the time to tinker. I think it will suit his needs. I would also recommend it for ladies who don't like working a clutch.
It will be interesting to see how it handles hills.
See
YouTube - motorized bike rack mount for video
Review of Livefastmotors chain drive rack mount 
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