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Discussion Starter · #1 ·
Unable to find the cause of running on the back cylinder only. What do I do? Run it with the bench setup until hot and see what happens?. Then put it back together, join roadside assistance, and ride it?

I put this up as a post a few weeks ago.
"Started cold ok, backfired once on a warm start. Did about 10klm this morning and it starts running on the back cylinder. Put new plugs in, ran for about a minute on both, then back to 1. The old back plug was almost rich, but the front plug was lean as white. Spark is ok, starts and runs fine on back cylinder with front plug removed. Front plug when fitted and removed is dry. Fueling issue, Caused by electrical issue? Fuel pressure is fine (42) when running on back plug. Gut tells me its something simple, wiring loom problems, dirty or failed electrical connector or injector. It's fitted with a PC3."

Currently set up, and running perfectly, as per 1st photo. There were no fault codes, no dirty or burnt connectors, nothing to help me isolate the issue (and I'm an ex Rank Xerox technician..)

In the 2nd photo, where does that "Y" piece connect?

Thanks, Greg
 

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Under the plastic cover that screws to the front of the tank there will be two short hoses connected to the tank pull the “Y” piece up and connect them.
Get the PC out of the system. Sounds like you’ve established that cylinders have spark. Before you go any further you should get the injectors tested and cleaned. This seems to be the area of grief. Did you swap injectors over to what happens? Have a little squirt bottle of water to spray the headers. This tells you which cylinder is misbehaving. I’m betting the ecu isn’t the problem.
 

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Discussion Starter · #3 ·
The problem at the moment is that there is now no problem and no indication of what it was. It's running perfectly on the "bench" setup, to the point where the headers are within a few degrees C of each other. (I have a temperature "gun" that I use when I'm tuning the old 3 cylinder Laverdas).
 

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The problem at the moment is that there is now no problem and no indication of what it was. It's running perfectly on the "bench" setup, to the point where the headers are within a few degrees C of each other. (I have a temperature "gun" that I use when I'm tuning the old 3 cylinder Laverdas).
 

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I note you have a PCIII installed. I have had 2 PCIIIs go bad on my 998, resulting running on one cylinder only, both time at track days. Dynojet replaced both of them for me (admittedly it was more than 10 years ago).
 

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Discussion Starter · #6 ·
I note you have a PCIII installed. I have had 2 PCIIIs go bad on my 998, resulting running on one cylinder only, both time at track days. Dynojet replaced both of them for me (admittedly it was more than 10 years ago).
Interesting, and timely comment. For some stupid reason I was not factoring the PC3 into my analysis, even though plenty of advice about their reliability. I've got a spare PC5, so I'm going to load it up with my settings, make sure it works on the bike, then put it in a plastic bag in my Givi. Thanks! Greg
 

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Discussion Starter · #8 ·
dont think the pc5 is aplug and play on a 999. have you run the thing without the pc3?
Bugger about the PC5 maybe not being plug'n'play...No, I haven't run it without the PC3, but I will now and make sure it still runs, and then hook it back in again. Then, if/when it happens again, I will disconnect the PC3 and see what happens. Thanks!!!!
 

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Discussion Starter · #9 ·
I'm empathizing with Stray Dog and his 748R running on one cylinder....My 999 is randomly intermittent with the operation of the front injector. Bypassing the PC3 made no difference (Xracer is correct. the PC5 I have is not plug'n'play, wrong plugs...) Bloody thing only ran on 1 cylinder after I connected the CRO, but started running on 2 before I got the setup on the CRO correct. So close! Not easy to swap the injectors as the oem hard fuel hose doesn't permit this.
I've included a couple of screen shots just for the fun of it....
 

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