Third step: fairing or, better, updating its early 2000s style and lowering the seat to facilitate hard area riding. The evolution on which I worked all these years led to the current look, i.e. tail unit and filter box replaced with the 2016 model, creation of a handmade aluminum tank with a carbon cover which can carry the more modern conveyors of the 2010-12 4-stroke Yamaha.
This tank, besides giving it a newer look, has the advantage of lowering the front of the seat, since the tank cap area is much lower, as the post 2010 bike trend requires, to facilitate the forward movement on the seat when curving. Another advantage is that it lowers the center of gravity since the liters of fuel lay lower. Total capacity: 8.1 liters, enough to cover the same mileage of other 2-stroke bikes that carry 9.5 l, thanks to the efficiency obtained by modifying the engine (that I will illustrated later).
Fourth step: installation of the PowerCDI control unit. A vigorously pursued installation, since the YZ was not included in the manufacturer’s list of supported bikes. To do it I had to modify the bike wiring and ask the manufacturer to carry out a specific study on the electric parameters of the Yamaha stator, that in theory shouldn’t have been able to work on the PowerCDI electronics, but with the right settings/parameters (this engine control unit is completely reprogrammable/reconfigurable) it turned out to be perfectly compatible. Later, the manufacturer has also created a simple adapter that allows the use of the original wiring of the bike.
This electronic upgrade allowed the mechanical setting of the engine to be configured (squish, carburation, valve adjustment, ignition timing) for maximum efficiency and performance. A carburation so clean would be useless on an engine without electronic dynamic controls, as would a greater squish (which lends combustion efficiency).
It also grants low consumption and high performance, this obviously compared to similar motorcycles.
The YZ engine is already designed to house the gearbox sensor, which however is only used to signal the neutral to the control unit, but if you install the sensor of the 4-stroke models (identical and compatible) you can make the most of the considerable advantage given by the PowerCDI of having ignition and Dynamic Power Control mappings customized for each gear. Specifically, I preferred, for example, a control on rpm increase tightly connected to the gas control in first gear. Practically, in this way, there is no need to use the second gear together with the clutch on slow and slippery ground, since the first gear (that I could never use before electronics came into the picture) is already soft and not nervous.
Fifth step: installation of the 300 Athena kit. I personally love torque and easiness of use, and the increase in displacement helps these two aspects. Once again, thanks to the PowerCDI, I was able to set this 300 in an otherwise unimaginable way: squish at 1.1 mm.
Therefore, promptness (when you hit the gas), combustion cleanliness and reasonably low consumption. However, this rather compressed setting amplified a problem I already had: no electric starter which is indispensable on any high-powered 2-stroke enduro.
I’m short and the force needed to kick-start the bike was too much to be able to start it in precarious situations.
Sixth step: electric start installation. The idea originated from the electric start of the GasGas, A rough measuring of its dimensions indicated that it could probably be housed even near the crankcase of the Yamaha without requiring considerable modifications.
And that is how it was added. I cut the GasGas crankcase, welded a dedicated adapter-flange shaped for the crankcase of the Yamaha, added a weight I created with a lathe above the flywheel of the Yamaha to which I could fix the sprocket.
The start is powerful and never fails. To prevent wear (suffered by this type of start), the two main axes, that originally move on the aluminum crankcase, have been equipped with self-lubricating sintered brass bushes embedded in the crankcase using a CNC milling machine.