Gear selection restriction
Bikes sold in Denmark are limited to an even dangerously slower 30.58 kph (19 mph), this is done by restricting owners shifting higher than 3rd gear by means of a different shift cam plate. The correct cam plate for reaching 4th 5th and 6th gear is part number: (Aprilia 847038) you'll also need to swap the 11T front sprocket for a 14T sprocket part number: JTF1128.14
Refill the transmission with 650cc JASO MA2 API SJ specification 10W/40 4 stroke motorcycle engine oil, fill coolant/antifreeze no higher than the overflow bottle maximum mark. If fitting brand new clutch plates.. don't forget to pre-soak them in fresh oil a few hrs before installation. Always use OEM Derbi clutch plates for the highest durability and service life.
Polini CP jetting and Premixing
Drain off all fuel from the tank.
Get a useful oil measuring bottle, part reference: Polini 121.500
Fill to 5 liter mark on the 3% scale with 2 stroke oil meeting API TC or JASO FB specifications, add this to 5 liters of fuel. Shake the Jerry can vigorously and then pour the premixed fuel into the tank. When filling up at fuel stations' always pour oil into the tank first and add fuel at the quickest rate the nozzle allows w/o creating a "fountain" effect, squeeze the front brake lever and pump the forks a good few times before re-starting the engine.
*Use the brass nut on the cable's angled piece.
*Take out the carb throttle slide needle and put the clip on 4th notch down.
*Remove the float bowl and swap the pilot jet for size (49)
*Swap the main jet for size (92)
*Turn the pilot circuit air screw clockwise until fully seated, then turn anticlockwise 1 full turn (from 12 o'clock to 6 o'clock = half a turn). DO NOT
search for the highest idle rpm or snappiest throttle response while adjusting the pilot circuit air screw, this will only result in a lean A/F mixture.
*Throttle stop screw (idle speed adjustment): engine should always stall after idling for a few seconds. Keep the throttle twisted slightly to prevent stalling when coasting to a stop or while stationary. If you wind the throttle stop screw in too much, rpm's will hang when closing the throttle. Resist the urge to screw it in every time the engine's fully warmed up.
rely on spark plug insulator color or piston wash deposits for providing safe air/fuel ratio indications, these old wive's tale methods are highly inaccurate.
Go for a ride' warm up the engine before completing a few high speed full throttle runs, during this you will notice the engine begin to sputter before reaching the exhaust's rpm limit. While this is happening the engine is firing on every 4th cycle "4 stroking". Reduce the main jet size by 2 numbers each time until this 4 stroking stops.
The bike may still lose forward momentum when rolling from half - full throttle, except the 4 stroking @full throttle has now disappeared. It may speed up when rolling back to half throttle. Reduce main jet size again by 2 numbers each time until the bike maintains forward momentum w/o slowing down @full throttle.
While cruising steadily in 6th gear, pull the clutch lever in and hold WOT (wide open throttle) for 1 or 2 seconds. With the engine under no load it should 4 stroke.. preventing the engine from reaching the exhaust's rpm limit. 4 stroking should also appear @1/4 throttle under normal load conditions in all gears. If it 4 strokes massively like a builder's concrete breaker tool, lift the needle clip one notch higher to reduce the severity.
If you live in high altitudes or hot average temperature areas where air is naturally less dense, you might find an 80 main jet overly rich for the Yasuni ML pipe. If so' try the 60 - 78 pack: Polini 370.0001
2 strokes are designed to burn dirty, emit blue clouds of smoke and sputter through 1st / 2nd gear after idling for more than 5 seconds - especially while running healthy premix ratios. The main reason mx and road racing involves whacking open the throttle many times on starting grids before the gate drops or amber light turns green.
Replace the OEM ignition
CDI module on bikes sold in Denmark is restricted to 30 KM/H.
The Ducati ignition stator only lasts a little while before giving up it's ghost, cheap China and Tiwan stators are even worse. When the stator fails.. don't go replacing the CDI module, as this never really fails. Replace the whole ignition with the french made MVT Millenium EXT 111 kit.
..but don't ground the Blue
45 km/h restriction wire..