to Disable the Ignition Retard Mechanism on the SV
What’s it all about?
As you probably know, the SV has a “mapped” ignition system, which by modern car standards is fairly simple. A small box of electronics (I shall call it the “ignition controller”) measures things like engine revs and how far open the throttle is, then decides the correct time to fire the spark plugs as each piston approaches the top of its compression stroke. If the spark occurs too soon (i.e. the timing is advanced), pinking will occur with the possibility of engine damage; if the spark occurs too late (i.e. the ignition timing is retarded), then the power output from the engine will decrease. As the bike does not have ram-air induction and a pressurised airbox, you would expect the ignition controller to use the same “map” (or set of ignition timings), regardless of which gear the bike is in. This is the case, but with a subtle exception…
territories, the bike has to pass a drive-by noise test, which apparently
involves accelerating hard past a microphone in 2nd and 3rd gears.
In order to get through this test, it seems Suzuki decided to cheat!
They designed the ignition controller to retard the ignition timing when
the bike is in 2nd and 3rd gears. This must reduce the noise enough
to pass the test, but it also knocks the power back a little bit too.
This is obviously a Very Bad Thing! For all the other gears, the
standard ignition timing is used
The ignition controller detects when the bike is in 2nd or 3rd gear by a switch in the gearbox. This switch has four contacts, as it also indicates when the bike is in neutral
One wire is a common earth (black with a white stripe in the diagram); one detects neutral (blue); and the remaining two wires (red with a yellow stripe and green with a blue stripe) detect 2nd and 3rd and go to the ignition controller. It is these two wires that we have to cut or disconnect.
It is not
necessary to remove the plastic side panels, they can be swung outwards
to reveal the seat mounting bolts (one per side).
As the tank
is hinged at its rear, the front can now be lifted to gain access to the
wiring. There should be a metal rod under the rear seat to prop
the tank up.
Slide the rubber boot forwards to gain access to the connector. The 4 wires entering the connector from the rear are from the gearbox. The red wire with a yellow stripe and the green wire with a blue stripe are the two wires we need to disconnect.
In this case, the 4-pin connector has been dismantled and the relevant contacts removed from one half, rather than just cutting the wires. Either way, it is important to insulate the bare ends. Heat shrink sleeving is preferable, or some self-amalgamating tape that most DIY shops sell. Electrical insulation tape is pretty useless as it tends to fall off when it gets hot.
Willem Peters Writes:
Jody Lovejoy Writes: