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North UK


The “main jets” activate once you are beyond 10mph , otherwise it is the “pilot jets” aka “slow jets” that usually are responsible for:

  • Idling
  • Gear change transition  (revs change)
  • Starting   (part 2

There is also a “tube” that is narrow and very tall, beside each pilot jet, we can’t remove it as its permanent. That is responsible for starting & cranking the bike.


So I would advise:

  • Clean the carb thoroughly (it has many holes everywhere inside the skeleton body) and pilots + starter jets clog very very easily.
  • Float height must be 7mm  (even a touch can bend them)  , if in doubt about the, replace the floats for new ones , even the old ones look aged up, bits of it can crumble in to the fuel stream and clog the jets and rest of the carb body

Can’t find someone to Ultrasonic clean the carb ? (best)  , use multiple nozzles and a compressed air machine.    “Rattle Can” carb cleaners work but they can’t beat ultrasonic cleans or compressed air


Air System = The airbox was removed to get to the carbs, so cheak for air leaks here:

  • Under the inlet manifolds (sometimes old  O-RINGS will be the 100% reason bike has power losses as its usually ignored by most people)
    You will find the orings on the shop.
  • Inlet manifold for cracks , incase the stress of fitting parts back on might have cracked something
  • Airbox isn’t swallowing the carb mouths fully , especially the front.  Usually we fix the carbs to the airbox first and tighten nicely , then drop the whole thing nicely down to the fragile inlets.
  • Air loss / vacuum loss is one way to make the “taps, pump , carb ” parts not run or even crank the bike properly.
  • Check both plugs spark bright blue AFTER you fully charge the battery


try these and report back , and be sure to tell us what the issue was so it helps someone else in similar situation or come back with any pictures of where you get stuck at.

Hope this helps!

// Meditation doesn't mean you have to sit still....