How to Disable the Ignition Retard Mechanism on the SV

By Stephen George

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…
In certain 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
What follows is essentially a description of the work done on my bike by my dealer, at their suggestion.  I have simply taken some pictures and filled in a little background information.  My bike is a UK, 2001 model SVS.  I have purposely made this article quite noddy, for those who have never delved under the tank before, so I apologise if you’ve heard it all before

What’s the plan?

Simple.  If the ignition controller doesn’t know when the bike is in 2nd or 3rd gear, it will use the same ignition timing as for all the other gears, so no power loss. 

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 – have a look at the “Neutral Indicator Light Switch” in the Wiring Diagram picture.

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.  (As an aside, there is a mistake in the wiring diagram.  The red/yellow wire does not turn into a yellow/blue wire as shown, at least, not on my bike.)

What to do…

The wiring we need to disconnect is located under the tank.  In order to lift the tank and gain access, we must first remove the seat.  Begin by undoing the bolts that hold the black plastic side panels in place (there is one bolt per side) – see Picture 1.

It is not necessary to remove the plastic side panels, they can be swung outwards to reveal the seat mounting bolts (one per side) – see Picture 2.

Undo the seat mounting bolts and the seat can be lifted clear.  Next undo the two bolts on top of the tank at the very front – see Picture 3.

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 – see Picture 4.

The wiring we need to gain access to is located on the left side of the bike, near the airbox, where there is a rubber boot that covers a 4-pin connector – see Pictures 5 and 6.

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 – see Picture 7.
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.
That’s about it.  Now you’ll have enough power to wheelie on half throttle.  Ok, I lied!  Don’t expect miracles, I don’t think the increase is huge and remember it only affects 2nd and 3rd gears, but it must be a worthwhile modification or my dealer wouldn’t have suggested doing it, and it doesn’t cost you anything.

 
Oh, I nearly forgot… In the best Haynes tradition, re-fitting everything is simply the reverse of removal!