May 3

- Baffling -

DH2 yesterday commented that the most obvious place to check for a fault is the starter relay - for the motor to run, the relay must be engaged - perhaps it got stuck on?

And, having used nothing more than the power of mental thought, he was right - there was continuity across the relay terminals. Still - he has got a brain the size of a planet. But when I stripped everything down, and put power across the relay's coil, it had freed itself up, and gave a very satifying and heavy click as it engaged. And disengaged. And engaged. And disengaged. Weird. I can't detect any stickiness at all - no reluctance to engage or disengage.

I then test the switched circuit relay. That is fine too - a good, proper click when I give it power. I connect everything up as it should be, and start the engine (I'd charged the battery overnight). Engine springs into enthusiastic life.

- misfire -

There is a misfire on cylinder #1. There always has been, occasionally, if the idle speed is set too low, but this is a continous misfire. I swap the injectors. No difference - exhaust header #1 stays stone cold. I swap the coils (each plug has it's own coil). No change. I swap the plugs. No change. I check the air bleed hoses. All tight. The ECU is not reporting any faults. Petrol is definitely getting in there, as occasionally it explodes and causes the throttle body to almost pop out of its rubber mount. A small bell rings in my head - upon close inspection, the #1 TB is sitting proud of the mount, relative to the others. I seat the TB firmly into the mount, and try the engine again. No misfire!

So now, I just have to figure out why it misfires at idle. The std GSXR idles at 1100 rpm hot, and 1800 cold, IIRC, but I have to set the idle at about 1500 hot to prevent the misfire and consequent TB explosion and seperation from mount. Anyone got any ideas? I wonder it someone has fitted some very wild cams to this thing and the idle needs to be higher to compensate. Doesn't seem likely to me. And why would it only affect one cylinder?

May 28

- long time, no see... -

It's been a while since I've ventured into the garage. Having falied the SVA retest 3 weeks ago, I'd decided to have a bit of a break, or I might find myself smashing the car to pieces with a hammer...

- twiddling -

Today, I fixed a couple of little things that had been bugging me. ! was that the FI fault light had come on again, and once again, it was the EXCVA sensor. After lots of fiddling with pulling wires out of the ECU, shorting things and fiddling with resistors, I found that a potential divider across the 3 terminals of the sensor plug in the loom did the trick. In theory, a 1:1 split in the input voltage should have done the trick, in that the manual says that sensor is supposed to see 0.2V to 4.8V, and the input voltage is 4.95 volts. However, a simple potential divider using 2 6k8 resistors didn't work. I took a guess that the ECU also worries about absolute resistance. The manual makes a vague reference to the EXCVA having a resistance of 3k1 ohms at 'the reference position'. So I decreased the resistance on one side of the divider by putting another 6k8 resistor on one side, and that did the trick.

The other thing I did was, having read this TL1000S website, I pulled the clutch position switch sensor wire out of the ECU, just in case that's contributing to the super richness of the engine (the theory being that when the clutch is pulled in on the bike, the ECU switches to a different map, which is presumably only accurately mapped for the no load sites. If the only action you take to bypass the clutch switch in the loom is to short it, then you'd be running this map rather than the one you actually want. There is no evidence to support this on the GSX-R 1000, but it's a possibility)

I think I've figured out the cold idle thing as well. I noticed that when the engine starts up, it always starts with the seconday throttles fully open, and then closes them a little as the engine warms up. There's a linkage that is actuated by the secondary throttles that bears on the secondary idle screw, which in turn opens the main throttle valves a crack wider; but it only comes into play at wide (secondary) throttle angles. Sooooo, I've set the secondary idle screw to a position where the engine will idle at 1800rpm whilst the secondary throttle is open, but once it closes, the engine will idle at the prescribed 1150rpm.

It's hard to tell if I've got it exactly right, as it's a warm day today, and the ECU quite quickly decides that it's OK to close down the secondary throttles.

This page last updated on: Thursday, Aug 24 2006