The front header pipe, oil filter and crankcase always looked really vulnerable, so I have installed a lovely alloy bash plate. Was a BITCH to fit, because the captive nut that the exhaust mounts on (where the bash plate happens to also need mounting on) was lock-tighted in so hard that it spun. I had to crush the outer captive nut holder with vice grips to get it undone. Needless to say the bolt thread was damaged and I had to run a tap through the not so captive nut and then find a new slightly longer bolt because of the extra thickness the bash plate added. Turns out an XR650R chain adjuster was just perfect :-). What should have been a 20 minute job turned into 2 hours! Anyway, got it sorted in the end!

Good news! after messing about turning the ignition on and off while riding the bike, and the problem temporarily going away, I decided to remove the fuel pump and inspect it again. Before I removed it I did a flow test and got the usual 300ml with three cycles of the ignition. No change there. I removed the pump, disassembled and very carefully reassembled. The only thing I did differently was I mated the pump motor with the top high pressure fuel filter before I put the mated the bottom housing and inlet filter. It felt like it had a nice tight seal with the o ring on the pump motor outlet and high pressure fuel filter top. I refitted the pump and to my amazement all the issues have gone away. I rode it with a fairly low fuel level, two bars on the gauge and no issues, then filled it up and again all good. The bikes performance has improved dramatically now, much much faster and no flat spots anywhere. All I can think is that while the pump had good fuel flow it didn’t have good pressure and was bleeding off pressure somewhere from one of the o rings in the fuel pump housings. Maybe I pinched an o ring last time I assembled? Although its a bit of a mystery I am stoked that its finally fixed. I rode it today for 100kms and no issues at all.
On a side note, next time I ever have to work on a motorcycle fuel injection system I am going to buy a fuel pressure gauge. I think if I had one of those to start with I would have saved myself a lot of time.

So, after last weekends issues, and some good advice, I decided that the problem running issues were most likely caused by a non venting fuel cap. It made perfect sense to me. I removed the fuel tank cap yesterday and dismantled. Apart from some superficial corrosion and some water, it all seemed OK. I reassembled and took the bike out for a test ride today. All seemed ok at first, until after about an hour of fairly fast riding the same issue appeared again, low power, unresponsive at wide open throttle at high RPM, just like it is starving for fuel. Once again I was near a petrol station, so I did the same as last time, pulled in and topped off the tank. Once again, all the issues went away again. Interestingly enough it took almost exactly the same amount of fuel as last time, 8.7 litres. I’m now completely baffled as to what the problem is. I’m going to ride the bike for a bit because I am fed up with working on it. The next thing I will probably do is do a fuel pump flow test with less than 10 litres fuel in the tank.

Took it for a test ride and there was a significant improvement in performance, a lot smoother at small throttle openings. I was feeling relieved that finally the bike was as Suzuki intended it to be. Then after a couple of KMs of slow riding at 50km/h the bike started behaving badly, intermittent power delivery at small throttle openings, so bad I thought it was going to stop. It felt similar to the fuelpump flow issues I experienced earlier. I pulled into a petrol station and even though the fuel gauge said I had 3/4 of a tank, I topped it off. It took 8.9 litres, so definitely wasn’t about to run out. After filling the tank everything went back to normal. All running perfectly. I am now wondering what all that was about? Does the fuel tank level have any effect on the amount of fuel pumped? I wouldn’t expect it too, but one of the fuel pump tests specified a large amount of fuel in the tank. I’m going to do another fuel pump flow test later.

I installed the new fuel injectors today. Took me three attempts to finish the job properly. In fact the whole thing was a pain in the arse.
The front hose clamp that holds the air box to the throttle body is a bitch to get at and was SUPER tight. I ended up removing the air box without disconnecting it, then still couldn’t get the hose clamp undone, so I used my Dremel thingy to cut the hose clamp screw. What a pain.
I replaced the injectors, reassembled and discovered that I hadn’t put the rear cylinder injector in properly so fuel leaked everywhere.
Disassembled again and corrected that, reassembled and got C49 error code. I disassembled yet again and discovered I had forgotten to plug in one of the many sensors. So yet again I had to disassemble, plug the sensor in and reassemble yet again.
Finally it’s all done. The weather was rubbish so I didn’t get a chance to test ride, but it did start and run well.
Fingers crossed when the weather improves and I can test ride it and there is some improvement.