Poor @ low revs? = Starter Valves...a guide

[Skids]

What the Starter Valves (SVs) Do

The starter valves have a few functions:

1. They allow sufficient air past the throttle butterflies to allow the engine to idle because the throttle butterflies are a pretty good seal on the throttle bodies when closed.
2. They also allow the engine idle speed to increase when cold. The fuel injected engine in the VFR doesn't have a choke in the traditional sense of having an extra butterfly to act as a restriction in the inlet tract, fuel enrichment is taken care of by the FI ECM and the fast idle by the starter valves moving to allow more air past the throttle butterflies. In the FiW and FiX models the starter valves are moved when you move the "choke" lever, on the FiY and Fi1 models the starter valves are moved automatically by the Fast Idle Wax Unit.
3. The starter valves allow the air flow to each cylinder to be balanced at the closed throttle position and low throttle opening - less than 5%.

The Symptoms

The symptoms of the SV’s being out of adjustment include:

1. Lumpy idle - not to be confused with the already off-beat idle due to the uneven spacing of the firing pulses of the V4 engine.
2. Hesitant throttle response when opening the throttle from closed.
3. Increased vibration - check the chain/sprocket condition and tension first as the VFR can be quite fussy about an over-tight or too loose chain.

Balancing the Starter Valves – time taken approx 30 mins

This is generally accepted as one the ‘must do’ items on the fuel injected models of VFR, even though it doesn’t appear in the service manuals and not too many dealers appear to do it as routine.

Tools needed:

A Carbtune or similar.
Small diameter Phillips head screwdriver.
7mm spanner.
8mm socket plus extension piece.
2 clamps.
Photo 1

First job is to remove the 2 x 8mm bolts holding the front of the tank down Photo 2. You will probably need an extension to the ratchet to save damaging the tank, and you may consider placing a towel or similar over the tank to prevent scratching it. Be careful not to drop the bolts or washers! Next remove the seat and you will be able to lift the tank at an angle (the base plate moves to accommodate this). If you are able, try placing a nail or hook in the ceiling just above and behind the tank. Then get a piece of old household flex or similar and you can support the front of the tank away from the airbox without having to remove it Photo 3 (don’t lift it as high as in the photo, it can stretch the fuel pipes). Otherwise, you will have to use the 2 tools in the bike toolkit to support the front but beware, it’s not very stable!

Now clamp off the two PAIR valve pipes, one at the front above the cylinder head on the left as you sit on the bike Photo 4 and one at the rear of the airbox on the left as you sit on the bike Photo 5.

Next warm the bike up to normal running temperature (around 75 degrees).

Now you need to pull the vacuum tubes from the airbox sides one by one and connect them to the Carbtune in the correct order, i.e. Pipe 1 to the left Carbtune column, pipe 2 to the next etc. The pipes should have the cylinder number on them, but if you can’t see it, then the order is; rear left #1, forward left #2, rear right #3 and forward right #4 Photo 6, 7. Hang the Carbtune from the throttle by the tie wrap supplied with it to make it easier to read Photo 8.

Note: ignore the extra pipe you can see at the bottom of photo 8 coming off the #3 cylinder, it’s the vacuum pipe for my Scottoiler.

Next, remove the rubber bung covering the access hole to the idle adjuster Photo 9. Insert the small diameter Phillips screwdriver and set the idle speed to 1200rpm ±100 for Fi-W/X models, 1300 rpm ±100 for FI-Y/1 models Photo 10, 11. Note: turning clockwise will increase the idle speed.

Now, adjust the starter valves, which can be found nestling inside the frame on the RHS abeam the idle adjuster. Using the 7mm spanner, adjust each starter valve relative to the vacuum gauge value on #1 cylinder, so that:

#2, second from front screw, is the same as #1
#3, most rearward screw, is 20 ± 5 mmHg lower than #1
#4, most forward screw, is 10 ± 5 mmHg lower than #1
Photo 12,13

Note: turning the screw clockwise decreases the vacuum.

Note: the actual value of the vacuum is not relevant, just the relative differences. If the idle speed varies, go back and set it then start the balancing again. Occasionally blipping the throttle will also help stabilise the values.

Turn the ignition OFF, remove the clamps from the PAIR valves, reconnect the 4 vacuum tubes to the airbox, put the rubber plug back in the hole in the frame, lower and reattach the tank. Then take her out for a blast and see how much smoother she is low down! :D

edit: thanks to Odie for helping with this.