Reaching 50mph on 66/80cc

Next mods to push over 45mph

  • Stuff crank case

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  • Advance timing

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New Member
Mar 23, 2020
Hello family and friends! I have been trying to obtain 50mph on my pk80 and am getting closer with every mod. Right now I'm hitting 41mph(gps) and know it will go faster.
  • Pk80
  • High compression head
  • Copper head gasket
  • Ported/matched intake/exhaust
  • Ported/matched knifed transfers
  • SKS bearings crank/clutch
  • G2 Reed w/19mm intake
  • Dellorto SHA/HP 15.15 with .68 jet
  • Windowed/ramped piston
  • Fatbelly expansion chamber (cheesy but cheap, temporary till mz Miami restocks the mz65 pipes)
  • 36 Tooth Sprocket
  • NGK B6HS Plug
  • Stock CDI
  • Stock timing
  • Stock magneto
  • .6 gallon tank
  • 20:1 fuel
  • Spring chain tensioner with sprocket roller
  • Custom tank mounts
Right now I have a wicked power band that takes me up some pretty good hills. 20-30mph is super quick. 30-40mph pretty quick too. At 40mph it totally feels like it wants to go faster, but runs out of fuel. I might try upjetting a little more to .70-.72 and see if I get more mph. I have not stuffed the crank case. Or advanced the timing.
I have also read that the dellorto clones you can drill out the top hole of the jet tube to allow more high rpm fuel delivery. And also modify the slide. I am reluctant to get a mikuni carb or anything else as I've read the dellorto should be able to get to 50mph. Maybe......

Does anyone have advice or has anyone reached 50mph on similar setups? What did you do to get to 50mph? View attachment 104024 View attachment 104025 View attachment 104026 View attachment 104027


New Member
Jul 8, 2020
Personally I'd start by changing your fuel:0il mix ratio as that can make a lot of difference and now the negine has been more than broken in there isn't much harm, I would try go down to 40:1,
Also Rejetting to a larger jet could help if its possibly 4 stroking (whats it sound like ?)