hi i have a gilera runner on a 07 plate new shape basicly its an sp 50 and i want a 70 kit i have 150 pounds ive got a short list but wich is best pm tuing 70 kit ?? 13 bhp aparently malossi non mhr rep 70 kit or the polini 70 kit possbly even the stage 6 one ???
Metrakit, its around 150/160 but its the best 70 ive seen on a scooter. mate had built one on his runner and it was belting out 14/15hp
What other mods does that bike have? I have heard that Polini sport kits gives better power and is more reliable, stage 6 has more power but can reduce engine life - as with most things, you can't get more power without loseing something else!
is that, you have £ 150 in total, because to set up the cylinder, you will need at least 2 jets for the carb, and several sets of rollers, better a box of jets and box of rollers. given that you haven't a race crank , probably the best kit you can afford is the stage six street race, owned one and great performance for the money. You don't mention a pipe, so take it you are running stock, because you don't want a revvy pipe on this kit, as that could well snap the crank, as it did it to me and another forum buddy within 6 weeks of fitting it. So either standard or a sport level exhaust is ideal. It is twin ringed and cast iron, as the Polini and Malossi sport kits, makes similar power, but where they start to drop off, this kit keeps going, giving a good few mph increase over them. if you can get some more cash together, the Malossi would be my first choice, second Polini. I must admit though, when I stripped the street race after 1200 miles, it was as new condition. forget about the PM tuning, that is a very revvy kit, not suitable on a stock crank.
What about the top performance trophy 70cc kit on scooter attack, they are pretty good it seems and quite cheap for what you get - 100 Euros for the 70cc sport, 6 port or what about the Motoforce 70cc midrace - 124 euros for 12 to 15bhp. https://www.scooter-attack.com/shop...MF2714041-Cylinder-Motoforce-Racing-70cc.html What power can an OEM crank take btw and what rpm? I guess that as the OEM crank isn't a full circle crank the case compression would be less so would be lower power than a full circle crank?
the con rods tend to snap at the piston end, obviously as it is the thinnest point. I couldn't quote a bhp threshold, as I don't know, but it seems anything around the mid-race capabilities sooner or later snaps them. One lad on a street race, got a few hundred miles over the course of a week, I got 1200 miles, and I ride 70s respecting the cc. Of course like anything, some get away with it, or don't confess their disasters. Maybe Gilera bought in a whole load of cranks which had a metal fatigue problem. the bottom line is that if the con rod goes, it is an expensive repair if you can't do it yourself. It normally damages the bore, and sometimes damages the cases. So new crank, bearings, seals, and a cylinder, rebore in a cast, if you are lucky, but then the cost of the rebore and over size piston, is the price of these budget kits, so might as well get a new one. The trophy is supposedly a good kit, tried and tested. Didn't mention the Parmakit either, some have had a result with it as a budget commuting kit.
What conrods would be best with the 70 kits then? I have heard that Hebe cranks and rods are used in the stronger race engines
I only really know the scene up to and including Stage 6 racing, that spare engine was going to be a R/T project, but decided I needed a more relaxed cruiser, so use the 172cc for distances and the 70 for blatting round town.
