Stock oil pump with Stage6 Sport Pro mk2?

Ben Dover Swe

New Member
Bought this setup and hate pre-mix. What to do?
Is it possible/advisable to run stock oil pump on an Yamaha Aerox (Minarelli lc) with a Stage6 Sport Pro mk2 cylinder kit? Other parts is (same as in the previous thread):

  • Cylinder Kit: Stage6 Sport Pro Mk2
  • Exhaust: Stage6 Replica
  • Carb: Geniunie dellorto 17.5mm with 85 main jet
  • Crankshaft: Stage6 HPCs (came with the engine, its 10mm pin AND according to its S6-part number its apparently for minarelli vertical ac, while I have horizontal lc - hope this will not mean trouble! Please either alert me or calm me.)
  • Bearings: NTN or SKF or similar (was installed already)
  • Intake manifold: Stage6 intake and reed package. (glass fiber petals i think)
  • Airbox: Stock airbox, not modified
  • Reed Valve: package with intake
  • Variator: Stock with 4,6g weights (3x 4.7 and 3x 4.5)
The instruction booklet say to run with 33:1. But people say that S6 have to give high margin as some riders use this cylinder kit for mid race.
Guides say 50-40:1 would be enough for 70cc sport.
I am not sure but I think the minarelli/aerox stock oil pump delivers 50:1 (2%) - would it therefore be OK to run stock oil pump on this setup without premixing?

Word of warning to the public regarding TNT:
I bought an "adjustable oil pump" from pedparts, it leaked a lot of oil which is catastrophic. We had to disassemble a lot to access it (exhaust, cylinder kit, water pump, flywheel, magneto, oil pump), and tried seal it and re-assembled. Still leaked some, noticed after standing still for a couple of days. So even if we got a malfunctional specimen, the quality is very bad and to be considered unreliable - if the oil pump fails the engine go bye bye. TNT brand apparantly, which is not stated in the shop - then I would evade it like the plague from beginning. TNT is famous for making stuff that breaks by looking at it. During this build we also tried a brand new TNT carb that the port was stuck straight out of the box - we had to remove it by force and sand it down, so it would slide up and down. Then when assembling, the oil hose nozzle (thin plastic) cracked by the gentle force of putting on an oil hose.
Advertisement - register to remove this

Stock oil pump shouldn't be much of a problem. I doubt that the stock oil pump is around 1:50. Usually they are controlled by the throttle and the more you open it, the more oil will flow. This doesn't really correlate to the amount of gas, so you can say it's 1:50 all the time. Lot's of people use the stock oil pump with racing cylinders and never see issues. The correct main jet is much more important!

Advertisement - register to remove this