Yes you need race springs for 7mm lift. There is a lot to cams. Lift is nothing. There are a ton of cams out there with 6.9-7mm lift, but they all perform completely differently depending on the lobe profile and centres. Also the durations and retard/advance of the cam in the engine.
Little real development has gone into cams for these engines IMO. It has been a case of adapting already existing profiles from other engines.The best performers so far are aftermarket Honda cams which have been adapted to suit. You'll find most of these other sellers have had China copy these Honda cams and had cheaper quality ones made. Another thing which has been done is to grind the base circle off a stock cam which increases the lift and duration to a small degree, but is a very unsatisfactory way of altering a cam. The thing about using cams well designed for Honda's, is that the 50 Honda head and engine is really a completely different machine than something like the Lifan with a BVH. The bore/stroke/rod ratio is completely different and changes the cam requirements completely. Why do you think a built 124 Honda makes so much power compared to a built 125 China? Its simple, the Honda has been developed properly. A 125 Lifan can be developed to the same level, but it won't be done using a Honda cam.
Cams sold to the general public are made also so that anyone can drop one in without degreeing the cam properly and get away with the cam being out by a fair amount without risk of things colliding.
Having taken note of all that, you will still see a good improvement in your power output by carefully picking out available cams you have heard are good for the type of output you want. If you know what your on about, and have a specific cam requirement, PM me.
BTW- that guy has 2 neutral's and 2 negative feedbacks out of only a small amount of sales. That is always a warning sign for me.
