The CBR250Ri

The Great Bug Hunt

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Neil practicing his piano technique on the crapslop whilst being assaulted by an eyeball-devouring black square
Being the infuriatingly anal perfectionist that he is, Neil decided that getting the CBRi running well was his cue to completely re-write the ECU software. He claimed that the first version was written while he was pissed, which certainly explained some of the problems we’d been having. Version 2.0 of the software was produced without the aid of ethanol, and Neil proudly declared that the routines for controlling the injectors and calculating engine speed from the ignition pulses were much faster than they had been before.

While Neil was screaming for vodka and bashing his head against his laptop in an effort to improve the code, Richard was pushing the CBRi back from the local servo. He’d taken it down there in search of more go-juice, and a power spike in the ignition system reset the ECU and nuked the fuel map. Richard didn’t have his laptop or mobile phone, so he didn’t have much choice but to push the bike home. It’s 1.68km from the servo to Richard’s place, and most of it is uphill. When he recovered from the exertion, he bodgied up a flash card addition to the ECU. The Mk IIa ECU could remember it’s fuel map through resets, power loss or acts of extreme stupidity. Richard also wrote a program to store and modify maps in his Palm Pilot and upload them to the ECU.

The Mk IIa ECU conversing with a crapslop. The fuel map display is just barely visible on the screen.
We loaded Neil’s V2.0 software with high hopes, and were disappointed to find that it controlled the injectors so well that the old maps didn’t work anymore. We tried to tweak them, but without much success. Sometimes the bike would start without any problems, but sometimes it wouldn’t start at all. A bit of stuffing about with an oscilloscope revealed some of the problems. The new code was much more susceptible to noise in the ignition circuit than the old code, which played havoc with the injector timing. V2.0 handled the injectors much faster and more accurately when it was getting the right signal from the ignition pickups, but when it wasn’t getting the right signal it was squirting fuel onto a closed intake valve and the bike ran like a dog. This was most noticeable at low RPMs when the engine was cold, so the CBRi was now almost impossible to start cold and run for any length of time. We were keen to try the new code at high RPMs where any fuelling improvements would be magnified (with a corresponding magnification of horsepower), so we bolted the carburettors back on to get it running and warm. The plan was to quickly convert it back to injection and get back on the road, but our haste had tragic consequences.




Richard and his favorite toy. He only smiles when he's smashing something. (The psychotic gleam in his eyes has been censored) Richard got a tad too enthusiastic about seating the intake stubs in the carb rubbers with his beloved “knockometer” (hammer), and the aluminium manifold literally came apart at the seams. Various repairs were attempted; hot glue, Steve’s tube of Knead-It and finally the MIG welder. None were particularly successful, so it was back to the drawing board for a change of material and some revised geometry. Aluminium, although light, had been a hassle to work with and so the Mk II manifold was welded up out of chunky 2 and 3mm steel plate. It was specifically designed to withstand a psycho belting the crap out of it with a hammer. The main changes from the Mk I were a thinner body profile to bring the injectors closer to the ports and internal strengthening ribs.

The new manifold was fully airtight, unlike the old one, and that made cold starts and low-speed running much easier. In fact, the CBRi now started better than it ever did with carbies, and needed much less fuel than before. However, it also had a tendency to flood, which meant more plug extractions, more skinned knuckles and lots and lots of bad language. It wasn’t long before we discovered that the ECU was sometimes leaving an injector turned on continuously. Occasionally it would flip into a schizophrenic frenzy and trigger the injectors at random. The result was always an oversupply of fuel and often, complete engine hydrolock. More plug extractions, but no bent valves. Thank Saint Soichiro-san for a tough little motor!

While Neil searched the code for the injector control bug and tried to find a solution to the noise problem from the ignition pickups, Richard disappeared into the gloom of his electronics workshop, intent on mayhem and destruction. He emerged some time later proudly displaying the Mk III ECU, a box about twice the size of a pack of smokes. The Mk III does everything the Mk IIa did except take up as much room. Of course, the Mk III still has a blinky LED. We checked with Richard’s psychotherapist, but apparently his fixation is harmless. We still try to keep him away from sharp objects, though. We’d like to confiscate his knockometer as well, but we’re afraid of what he might do if we try.

The Mk II fuel rail mounted on the Mk III manifold. The fuel rail was also working perfectly well as it was, but that didn’t stop Richard from tinkering with it. We keep telling him that if it’s not broken, he shouldn’t play with it, but he doesn’t listen. Anyway, Richard decided that the short sections of fuel line connecting the injectors to the rail were too bodgy. It was probably those hose clamps. Richard hates hose clamps. Steve was in favour of just ditching the clamps and hoping for the best (after all, we’ve always mixed fuel and electrics before and nothing has exploded yet), but he was outvoted. A new fuel rail was soldered up from 10mm copper pipe such that the injectors would plug straight into it. A sprinkling of rubber gaskets to keep everything sealed, a couple of springs to hold the whole shebang together, et voila – the Mk II fuel rail. It only leaks a little bit. The main advantage of the Mk II is the fact that it is solidly mounted onto the manifold rather than being a press fit.

Installed in the bike. The space savings over the carbies are incredible. At time of writing, Neil is embroiled in a fight to the death with that great nemesis of all post-grad students called Thesis. He is also incapacitated by a mystery virus, which may be unknown to science but is far more likely to be an extreme variety of procrastination. Richard is slaving away in the salt mines of academia, working 18-hour days for very little money and absolutely no recognition, and Steve is being paid by the Government to sit on his bum and pick his nose. It’s a tough job, but someone’s gotta do it, and let’s face it, he’s not qualified for much more.


The CBRi remains temporarily bug-ridden and off the road, but as soon as Neil stops coughing up green slime, when Richard is dragged from his office like a white and pasty grub being plucked from a rotten log, and by the time the Queensland Government can function without Steve’s invaluable (cough cough) assistance, progress will continue.

Stay tuned.