Well the 180kmh restriction uses a hall-effect sensor in the speedo, but that is based on speed not rpm. My rev counter seems to working fine but does anyone know if there is some sort of gear indicator fed through the rev counter/speedo since the issue seems to isolated to 5th and 6th.

I'm having the same issue hereom my 93 nc31, would love to know a solution

what size sprockets are you using.

my nc31 maxed out at 160km I'm running stock size front sprocket and a 40 rear. Didn't matter what gear I put it in either would not go any faster, got upto that speed really quick though.

Any chance there are 33hp restrictor washers in there?

Hi Guys,

I have a very similar issue, 1st thru till 4th the bike will happily rev upto 12k rpm, and the speed will climb quickly, but once i hit 120km/h acceleration slows down and I get max 140km/h from 5th and 6th. Also, I can only use half throttle because if I open the accelerator more the bike sort of surges as if it isn't getting enough air or fuel or both.

Any help guys?
TIA