This is just my opinion on the cylinder kits. Polini Sport I believe this to be one of the best low end sports 70cc kits you can buy, I've personally owned two. Took 2 years of abuse. You know how much I ragged my moped. still took the abuse. will work perfectly fine on a standard crank as long as It's low Millage. You can run a Leo-vince TT and make around 8.9bhp or with a little bit of modification you can run a Yasuni R and put out around 10bhp. Malossi sport Don't know much about this kit, But it is a high rival to the polini sport. It is known to have slightly better low end acceleration than the Polini sport but not as much top end speed. Still would be a very good beginners kit. I'd personally run a yasuni r or a Stage 6 Sport Pro. Stage 6 street race This is the cheapest best quality kit you can find on the market, It will suit your every day needs and be very wheelie happy. this is also a very good kit if you don't intend to inform your insurance company due to it having 49cc stamped onto the cylinder kit, so the police wont know unelss they rip your engine apart. Most police are too thick to do this and can't be assed. This cylinder would work good with the sport pro rep due to it being designed to run on that Polini corsa This is a very good kit but should not be ran on a standard crank due to 30% more power than the polini sport this is still a iron kit so will still be reliable for air cooled engines this will need a better variator etc and would bennifit from a bigger carb, You could run a yasuni r/polini team 2 or a stage 6 pro pipe and would quite a nice engine Mhr rep This is about as good as a two ring cylinder can get, Made from ali so has better heat propertys than Iron kits and will give the most power. Only downside is due to it being a Ali kit the piston rings will wear out quicker so you will be replacing them every 1500-2000 miles. You will need to run a good quality oil too. This kit would work best with a Yasuni r or a c16 if you want to mod it a little bit. This will need a upgraded crank also due to putting out around 13bhp I personally would go for the Mhr rep due to always having my engine apart. But it's your personal preference if you want something you can ride every day go for the polini sport as that will last 10,000 miles before it needs replace the Mhr rep more 6000.