Hi there. I have just successfully got my Stage 6 70cc kit going. Unfortunately they don't sell them anymore but Athena of Italy sell the same kit. They manufactured it for Stage 6 anyway. The Race version is what Stage 6 used to sell as the "Sport Pro". They sell the piston kits and gaskets etc as well.
Anyway I used a 17.5mm Oko carb as it has an electric choke. The standard choke fit right on. The 17.5mm Dellorto looks virtually the same and is probably better and Scootling in Wellington sell it. I could not find any pilot jets but for the Dellorto they will be available. I drilled mine to .45mm (i.e #45) and it is borderline rich (i.e.need 3 turns out on the air screw, the maximum allowed or it vibrates out!) I would say a size 40 would be best. Main is currently at 92 with the standard air box adapted via a custom made adaptor.(I will go down to about 90 or 87 once run in properly. See explanation below) I also installed 2 Motoforce airbox buttons to supplement the standard intake. I removed the long rubber snorkel. I wanted to retain the air box as it improves low speed power and looks stock. I don't want it attracting too much attention!The needle is on the second to leanest setting and it carburets perfectly. I have a Polini 17.5mm carb coming as it looks like it flows better for the same size and looks a beautifully made performance item at a very reasonable price.
I spent a lot of time with a Dremel enlarging the manifold to match the carb as best I could. It is quite small and unique to the scooter so couldn't get an aftermarket one to fit. I also think a 19mm carb is a bit wasted as there is no way it will enlarge to 19mm. I would have to custom make a manifold for a bigger carb than 17.5mm.
I am using a Stage 6 Sport Pro pipe and spent hours and hours jetting it wondering why it was slower than the standard scooter only to find it has a restriction in the header pipe so watch out for that! It is just spot welded in place so easy to remove. The Technigas never had that in there!
I have to admit after I discovered the restriction I removed it and stupidly thought I would give it a quick blast up the road knowing it was lean. Well it was flying and I couldn't stop myself riding it and it seized mildly. Got to 95km/hour though quite easily (with Polini gearing kit installed) that was with an 82 main so 82 is too small!!! Have since rebuilt with new piston and removed aluminium from Nikasil bore with Muriatic Acid. Came out perfect! I am also running 100:1 pre mix as well as the pump to be sure!
Use the thick base gasket under the barrel and rubber O-ring in the head. That will give the 0.7mm squish Stage 6 recommend (I luckily have a friend who reads German as there are no English instructions!) Make sure the head is turned the right way with the fins horizontal and the "overhang" facing away from the air flow otherwise the ducting doesn't fit well. I also removed the tin shield in the ducting for the same reason.
Lastly the transmission. I installed the Polini gear kit. It requires one of the standard gears be pressed off it's shaft and be pressed onto the Polini one. The other gear just swaps straight out. I got a bike shop to do that, or an engineer might be better. This guy was both so I trusted him!
I used 7.5gm 16x13 weights and the stock spring. I have a Stage 6 variator kit coming and this is the weight they use with a soft torque spring. I compared the stock spring to a soft Motoforce spring and they are so similar as not to worry. I used stock clutch springs as I value road manners but the stiffer clutch springs would no doubt give a fierce take off!
Bike cruises happily at 83km/hr at 9000rpm. Once run in and rejetted I am sure it will do 100 km/hr. I have fitted a derestricted CDI obviously!
Hope this helps some. I have spent quite some time working through this so if it saves you a few hours I will be pleased!
